release: 0.114.3 (improvement/e49-refusal-contract)

A refusal's detail now stands where it is sent (HTTPException's detail,
a JSONResponse's "detail") or is returned by a factory that only ever is,
with any spread before its code and reason, so no spread can replace
them. The scan follows no variable and no kwargs any more; what it cannot
read in a reason (a lambda's or comprehension's name, a nonlocal or
global, a local that reaches itself, a constant or map changed elsewhere,
an app import it cannot resolve) is reported. The detail guard reads the
same slots and fails on anything but a code dict or a factory's call.

CHANGELOG.md

@@ -7,6 +7,55 @@ edit the release notes and re-run the generator.
 
 Upgrading, pinning a version and rolling back: [docs/self-hosting.md](docs/self-hosting.md#upgrading).
 
+## 0.114.3 — 2026-11-01
+
+### Fixed
+
+- Editing a file that is neither video nor audio now says why it can't be done, instead of a generic error.
+
+## 0.114.2 — 2026-10-30
+
+### Fixed
+
+- Security: a library the sign-in relies on is updated, closing two published vulnerabilities.
+
+## 0.114.1 — 2026-10-30
+
+### Fixed
+
+- Notifications follow a language switch: a notice on screen and every row in the notification center are said again in the new language, their buttons too.
+
+## 0.114.0 — 2026-10-29
+
+### New
+
+- Notifications: what asks for you comes first, then everything else as one stream, newest first. Read notices older than a week fold under Earlier, and Back returns to the row you left.
+
+### Fixed
+
+- Plex: a progress save sent just before an episode ends no longer leaves it unwatched, and a refused finish no longer sticks.
+- After a dialog closes, the keyboard focus returns to where it was, also inside a menu that stays open.
+
+## 0.113.0 — 2026-10-28
+
+### New
+
+- The address names what you see: tabs, list views, sorts and searches (the live YouTube search too), the YouTube player and the file viewer. A reload, a bookmark or a shared link opens the same view.
+- A link to a video reopens the player over its page once; Back closes it. A video the page no longer lists plays on its own and says so.
+
+### Fixed
+
+- Back and Forward step through the views as you saw them, across dialogs, players and reloads: a reload under an open player no longer leaves a Back step that does nothing.
+- Signed out on a Plex page, the sign-in card could show a button with no text.
+- The channel page's address names the channel and its own view, not the page under it.
+- A reload during a Plex binge reopens the episode playing now, not the one it started from.
+
+## 0.112.1 — 2026-10-27
+
+### Fixed
+
+- Security: the sign-in library is updated, closing two published vulnerabilities.
+
 ## 0.112.0 — 2026-10-25
 
 ### New

CLAUDE.md

@@ -105,7 +105,7 @@ CQRS, a repository/DI framework, a router library, a generic CRUD-router factory
 | Ownership check                      | `userscope.owned_by` (a filter) / `owned_row` (a row by id): a unit's `queries.own_x` returns None and its route answers `not_found`; a core route `owned_or_404`. A composite rule (own or shared, built-in or own) says so in its `queries` | an inline owner filter — `Model.user_id == …`, an alias's, `.in_()`, `filter_by(user_id=…)` (fence-held, every module) — or a `db.get` and a compare where `owned_row` fits                 |
 | Admin gate import                    | `app.auth`                                                                                                                                                                                                                                    | the `app.routes.admin` re-export                                                                                                                                                            |
 | Upstream failure status              | `422` with JSON detail                                                                                                                                                                                                                        | `502` (reserve 502 for raw byte-proxies)                                                                                                                                                    |
-| User-facing error                    | structured `detail` (`{code, reason}`)                                                                                                                                                                                                        | a bare English string under a bilingual UI                                                                                                                                                  |
+| User-facing error                    | structured `detail` (`{code, reason}`), its sentence named in `lib/api/refusalCodes.ts` (contract-held)                                                                                                                                       | a bare English string under a bilingual UI                                                                                                                                                  |
 | Mutation response                    | `{"ok": true, …}` (`{"deleted": id}`), test-held                                                                                                                                                                                              | a bare `{"unsubscribed"}`/`{"cleared": n}`, no `ok`                                                                                                                                         |
 | Transaction commit                   | the handler commits; a unit's `service` and every helper `flush` (fence-held, every module)                                                                                                                                                   | a helper that commits — only a listed one (what owns its session, or a core step that must land whatever its caller does next), each with its reason: the fence's `UNIT_COMMITS` / `CORE_COMMITS`, a route's `COMMITTING_HELPERS` (`test_route_conventions`) |
 | Admin knob storage                   | `sysconfig` (values)                                                                                                                                                                                                                          | env / `app_state` / a table of its own (the job intervals had one)                                                                                                                          |
@@ -115,6 +115,7 @@ CQRS, a repository/DI framework, a router library, a generic CRUD-router factory
 | FE keyboard shortcut                 | a row in `lib/keymap.ts` + `dispatch()`                                                                                                                                                                                                       | a private `keydown` listener with its own key literals                                                                                                                                      |
 | FE list/grid keys                    | `NavGrid`/`keyboardNav` + `navItemAttrs` + `data-nav-open`                                                                                                                                                                                    | a private arrow-key / roving-tabindex handler                                                                                                                                               |
 | FE view push (history)               | `rememberNavPosition()` right before `history.pushState`                                                                                                                                                                                      | a push that forgets: Back strands focus on `<body>`                                                                                                                                         |
+| FE view state                        | the module's URL codec: its keys in `urlKeys` (`module.ts`), read and written by `lib/<id>UrlState.ts` through `useUrlMirror` (contract-held, `e2e/bookmark.spec.ts`)                                                                         | `useState` / sessionStorage alone: a reload, a bookmark or a shared link loses the view                                                                                                     |
 | FE a page's header content           | the page renders it into the floating header itself (`PageHeader`, `ui/PageShell`)                                                                                                                                                            | a `page === …` branch in the shell's header, or a bridge carrying a page's state up to it                                                                                                   |
 | FE module store                      | its definition's `Store` (`module.ts`), mounted at the root by `ModuleStores`; it reads no other module's store (contract-held)                                                                                                               | a provider hand-nested in `main.tsx`                                                                                                                                                        |
 | FE saved views                       | the module's own store from `features/filters` (`createSavedViewsStore` + `useSavedViewsStore`)                                                                                                                                               | one store switched by the active page — every visit elsewhere reset it                                                                                                                      |

VERSION

@@ -1 +1 @@
-0.112.0
+0.114.3

backend/app/downloads/clip.py

@@ -22,6 +22,7 @@ import json
 import math
 import re
 from pathlib import Path
+from typing import Literal
 
 from app.downloads.edit import AAC_ARGS, EVEN_FRAME, INPUT_GUARD, X264_ARGS
 from app.plex.sync import HDR_TRANSFERS
@@ -57,12 +58,27 @@ _CROP_ASPECTS = (0.25, 4.0)
 _EDGE_SLACK = 1e-3
 
 
+# Every reason a clip is refused; the UI names each one (`clip.errors.<reason>`, held by the frontend's
+# backendIds contract, which reads this Literal).
+ClipReason = Literal[
+    "bad_source",
+    "bad_range",
+    "too_short",
+    "too_long",
+    "bad_audio",
+    "bad_crop",
+    "not_found",
+    "media_missing",
+    "past_end",
+]
+
+
 class ClipError(Exception):
     """A clip request that cannot be cut; `reason` is an i18n-mappable key, `params` the numbers its
     message names (the cap itself, so the client never says a stale one)."""
 
-    def __init__(self, reason: str, **params: float):
-        self.reason = reason
+    def __init__(self, reason: ClipReason, **params: float):
+        self.reason: ClipReason = reason
         self.params = params
         super().__init__(reason)
 

backend/app/downloads/credentials.py

@@ -25,6 +25,7 @@ Security controls enforced here:
 
 import os
 from pathlib import Path
+from typing import Literal
 
 from sqlalchemy import select
 from sqlalchemy.orm import Session
@@ -163,9 +164,18 @@ def get_credential(db: Session, user_id: int, host_key: str) -> DownloadCredenti
     ).scalar_one_or_none()
 
 
+# Every reason a pasted cookies.txt is refused; the UI names each one (`downloads.errors.cookies.<reason>`,
+# held by the frontend's backendIds contract, which reads this Literal).
+CookieReason = Literal["empty", "format"]
+
+
 class InvalidCookies(ValueError):
     """The pasted cookies aren't a usable Netscape cookies.txt — surfaced as a 400 by the route."""
 
+    def __init__(self, reason: CookieReason):
+        super().__init__(reason)
+        self.reason: CookieReason = reason
+
 
 def validate_cookies(raw: str) -> str:
     """Sanity-check a pasted cookies.txt (Netscape format) and return the cleaned text. yt-dlp reads

backend/app/downloads/folders.py

@@ -24,6 +24,7 @@ kept it — and its `ready_at`, the moment it finished (`stamp_done`).
 
 from datetime import datetime, timedelta, timezone
 from enum import StrEnum
+from typing import Literal
 from urllib.parse import urlsplit
 
 from sqlalchemy import select
@@ -181,12 +182,22 @@ def stamp_done(db: Session, job: DownloadJob) -> None:
     job.expiry_warned = False
 
 
+# Every folder change the rules refuse, answered as a generic refusal; the UI names each one
+# (`errors.refused.<reason>`, held by the frontend's backendIds contract, which reads this Literal).
+FolderReason = Literal[
+    "file_folder_gone",
+    "file_folder_name_taken",
+    "file_folder_not_its_source",
+    "file_folder_not_own",
+]
+
+
 class FolderError(Exception):
     """A folder change the rules refuse; `reason` is the refusal the route answers with."""
 
-    def __init__(self, reason: str) -> None:
+    def __init__(self, reason: FolderReason) -> None:
         super().__init__(reason)
-        self.reason = reason
+        self.reason: FolderReason = reason
 
 
 def own_folder(db: Session, user_id: int, folder_id: int, *, hold: bool = True) -> FileFolder:

backend/app/downloads/quota.py

@@ -20,6 +20,7 @@ their output's real size before it is placed. Edit jobs do not consult it at all
 """
 
 from dataclasses import dataclass
+from typing import Literal
 
 from sqlalchemy import and_, func, or_, select
 from sqlalchemy.orm import Session
@@ -50,11 +51,16 @@ class QuotaLimits:
     unlimited: bool
 
 
-class QuotaExceeded(Exception):
-    """Raised by check_enqueue; `reason` is one of max_jobs|max_bytes (i18n key on the client)."""
+# Every cap a download can hit; the UI names each one (`downloads.errors.quota.<reason>`, held by the
+# frontend's backendIds contract, which reads this Literal).
+QuotaReason = Literal["max_jobs", "max_bytes"]
 
-    def __init__(self, reason: str, limit: int, current: int):
-        self.reason = reason
+
+class QuotaExceeded(Exception):
+    """Raised by check_enqueue; `reason` names the cap it hit (an i18n key on the client)."""
+
+    def __init__(self, reason: QuotaReason, limit: int, current: int):
+        self.reason: QuotaReason = reason
         self.limit = limit
         self.current = current
         super().__init__(f"download quota exceeded: {reason} ({current}/{limit})")

backend/app/downloads/service.py

@@ -10,6 +10,7 @@ handler); the folder, link and quota writes are `folders`, `links` and `quota`.
 
 import uuid
 from datetime import datetime, timezone
+from typing import Literal
 
 from sqlalchemy import delete as delete_rows
 from sqlalchemy import func, select, update
@@ -39,11 +40,16 @@ from app.plex import paths as plex_paths
 from app.userscope import owned_by, owned_row
 
 
-class EditError(Exception):
-    """Bad edit request (empty spec / source not ready); `reason` is an i18n-mappable key."""
+# Every reason an edit is refused; the UI names each one (`downloads.errors.edit.<reason>`, held by
+# the frontend's backendIds contract, which reads this Literal).
+EditReason = Literal["source_not_ready", "not_media", "empty_edit"]
 
-    def __init__(self, reason: str):
-        self.reason = reason
+
+class EditError(Exception):
+    """Bad edit request (empty spec / source not ready / not media); `reason` names the sentence."""
+
+    def __init__(self, reason: EditReason):
+        self.reason: EditReason = reason
         super().__init__(reason)
 
 

backend/app/downloads/urlguard.py

@@ -33,24 +33,33 @@ user-controlled destination to guard.
 
 import ipaddress
 import socket
+from typing import Literal
 from urllib.parse import urlparse
 
 # Reason codes travel to the client inside the structured 422 detail, so they are part of the API
-# vocabulary (frontend `localizeDetail`) — keep them stable.
-REASON_SCHEME = "scheme"  # not http(s)
-REASON_NO_HOST = "no_host"  # URL carries no hostname
-REASON_MALFORMED = "malformed"  # unparseable authority or port; urlparse raises late, so guard it
-REASON_UNRESOLVABLE = "unresolvable"  # DNS said nothing (honest: not the same as "blocked")
-REASON_PRIVATE = "private"  # resolves into a network the server must not fetch from
+# vocabulary — keep them stable. The UI names each one (`downloads.errors.urlBlocked.<reason>`, held by
+# the frontend's backendIds contract, which reads this Literal).
+UrlBlockedReason = Literal["scheme", "no_host", "malformed", "unresolvable", "private"]
+REASON_SCHEME: UrlBlockedReason = "scheme"  # not http(s)
+REASON_NO_HOST: UrlBlockedReason = "no_host"  # URL carries no hostname
+REASON_MALFORMED: UrlBlockedReason = (
+    "malformed"  # unparseable authority or port; urlparse raises late
+)
+REASON_UNRESOLVABLE: UrlBlockedReason = (
+    "unresolvable"  # DNS said nothing (not the same as "blocked")
+)
+REASON_PRIVATE: UrlBlockedReason = (
+    "private"  # resolves into a network the server must not fetch from
+)
 
 
 class BlockedUrl(Exception):
     """A user-supplied URL that must not be fetched server-side. ``reason`` is one of the
     REASON_* codes above."""
 
-    def __init__(self, reason: str):
+    def __init__(self, reason: UrlBlockedReason):
         super().__init__(reason)
-        self.reason = reason
+        self.reason: UrlBlockedReason = reason
 
 
 def _is_forbidden(ip: ipaddress.IPv4Address | ipaddress.IPv6Address) -> bool:

backend/app/plex/service.py

@@ -6,9 +6,9 @@ The rest of the mirror's writes stay with the sync (`plex.sync`): a collection's
 after a write-back, its local cleanup after a delete.
 """
 
-from datetime import datetime, timezone
+from datetime import datetime, timedelta, timezone
 
-from sqlalchemy import CursorResult, delete, func, select, update
+from sqlalchemy import CursorResult, delete, func, or_, select, update
 from sqlalchemy.dialects.postgresql import insert as pg_insert
 from sqlalchemy.orm import Session
 
@@ -271,6 +271,10 @@ def reorder_playlist(db: Session, pl: PlexPlaylist, rating_keys: list[str]) -> N
 
 # --- a user's watch state --------------------------------------------------------------------
 
+# How long after a watched mark a mid-item position is read as the finishing player's late tick
+# (`checkpoint`): the tick is every 10 s, plus the request's own latency and a retry.
+_LATE_CHECKPOINT_S = 30
+
 
 def mark_finished(db: Session, user_id: int, item_id: int, now: datetime) -> bool:
     """Mark the item watched (position cleared) and say whether THIS call made it so. Two near-end
@@ -352,16 +356,33 @@ def checkpoint(
     now: datetime,
     *,
     dirty: bool,
-) -> PlexState:
-    """Record a resume position. `dirty` marks it not yet mirrored to Plex — set before a push, so
-    the reconcile re-pushes it if the push fails and the push can settle it once Plex confirms."""
+) -> bool:
+    """Record a resume position, and say whether it was recorded. `dirty` marks it not yet mirrored
+    to Plex — set before a push, so the reconcile re-pushes it if the push fails and the push can
+    settle it once Plex confirms.
+
+    Not onto a row marked watched in the last `_LATE_CHECKPOINT_S`: that position is the player's
+    tick sent just before its own finish (or a mark from another tab), and writing it made a watched
+    item in progress again — on Plex too, through the resume push it carried. Decided by the write
+    itself, since the mark can commit between any read here and the write. A rewatch is checkpointed
+    as before once the mark is that far behind it."""
     st = state_row(db, user, item_id, st)
-    st.position_seconds = position
-    st.progress_updated_at = now
+    values: dict[str, object] = {"position_seconds": position, "progress_updated_at": now}
     if dirty:
-        st.synced_to_plex = False
+        values["synced_to_plex"] = False
+    not_just_finished = or_(
+        PlexState.status != "watched",
+        PlexState.watched_at.is_(None),
+        PlexState.watched_at <= now - timedelta(seconds=_LATE_CHECKPOINT_S),
+    )
+    result = db.execute(
+        update(PlexState)
+        .where(PlexState.id == st.id, not_just_finished)
+        .values(values)
+        .execution_options(synchronize_session="fetch")
+    )
     db.flush()
-    return st
+    return isinstance(result, CursorResult) and result.rowcount > 0
 
 
 def forget_state(db: Session, st: PlexState) -> None:

backend/app/plex/stream.py

@@ -66,7 +66,9 @@ _SESSION_IDLE_S = 600  # reap a session with no access for this long
 # restart leaves them behind like any other. `sweep_orphans` deletes ONLY names
 # matching one of those two shapes: `_HLS_ROOT` is admin-configurable (PLEX_HLS_DIR), so it may
 # legitimately point at a shared scratch path we do not own, and a blanket "delete every directory
-# under the root" would take the neighbours with it.
+# under the root" would take the neighbours with it. A torn-down session's directory is renamed to
+# its own name + `_TOMB` + 8 hex digits before it is deleted (see `_detach`), so a crash between the
+# two leaves a name this sweep still recognises.
 #
 # The KEY is anchored to digits (a Plex rating_key is a number) — that is what keeps foreign names
 # out. A `.+` there let `snapshot_2024_backup_+1.00` through, and pairing `.+` with an optional tail
@@ -74,8 +76,10 @@ _SESSION_IDLE_S = 600  # reap a session with no access for this long
 # non-numeric rating_key would merely leave its directory unswept, which is the safe direction to
 # fail. Covered by test_plex_stream.py — this regex is the only thing standing between the sweep
 # and someone else's data.
+_TOMB = ".dead-"
 _SESSION_DIR_RE = re.compile(
-    r"^\d+_\d+(_[^_]+_[+-]\d+\.\d{2})?$|^\d+_u\d+_\d+_[^_]+_[+-]\d+\.\d{2}$"
+    r"^\d+_\d+(_[^_]+_[+-]\d+\.\d{2})?$"
+    rf"|^\d+_u\d+_\d+_[^_]+_[+-]\d+\.\d{{2}}({re.escape(_TOMB)}[0-9a-f]{{8}})?$"
 )
 # When this process started. `sweep_orphans` only deletes directories older than this: everything
 # newer belongs to a session THIS run created, and since `start_session` reuses a directory path
@@ -93,7 +97,7 @@ _MTIME_GRACE_S = 2.0
 
 _lock = threading.Lock()
 # Keyed by VIEWER and item, (user_id, rating_key). Keyed by the item alone, a second account opening
-# the same film `_kill`ed the first one's session: the displaced viewer got a 404, reclaimed at its
+# the same film tore down the first one's session: the displaced viewer got a 404, reclaimed at its
 # playhead, and so evicted the other in turn — two people could not watch one film at once. (One
 # account on two devices still shares a session; that case ends in the player's bounded reclaim.)
 _sessions: dict[tuple[int, str], "HlsSession"] = {}
@@ -641,29 +645,82 @@ def _probe_first_pts(seg: Path) -> float | None:
     return None
 
 
-def _kill(s: HlsSession) -> None:
+# Teardown is split in two, because every segment request and checkpoint takes `_lock`: waiting up to
+# 3 s for an ffmpeg to exit and deleting a whole segmented film under it stalled every other
+# viewer's playback for one viewer's seek or one reap pass. `_detach` (under the lock) signals the
+# process and renames its directory aside — so the deletion can never hit a NEW session that reuses
+# the path — and `_finish` (after the lock is released) waits and deletes.
+#
+# What the rename cannot cover is the dying ffmpeg itself: it writes by path, so until it has exited
+# it can still put a segment, or its final ENDLIST playlist, into a new session's directory on the
+# same path. `_dying` remembers it by that path, and `_spawn` waits it out — under the lock, on
+# purpose — before it creates the directory again.
+_dying: dict[Path, subprocess.Popen] = {}
+
+
+def _await_exit(key: str, proc: subprocess.Popen) -> None:
     try:
-        s.proc.terminate()
         try:
-            s.proc.wait(timeout=3)
+            proc.wait(timeout=3)
         # silent-ok: the escalation IS the handling. A transcode that ignores TERM for three
         # seconds gets KILL, which is exactly what this branch does.
         except subprocess.TimeoutExpired:
-            s.proc.kill()
+            proc.kill()
     except Exception as exc:  # noqa: BLE001 — teardown finishes whatever the process does
         # Not nothing: what survives this is an ffmpeg nobody owns any more, holding a VAAPI
         # handle and a core, and the transcode cap that is supposed to bound them counts rows in
         # `_sessions` rather than processes. One line is the only way that ever surfaces.
+        log.info(
+            "could not stop the transcode process",
+            extra=logs.event("plex.stream.kill_failed", key=key, reason=type(exc).__name__),
+        )
+
+
+def _detach(s: HlsSession) -> tuple[HlsSession, Path | None]:
+    """Caller holds _lock and has taken `s` out of `_sessions`. Hand the result to `_finish` once the
+    lock is released."""
+    try:
+        s.proc.terminate()
+    except Exception as exc:  # noqa: BLE001 — teardown finishes whatever the process does
         log.info(
             "could not stop the transcode process",
             extra=logs.event("plex.stream.kill_failed", key=s.key, reason=type(exc).__name__),
         )
-    shutil.rmtree(s.dir, ignore_errors=True)
+    _dying[s.dir] = s.proc
+    tomb = s.dir.with_name(f"{s.dir.name}{_TOMB}{secrets.token_hex(4)}")
+    try:
+        s.dir.rename(tomb)
+    # silent-ok: nothing on disk (ffmpeg died before writing, or a sweep took it) — nothing to delete.
+    except FileNotFoundError:
+        return s, None
+    except OSError as exc:
+        # Cannot be moved aside, so it cannot be deleted outside the lock either: the path may be a
+        # new session's a moment from now. Deleted here instead, the old way.
+        log.info(
+            "a session directory could not be moved aside; deleted under the lock",
+            extra=logs.event("plex.stream.tomb_failed", key=s.key, reason=type(exc).__name__),
+        )
+        shutil.rmtree(s.dir, ignore_errors=True)
+        return s, None
+    return s, tomb
 
 
-def _enforce_caps(user_id: int, max_transcodes: int, max_sessions: int) -> None:
-    """Caller holds _lock. Three bounds, applied after a session is registered, each dropping the
-    least recently accessed sessions over it:
+def _finish(doomed: "list[tuple[HlsSession, Path | None]]") -> None:
+    """The slow half of a teardown, called WITHOUT `_lock`."""
+    for s, tomb in doomed:
+        _await_exit(s.key, s.proc)
+        with _lock:
+            if _dying.get(s.dir) is s.proc:
+                del _dying[s.dir]
+        if tomb is not None:
+            shutil.rmtree(tomb, ignore_errors=True)
+
+
+def _enforce_caps(
+    user_id: int, max_transcodes: int, max_sessions: int
+) -> "list[tuple[HlsSession, Path | None]]":
+    """Caller holds _lock, and `_finish`es what this returns once it has released it. Three bounds,
+    applied after a session is registered, each dropping the least recently accessed sessions over it:
 
     * this account's own sessions (`_MAX_SESSIONS_PER_USER`) — first, so a single account filling the
       box evicts itself before anyone else;
@@ -676,6 +733,8 @@ def _enforce_caps(user_id: int, max_transcodes: int, max_sessions: int) -> None:
     and the player restarts at the playhead, so from the server nothing failed — and "my film keeps
     rebuffering" has no other explanation anywhere, hence the line."""
 
+    doomed: list[tuple[HlsSession, Path | None]] = []
+
     def cull(pool: list[tuple[tuple[int, str], HlsSession]], cap: int, bound: str) -> None:
         if len(pool) <= cap:
             return
@@ -690,12 +749,13 @@ def _enforce_caps(user_id: int, max_transcodes: int, max_sessions: int) -> None:
                     sessions=len(pool),
                 ),
             )
-            _kill(sess)
             _sessions.pop(reg, None)
+            doomed.append(_detach(sess))
 
     cull([kv for kv in _sessions.items() if kv[0][0] == user_id], _MAX_SESSIONS_PER_USER, "user")
     cull([kv for kv in _sessions.items() if kv[1].transcode], max_transcodes, "transcode")
     cull(list(_sessions.items()), max_sessions, "total")
+    return doomed
 
 
 def start_session(
@@ -759,68 +819,79 @@ def start_session(
         # can't starve the co-located API/playback. preexec_fn runs in the forked child (POSIX); on a
         # platform without fork (the API always runs in a Linux container in prod) it's simply omitted.
         preexec = _sw_child_preexec if (transcode and not hw and os.name == "posix") else None
-        with _lock:
-            if replace_only is not None and _sessions.get(reg) is not replace_only:
-                return None  # superseded/culled while we waited out of lock — don't clobber the newer one
-            old = _sessions.pop(reg, None)
-            if old is not None:
-                _kill(old)
-            shutil.rmtree(directory, ignore_errors=True)
-            directory.mkdir(parents=True, exist_ok=True)
-            proc = subprocess.Popen(
-                _ffmpeg_cmd(
-                    src,
-                    start_s,
+        doomed: list[tuple[HlsSession, Path | None]] = []
+        # Finished even when the new session fails to start (no space, no ffmpeg, a DB error): what
+        # was moved aside under the lock is otherwise left for a restart's sweep.
+        try:
+            with _lock:
+                if replace_only is not None and _sessions.get(reg) is not replace_only:
+                    return None  # superseded/culled while we waited out of lock — don't clobber the newer one
+                old = _sessions.pop(reg, None)
+                if old is not None:
+                    doomed.append(_detach(old))
+                # An ffmpeg still exiting from THIS path (the old session, or one stopped a moment ago)
+                # would write into the directory about to be made; see `_dying`.
+                prev = _dying.pop(directory, None)
+                if prev is not None:
+                    _await_exit(key, prev)
+                shutil.rmtree(directory, ignore_errors=True)
+                directory.mkdir(parents=True, exist_ok=True)
+                proc = subprocess.Popen(
+                    _ffmpeg_cmd(
+                        src,
+                        start_s,
+                        directory,
+                        audio_ord,
+                        aoff,
+                        audio_langs if is_multi else None,
+                        transcode=transcode,
+                        hw=hw,
+                        tonemap=tonemap,
+                        preset=preset,
+                        crf=crf,
+                        max_height=max_height,
+                        loudnorm=loudnorm,
+                    ),
+                    stdout=subprocess.DEVNULL,
+                    stderr=subprocess.DEVNULL,
+                    preexec_fn=preexec,
+                )
+                s = HlsSession(
+                    key,
                     directory,
-                    audio_ord,
-                    aoff,
-                    audio_langs if is_multi else None,
+                    proc,
+                    start_s,
+                    variants,
                     transcode=transcode,
                     hw=hw,
                     tonemap=tonemap,
-                    preset=preset,
-                    crf=crf,
-                    max_height=max_height,
-                    loudnorm=loudnorm,
-                ),
-                stdout=subprocess.DEVNULL,
-                stderr=subprocess.DEVNULL,
-                preexec_fn=preexec,
-            )
-            s = HlsSession(
-                key,
-                directory,
-                proc,
-                start_s,
-                variants,
-                transcode=transcode,
-                hw=hw,
-                tonemap=tonemap,
-                user_id=user_id,
-            )
-            _sessions[reg] = s
-            # The one line that says which pipeline a session actually got. Everything downstream
-            # — the cap, the HW→SW fallback, the subtitle offset — is about this choice, and until
-            # now it was only inferable from the ffmpeg command nobody keeps.
-            log.info(
-                "an HLS session started",
-                extra=logs.event(
-                    "plex.stream.session_started",
-                    key=key,
-                    transcode=transcode,
-                    hw=hw,
-                    tonemap=tonemap,
-                    variants=len(variants or ()),
-                    start_s=round(start_s, 1),
-                ),
-            )
-            # Admin-configurable caps (Configuration → Plex); at least 1 each so playback can't be
-            # capped to zero.
-            _enforce_caps(
-                user_id,
-                max(1, sysconfig.get_int(db, "plex_max_transcodes")),
-                max(1, sysconfig.get_int(db, "plex_max_sessions")),
-            )
+                    user_id=user_id,
+                )
+                _sessions[reg] = s
+                # The one line that says which pipeline a session actually got. Everything downstream
+                # — the cap, the HW→SW fallback, the subtitle offset — is about this choice, and until
+                # now it was only inferable from the ffmpeg command nobody keeps.
+                log.info(
+                    "an HLS session started",
+                    extra=logs.event(
+                        "plex.stream.session_started",
+                        key=key,
+                        transcode=transcode,
+                        hw=hw,
+                        tonemap=tonemap,
+                        variants=len(variants or ()),
+                        start_s=round(start_s, 1),
+                    ),
+                )
+                # Admin-configurable caps (Configuration → Plex); at least 1 each so playback can't be
+                # capped to zero.
+                doomed += _enforce_caps(
+                    user_id,
+                    max(1, sysconfig.get_int(db, "plex_max_transcodes")),
+                    max(1, sysconfig.get_int(db, "plex_max_sessions")),
+                )
+        finally:
+            _finish(doomed)
         return s
 
     s = _spawn(*_select_encode(db, item, transcode, src))
@@ -974,6 +1045,11 @@ def artifact_may_arrive(s: "HlsSession", filename: str) -> bool:
     # session, absent for a single-audio one.
     if variant not in (s.variants or (None,)):
         return False
+    # And the name must be the one ffmpeg SPELLS for that sequence: `int()` also reads `seg_007.ts`
+    # and a non-ASCII digit run as a sequence the session may have reached, and neither file is
+    # ever written — a yes there parked the request for the whole wait.
+    if filename != segment_name(seq, variant):
+        return False
     if seq == 0:
         return True
     try:
@@ -1108,16 +1184,16 @@ def reap_idle(finished_idle_s: float = _FINISHED_IDLE_S) -> int:
     `reap_abandoned` bought the same safety by keeping every finished session for ten minutes — each
     one a whole segmented copy of the film on a volume shared with the download center."""
     now = time.time()
-    dropped = 0
+    doomed: list[tuple[HlsSession, Path | None]] = []
     with _lock:
         for reg, s in list(_sessions.items()):
             done = s.proc.poll() is not None
             idle = now - s.last_access
             if idle > _SESSION_IDLE_S or (done and idle > finished_idle_s):
-                _kill(s)
                 _sessions.pop(reg, None)
-                dropped += 1
-    return dropped
+                doomed.append(_detach(s))
+    _finish(doomed)
+    return len(doomed)
 
 
 def stop_session(user_id: int, key: str, session_id: str) -> bool:
@@ -1132,8 +1208,9 @@ def stop_session(user_id: int, key: str, session_id: str) -> bool:
         s = _sessions.get((user_id, key))
         if s is None or s.id != session_id:
             return False
-        _kill(s)
         _sessions.pop((user_id, key), None)
+        doomed = [_detach(s)]
+    _finish(doomed)
     return True
 
 

backend/app/reader/service.py

@@ -9,7 +9,7 @@ unique key, a row lock taken before a presence check. The comfort shelf's writes
 
 from datetime import datetime, timezone
 
-from typing import cast
+from typing import Literal, cast
 
 from sqlalchemy import Table, bindparam, delete, exists, func, select, text, update
 from sqlalchemy.dialects.postgresql import insert as pg_insert
@@ -301,12 +301,17 @@ def set_progress(db: Session, user: User, video_id: str, position: int) -> None:
 # --- playlists -------------------------------------------------------------------------------
 
 
+# Every reason a move is refused; the UI names each one (`playlists.moveErrors.<reason>`, held by the
+# frontend's backendIds contract, which reads this Literal).
+MoveReason = Literal["same_playlist", "not_in_playlist"]
+
+
 class MoveRefused(Exception):
     """A move between playlists that cannot happen: `reason` is the code the UI translates."""
 
-    def __init__(self, reason: str):
+    def __init__(self, reason: MoveReason):
         super().__init__(reason)
-        self.reason = reason
+        self.reason: MoveReason = reason
 
 
 def touch(pl: Playlist) -> None:

backend/app/refusal.py

@@ -1,29 +1,39 @@
 """A request the app refuses, said in a way the UI can put in the reader's language.
 
 Every refusal the API answers carries a structured `detail` — `{code, reason, …params}` — and the client
-translates it (`lib/api/core.ts` `localizeDetail`). A bare English string reached the Hungarian UI
+translates it (`lib/api/refusalText.ts` `localizeDetail`). A bare English string reached the Hungarian UI
 verbatim: the blocking error dialog, and every inline surface that printed `HttpError.detail`, showed
 whatever sentence the route happened to hand-write. `refused` is the generic family
 (`errors.refused.<reason>`, the params interpolated into the sentence); the older specific codes
 (`not_found`, `youtube`, `playlist`, the admin refusals, …) stay, since each is already translated.
 
-A test (`test_http_details.py`) reads every `HTTPException` in the app and fails on a string detail,
-and the frontend's contract test requires every `refused(…, "<reason>")` to be named in both
-languages — so the rule is enforced, not described.
+A test (`test_http_details.py`) reads every place an `HTTPException` or a `JSONResponse` sends a detail
+and fails on one the client cannot say: a sentence, a dict without a `code`, a variable, none at all.
+`tests/refusal_sites.py` reads every `{"code": …}` detail from the syntax tree, written where it is sent
+(or returned by a factory that only ever is), with any `**` spread before its `code` and `reason`, and
+follows each reason along a closed list of shapes: a literal, a `Literal` type on the parameter or
+attribute it travels in, every call of a helper like `refused` below, a map's values; anything else is
+reported, never guessed. The frontend's contract test
+(`i18n/backendIds.contract.test.ts`) runs it and requires each code in one record of
+`lib/api/refusalCodes.ts`, and each reason's sentence in both languages; a code or reason it cannot
+follow fails it, unless no screen shows that code. So the rule is enforced, not described.
 """
 
 from fastapi import HTTPException
 
+from app.sysconfig import InvalidSetting, SettingReason
+
 
 def refused(status: int, reason: str, **params: object) -> HTTPException:
     """The refusal to raise: `raise refused(409, "view_name_taken", name=name)`. `params` travel in
-    the detail for the sentence to interpolate (`{{name}}`); keep them to values the reader may see."""
-    return HTTPException(status_code=status, detail={"code": "refused", "reason": reason, **params})
+    the detail for the sentence to interpolate (`{{name}}`); keep them to values the reader may see.
+    They are spread first, so a `code` or `reason` among them could never replace these two."""
+    return HTTPException(status_code=status, detail={**params, "code": "refused", "reason": reason})
 
 
-# `sysconfig.InvalidSetting.reason` → the refusal it answers as. A dict of literals, so the frontend's
-# contract test can read every reason this can produce.
-_SETTING_REASONS = {
+# `sysconfig.InvalidSetting.reason` → the refusal it answers as. A dict of literals, so the refusal
+# scan reads every reason this can produce, and holds its keys to `SettingReason`.
+_SETTING_REASONS: dict[SettingReason, str] = {
     "not_a_number": "setting_not_a_number",
     "too_low": "setting_too_low",
     "too_high": "setting_too_high",
@@ -32,6 +42,6 @@ _SETTING_REASONS = {
 }
 
 
-def setting_refused(exc) -> HTTPException:
+def setting_refused(exc: InvalidSetting) -> HTTPException:
     """A value the admin entered that `sysconfig.set_value` refused (`exc`: its `InvalidSetting`)."""
     return refused(400, _SETTING_REASONS[exc.reason], key=exc.key, **exc.params)

backend/app/routes/auth.py

@@ -976,7 +976,16 @@ def _resend_verify_if_eligible(email: str) -> None:
             send_verification_link(db, user)
 
 
-def _login_refused(status: int, reason: str, user: User | None = None, **extra) -> HTTPException:
+# Every refusal a password sign-in answers with; the UI names each one (`welcome.auth.blocked.<reason>`,
+# held by the frontend's backendIds contract, which reads this Literal).
+LoginRefusal = Literal[
+    "rate_limited", "invalid", "suspended", "email_unverified", "pending_approval"
+]
+
+
+def _login_refused(
+    status: int, reason: LoginRefusal, user: User | None = None, **extra
+) -> HTTPException:
     """Every refusal password_login can answer with, in the codebase's structured `{code, reason}`
     shape so the SPA can say it in the user's own language (the old bare English strings were
     unreadable under a bilingual UI, and unusable as anything but a one-line error).
@@ -992,15 +1001,15 @@ def _login_refused(status: int, reason: str, user: User | None = None, **extra)
     `email_verified` is false, and vice versa — the SPA renders whichever is actually outstanding
     rather than assuming a sequence.
     """
-    detail: dict = {"code": "login", "reason": reason}
-    if user is not None:
-        detail |= {
-            "email": user.email,
-            "email_verified": user.email_verified,
-            "approved": user.is_active,
-        }
-    detail |= {k: v for k, v in extra.items() if v is not None}
-    return HTTPException(status_code=status, detail=detail)
+    account = (
+        {"email": user.email, "email_verified": user.email_verified, "approved": user.is_active}
+        if user is not None
+        else {}
+    )
+    given = {k: v for k, v in extra.items() if v is not None}
+    return HTTPException(
+        status_code=status, detail={**account, **given, "code": "login", "reason": reason}
+    )
 
 
 @router.post("/password-login")

backend/app/routes/downloads.py

@@ -208,7 +208,7 @@ def set_credential(
     try:
         cleaned = dlcreds.validate_cookies(body.cookies)
     except dlcreds.InvalidCookies as e:
-        raise HTTPException(status_code=400, detail={"code": "cookies", "reason": str(e)}) from e
+        raise HTTPException(status_code=400, detail={"code": "cookies", "reason": e.reason}) from e
     dlcreds.upsert_credential(db, user.id, host_key, cleaned)
     audit.record(
         db,
@@ -359,8 +359,9 @@ def enqueue_clip(
         job = service.enqueue_clip(db, user.id, spec, display_name=display_name)
     except clipmod.ClipError as e:
         status = 404 if e.reason == "not_found" else 422
-        detail = {"code": "clip", "reason": e.reason, **e.params}
-        raise HTTPException(status_code=status, detail=detail) from e
+        raise HTTPException(
+            status_code=status, detail={**e.params, "code": "clip", "reason": e.reason}
+        ) from e
     except quota.QuotaExceeded as e:
         raise HTTPException(status_code=422, detail=quota_detail(e)) from e
     db.commit()

backend/app/routes/feed.py

@@ -249,6 +249,21 @@ def set_video_progress(
     return {"ok": True, "video_id": video_id, "position_seconds": position}
 
 
+@router.get("/videos/{video_id}/row")
+def get_video_row(
+    video_id: str = Path(max_length=32),
+    user: User = Depends(current_user),
+    db: Session = Depends(get_db),
+) -> dict:
+    """One catalog video as the feed lists it (its channel, this user's watch state and resume point,
+    saved): what a player opened from an address starts from. The catalog only, so it costs nothing;
+    every video a player can open (a list's row, a related one) is in it."""
+    rows = queries.feed_rows_by_ids(db, user, [video_id])
+    if not rows:
+        raise not_found("video")
+    return rows[0]
+
+
 @router.get("/videos/{video_id}")
 def get_video_detail(
     video_id: str,

backend/app/routes/files.py

@@ -139,7 +139,7 @@ def own_job_for_update(db: Session, user: User, job_id: int) -> "DownloadJob":
 
 def quota_detail(e: quota.QuotaExceeded) -> dict:
     """Structured error the trilingual client localizes (reason key + numbers), instead of a
-    pre-baked English string with a dot-decimal GB value. See lib/api.ts localizeDetail()."""
+    pre-baked English string with a dot-decimal GB value. See lib/api/refusalText.ts localizeDetail()."""
     return {"code": "quota", "reason": e.reason, "limit": e.limit, "current": e.current}
 
 

backend/app/routes/playlists.py

@@ -3,7 +3,7 @@ CRUD (create / rename / delete, add / remove / reorder items) plus YouTube two-w
 mirror the user's own YouTube playlists in (`/sync-youtube`) and push/revert local edits back
 out (`/{id}/push-plan`, `/{id}/revert-youtube`), behind the optional write scope."""
 
-from typing import TYPE_CHECKING
+from typing import TYPE_CHECKING, Literal
 
 from fastapi import APIRouter, Depends, HTTPException
 from pydantic import BaseModel, Field
@@ -53,7 +53,22 @@ def _check_pull_cooldown(user: User) -> None:
         raise HTTPException(status_code=429, detail={"code": "sync_cooldown"})
 
 
-def _refused(status: int, reason: str) -> HTTPException:
+# Every playlist action the server refuses; the UI names each one (`playlists.errors.<reason>`, held by
+# the frontend's backendIds contract, which reads this Literal).
+PlaylistRefusal = Literal[
+    "name_required",
+    "not_on_youtube",
+    "quota_exceeded",
+    "sync_all_busy",
+    "sync_busy",
+    "watch_later_not_pushable",
+    "watch_later_undeletable",
+    "youtube_editing_off",
+    "youtube_read_scope",
+]
+
+
+def _refused(status: int, reason: PlaylistRefusal) -> HTTPException:
     """A playlist action the server refuses, as a reason the UI translates
     (`playlists.errors.<reason>`) — a bare English detail reached the Hungarian UI verbatim."""
     return HTTPException(status_code=status, detail={"code": "playlist", "reason": reason})

backend/app/routes/plex/playback.py

@@ -234,6 +234,15 @@ def person_image(u: str, request: Request) -> Response:
     return imgcache.response(data, ct)
 
 
+def _supersede_resume_pushes(user_id: int, item_id: int, now: datetime) -> None:
+    """A watched mark supersedes every resume push still in flight for the item: stamping it as the
+    latest push makes `_resume_push_superseded` drop them. Popping the entry instead (to keep the map
+    small) removed the very guard, and an older resume push could then land at Plex AFTER the
+    scrobble and revive a resume point on a watched item. Eviction bounds the map."""
+    with _push_throttle_lock:
+        _last_push_at[(user_id, item_id)] = now
+
+
 def _push_resume_guarded(
     user_id: int,
     item_id: int,
@@ -329,12 +338,7 @@ def item_progress(
     near_end = duration > 0 and position > duration - _FINISH_MARGIN_S
     if near_end:
         flipped = service.mark_finished(db, user.id, it.id, now)
-        # The finish supersedes every resume push still in flight for this item: stamping it as the
-        # latest push makes `_resume_push_superseded` drop them. Popping the entry instead (to keep
-        # the map small) removed the very guard, and an older resume push could then land at Plex
-        # AFTER the scrobble and revive a resume point on a watched item. Eviction bounds the map.
-        with _push_throttle_lock:
-            _last_push_at[(user.id, it.id)] = now
+        _supersede_resume_pushes(user.id, it.id, now)
         db.commit()
         # Only the checkpoint that flipped the row scrobbles: a later checkpoint of the same finished
         # item — or a second one racing this one — would otherwise bump Plex's viewCount again.
@@ -352,7 +356,11 @@ def item_progress(
     push_now = _should_push_resume(user.id, it.id, now, final)
     # Marked dirty before the (background) push so the reconcile knows to re-push if it fails, and so
     # `push_state_to_plex` can settle synced_to_plex once Plex confirms.
-    service.checkpoint(db, user, it.id, st, position, now, dirty=push_now)
+    if not service.checkpoint(db, user, it.id, st, position, now, dirty=push_now):
+        # Marked watched a moment ago: this is the finishing player's late tick (see
+        # `service.checkpoint`), and the answer is the same one a near-end checkpoint gets.
+        db.commit()
+        return {"ok": True, "status": "watched", "position_seconds": 0}
     db.commit()
     if push_now:
         _push_watch(
@@ -408,6 +416,8 @@ def item_state(
             _push_watch(background, db, user.id, it.id, rating_key, "unwatched")
         return {"ok": True, "status": "new"}
     service.set_status(db, user, it.id, st, status)
+    if status == "watched":
+        _supersede_resume_pushes(user.id, it.id, datetime.now(timezone.utc))
     db.commit()
     if status == "watched" and prev_status != "watched":
         _push_watch(background, db, user.id, it.id, rating_key, "watched")
@@ -427,6 +437,10 @@ def _bulk_state(
     always reads the committed marks."""
     pushable = plex_watch.link_for_push(db, user_id) is not None
     to_push = service.bulk_state(db, user_id, eps, watched)
+    if watched:
+        now = datetime.now(timezone.utc)
+        for item_id, _rating_key, _action in to_push:
+            _supersede_resume_pushes(user_id, item_id, now)
     if pushable and to_push:
         # One coalesced background task for the whole batch (reuses a single session + Plex client),
         # not one task per episode — a 200-ep show mark is 1 task, not 200.
@@ -632,9 +646,10 @@ def stream_hls_file(
     try:
         content = path.read_bytes()
     except OSError:
-        # The session was torn down between the wait and the read — `_kill` rmtrees the whole
-        # directory, and nothing holds `_lock` across those two steps. It has to present as the same
-        # 404 a gone session does: the player's recovery is keyed on the STATUS (`code === 404`), so
+        # The session was torn down between the wait and the read — teardown moves the whole
+        # directory aside and deletes it, and nothing holds `_lock` across those two steps. It has
+        # to present as the same 404 a gone session does: the player's recovery is keyed on the
+        # STATUS (`code === 404`), so
         # a 500 here skipped the reclaim and ended playback with "couldn't play" instead of
         # restarting at the playhead. Ordinary trigger: `loadSession` awaits the new session — which
         # kills and rmtrees the old one — before destroying the old hls instance, so the outgoing

backend/app/routes/saved_views.py

@@ -128,7 +128,8 @@ def update_view(
         db.commit()
     except IntegrityError:
         db.rollback()
-        raise refused(409, "view_name_taken", name=view.name) from None
+        # The name asked for: the rollback has put the view's old name back on `view`.
+        raise refused(409, "view_name_taken", name=name) from None
     return _serialize(view)
 
 

backend/app/routes/tags.py

@@ -107,7 +107,8 @@ def update_tag(
         db.commit()
     except IntegrityError:
         db.rollback()
-        raise refused(409, "tag_name_taken", name=tag.name) from None
+        # The name asked for: the rollback has put the tag's old name back on `tag`.
+        raise refused(409, "tag_name_taken", name=name) from None
     return {
         "ok": True,
         "id": tag.id,

backend/app/sysconfig.py

@@ -443,15 +443,20 @@ def _default(s: ConfigSpec):
     return getattr(settings, s.default_attr)
 
 
+# Every reason `set_value` refuses with. `refusal.setting_refused` looks each one up in its map, which
+# the refusal scan holds to exactly these keys: a reason the map lacks would answer a 500.
+SettingReason = Literal["not_a_number", "too_low", "too_high", "not_a_choice", "no_encryption_key"]
+
+
 class InvalidSetting(ValueError):
     """A value `set_value` refuses, as a reason the UI translates (`errors.refused.setting_<reason>`)
     plus what the sentence needs — the English message is for logs only. A ValueError still, so a
     caller that only needs "refused or not" keeps working."""
 
-    def __init__(self, key: str, reason: str, **params: object):
+    def __init__(self, key: str, reason: SettingReason, **params: object):
         super().__init__(f"{key}: {reason} {params}")
         self.key = key
-        self.reason = reason
+        self.reason: SettingReason = reason
         self.params = params
 
 

backend/requirements.lock

@@ -6,9 +6,10 @@
 # bumped in place instead of a full regeneration, which would move every other package too — then
 # `pip install -r requirements.lock && pip check` must pass. In place so far: urllib3 2.7.0 -> 2.8.0 (PYSEC-2026-4175/4176/4177); yt-dlp 2026.7.4 -> 2026.8.19
 # (it marks the clients that need a stream PO token, so the downloader stops fetching into a 403);
-# certifi 2026.7.22 -> 2026.10.19 (GHSA-6q48-6c7w-9gw2); brotli 1.2.0 -> 1.2.1 (PYSEC-2026-4322).
+# certifi 2026.7.22 -> 2026.10.19 (GHSA-6q48-6c7w-9gw2); brotli 1.2.0 -> 1.2.1 (PYSEC-2026-4322);
+# Authlib 1.7.2 -> 1.9.1 (CVE-2026-96760, CVE-2026-114616); joserfc 1.7.4 -> 1.7.6 (CVE-2026-119283, CVE-2026-119284).
 APScheduler==3.11.3
-Authlib==1.7.2
+Authlib==1.9.1
 Mako==1.4.1
 MarkupSafe==3.0.3
 PyYAML==6.0.3
@@ -38,7 +39,7 @@ httptools==0.8.0
 httpx==0.28.1
 idna==3.18
 itsdangerous==2.2.0
-joserfc==1.7.4
+joserfc==1.7.6
 markdown-it-py==4.2.0
 mdurl==0.1.2
 mutagen==1.48.1

backend/tests/refusal_sites.py

@@ -0,0 +1,738 @@
+"""Every refusal the backend can answer, read from its syntax tree: each `{"code": …, "reason": …}` detail,
+with every reason its code can be sent with.
+
+The frontend's contract (`i18n/backendIds.contract.test.ts`) runs this and requires a sentence for each
+code and reason in both languages. A scan that tries to follow every shape opens a silent gap with each one
+it learns, and following how a value flows through Python (variables, scopes, aliases, a dict changed in
+place) never closes. So the CODE keeps to a narrow form, and this reads a CLOSED list of it, reporting
+everything else, never guessing:
+
+- where a detail stands: where it is sent — `HTTPException`'s second argument or `detail=`, the `"detail"`
+  value of a `JSONResponse`'s content dict — through the arms of `a if c else b`, or as what a module-level
+  factory returns when every return of it is a detail and every reference to it is a call sent as one. A
+  detail held in a variable is not followed;
+- the code: one literal. A `**` spread, or a key that is not a literal, stands BEFORE a literal `code` and
+  `reason`, both of which the detail then carries: the later key wins, so no spread can change them;
+- a reason: a string literal (`None` sends none: the site counts as reasonless); both arms of
+  `a if c else b`; a function's local bound only by plain `x = …`; a module constant reached as `mod.NAME`;
+  a call's `Literal` return annotation;
+- a parameter typed with a `Literal` (basedpyright holds every value passed in), or a `str` one of a
+  module-level helper (`refused`, `not_found`), followed to every call, each of which must pass it by
+  position or by name; a parameter its body binds again is unread;
+- an attribute: `e.x` of the exception an `except C as e` catches, or of a parameter typed `C`, when a
+  method of `C` declares `self.x: <Literal>`;
+- a map lookup (`_SETTING_REASONS[exc.reason]`): the map's values, and its keys must be exactly what the
+  index can be.
+
+A name bound twice at module level, inside a module-level `if`/`try`/loop, named by a `global`, or imported
+from two places is not looked up; nor is a local a lambda or a comprehension binds, or one a `nonlocal` or
+`global` names. A module constant or map that anything stores into, deletes from or (a map) uses but by
+`map[k]` or a read method is unread. A reference named like a followed helper that the scan cannot resolve
+(`import app.x`, a relative import, an app module that does not bind it) is unread. Anything else is UNREAD,
+or an unread code, and the contract fails on it unless no screen shows that code. Stdlib only: it runs on
+the host, beside the frontend's tests (`python -I backend/tests/refusal_sites.py` → JSON).
+"""
+
+import ast
+import json
+import pathlib
+import sys
+from collections.abc import Iterator
+from dataclasses import dataclass, field
+
+APP = pathlib.Path(__file__).resolve().parents[1] / "app"
+
+# Files whose `"code"` dicts are data, not refusals: a subtitle track's status payload, TMDB country codes.
+NOT_REFUSALS = {
+    "plex/subtitles.py": "a subtitle track's status payload (its own `code`)",
+    "plex/tmdb.py": "a production country's ISO code",
+}
+
+# What a map may be used by besides `map[k]`: a method that only reads it.
+READS = {"get", "items", "keys", "values"}
+
+Node = ast.AST
+FUNCS = (ast.FunctionDef, ast.AsyncFunctionDef)
+SCOPES = (ast.FunctionDef, ast.AsyncFunctionDef, ast.Lambda, ast.ClassDef)
+COMPREHENSIONS = (ast.ListComp, ast.SetComp, ast.DictComp, ast.GeneratorExp)
+COMPOUND = (
+    ast.If,
+    ast.Try,
+    ast.TryStar,
+    ast.For,
+    ast.AsyncFor,
+    ast.While,
+    ast.With,
+    ast.AsyncWith,
+    ast.Match,
+)
+
+
+@dataclass
+class Res:
+    values: set[str] = field(default_factory=set)
+    unread: list[str] = field(default_factory=list)
+    none: bool = False  # an arm sends no reason
+
+    def __or__(self, other: "Res") -> "Res":
+        return Res(self.values | other.values, self.unread + other.unread, self.none or other.none)
+
+
+@dataclass
+class Module:
+    path: str  # relative to app/, posix
+    name: str  # dotted, `app.…`
+    tree: ast.Module
+    parents: dict[Node, Node]
+    # local name → (module, symbol or None for the module)
+    imports: dict[str, tuple[str, str | None]]
+    top: dict[str, Node]  # module-level bindings: def, class, or the assignment
+    ambiguous: set[
+        str
+    ]  # bound more than once, conditionally, by a `global`, or imported from two places
+    slots: set[int]  # the ids of the nodes sent as a detail
+
+
+def _own_scope(node: Node) -> Iterator[Node]:
+    """`node` and what it holds in its own scope: a nested def, class or lambda is itself, not its body."""
+    stack = [node]
+    while stack:
+        n = stack.pop()
+        yield n
+        if n is not node and isinstance(n, SCOPES):
+            continue
+        stack.extend(ast.iter_child_nodes(n))
+
+
+def _stored(target: Node) -> set[str]:
+    """The names an assignment target binds, not the ones it reads (`LABELS[k] = v` binds none)."""
+    return {
+        n.id for n in ast.walk(target) if isinstance(n, ast.Name) and isinstance(n.ctx, ast.Store)
+    }
+
+
+def _binds(node: Node) -> set[str]:
+    """The names one node binds in the scope it sits in."""
+    if isinstance(node, ast.Assign):
+        return set().union(*(_stored(t) for t in node.targets))
+    if isinstance(node, (ast.AnnAssign, ast.AugAssign, ast.For, ast.AsyncFor, ast.NamedExpr)):
+        return _stored(node.target)
+    if isinstance(node, (ast.With, ast.AsyncWith)):
+        return set().union(*(_stored(i.optional_vars) for i in node.items if i.optional_vars))
+    if isinstance(node, (ast.Import, ast.ImportFrom)):
+        return {(a.asname or a.name).split(".")[0] for a in node.names}
+    if isinstance(node, (ast.FunctionDef, ast.AsyncFunctionDef, ast.ClassDef)):
+        return {node.name}
+    if isinstance(node, (ast.MatchAs, ast.MatchStar, ast.ExceptHandler)) and node.name:
+        return {node.name}
+    return set()
+
+
+def _sender(call: ast.Call) -> str | None:
+    return getattr(call.func, "id", None) or getattr(call.func, "attr", None)
+
+
+def detail_slots(tree: Node) -> Iterator[tuple[ast.Call, Node | None]]:
+    """Every place a detail is sent from, with what it holds: `HTTPException`'s second argument or
+    `detail=` (None: sent without one), and the `"detail"` value of a `JSONResponse`'s content dict (a
+    content without one is an answer, not a refusal)."""
+    for node in ast.walk(tree):
+        if not isinstance(node, ast.Call):
+            continue
+        kw = {k.arg: k.value for k in node.keywords}
+        if _sender(node) == "HTTPException":
+            yield node, kw.get("detail", node.args[1] if len(node.args) > 1 else None)
+        elif _sender(node) == "JSONResponse":
+            content = kw.get("content", node.args[0] if node.args else None)
+            if isinstance(content, ast.Dict):
+                for k, v in zip(content.keys, content.values, strict=True):
+                    if isinstance(k, ast.Constant) and k.value == "detail":
+                        yield node, v
+
+
+def _code_dict(node: Node) -> bool:
+    """A `{"code": …}` dict, or a `dict(code=…)` call."""
+    if isinstance(node, ast.Dict):
+        return any(isinstance(k, ast.Constant) and k.value == "code" for k in node.keys)
+    return (
+        isinstance(node, ast.Call)
+        and getattr(node.func, "id", None) == "dict"
+        and any(k.arg == "code" for k in node.keywords)
+    )
+
+
+def _module_name(path: str) -> str:
+    parts = path.removesuffix(".py").split("/")
+    if parts[-1] == "__init__":
+        parts = parts[:-1]
+    return ".".join(["app", *parts])
+
+
+def _load(sources: dict[str, str]) -> dict[str, Module]:
+    mods: dict[str, Module] = {}
+    for path, src in sources.items():
+        tree = ast.parse(src)
+        parents = {child: node for node in ast.walk(tree) for child in ast.iter_child_nodes(node)}
+        origins: dict[str, set[tuple[str, str | None]]] = {}
+        ambiguous: set[str] = set()
+        for node in ast.walk(tree):
+            if isinstance(node, ast.ImportFrom) and node.module and node.level == 0:
+                for a in node.names:
+                    origins.setdefault(a.asname or a.name, set()).add((node.module, a.name))
+            elif isinstance(node, ast.Import):
+                for a in node.names:
+                    if a.asname:
+                        origins.setdefault(a.asname, set()).add((a.name, None))
+            elif isinstance(node, ast.Global):
+                ambiguous |= set(node.names)
+        top: dict[str, Node] = {}
+        count: dict[str, int] = {}
+        ambiguous |= {name for name, o in origins.items() if len(o) > 1}
+        for stmt in tree.body:
+            if isinstance(stmt, (ast.FunctionDef, ast.AsyncFunctionDef, ast.ClassDef)):
+                top[stmt.name] = stmt
+            elif isinstance(stmt, ast.Assign):
+                for t in stmt.targets:
+                    if isinstance(t, ast.Name):
+                        top[t.id] = stmt
+            elif isinstance(stmt, ast.AnnAssign) and isinstance(stmt.target, ast.Name):
+                top[stmt.target.id] = stmt
+            for n in [stmt] if isinstance(stmt, SCOPES) else _own_scope(stmt):
+                for name in _binds(n):
+                    count[name] = count.get(name, 0) + 1
+                    if isinstance(stmt, COMPOUND):
+                        ambiguous.add(name)
+        ambiguous |= {name for name, c in count.items() if c > 1}
+        imports = {name: next(iter(o)) for name, o in origins.items() if name not in ambiguous}
+        slots = {id(d) for _, d in detail_slots(tree) if d is not None}
+        name = _module_name(path)
+        mods[name] = Module(path, name, tree, parents, imports, top, ambiguous, slots)
+    return mods
+
+
+class Scan:
+    def __init__(self, sources: dict[str, str]):
+        self.mods = _load(sources)
+        self.errors: list[str] = []
+        self._following: set[tuple[str, str, str]] = set()
+        self._followed: dict[tuple[str, str, str], Res] = {}
+        self._resolving: set[int] = set()
+        self._factory: dict[int, bool] = {}
+        self._changed: dict[int, bool] = {}
+
+    # --- names ---------------------------------------------------------------------------------------
+
+    def lookup(
+        self, m: Module, name: str, seen: frozenset[tuple[str, str]] = frozenset()
+    ) -> tuple[Module, Node] | tuple[str, None] | None:
+        """What a module-level name is: (its module, its binding), or (a module's name, None)."""
+        if name in m.ambiguous:
+            return None
+        if name in m.top:
+            return m, m.top[name]
+        if name in m.imports:
+            mod, sym = m.imports[name]
+            if sym is None:
+                return (mod, None) if mod in self.mods else None
+            if f"{mod}.{sym}" in self.mods:
+                return f"{mod}.{sym}", None
+            if mod in self.mods and (mod, sym) not in seen:
+                return self.lookup(self.mods[mod], sym, seen | {(mod, sym)})
+        return None
+
+    def lookup_expr(self, m: Module, e: Node) -> tuple[Module, Node] | tuple[str, None] | None:
+        if isinstance(e, ast.Name):
+            return None if self.binder(m, e) is not None else self.lookup(m, e.id)
+        if isinstance(e, ast.Attribute):
+            base = self.lookup_expr(m, e.value)
+            if base and base[1] is None and isinstance(base[0], str):
+                return self.lookup(self.mods[base[0]], e.attr)
+        return None
+
+    def binder(self, m: Module, e: ast.Name) -> Node | None:
+        """The innermost scope `e` is bound in: a function (a parameter, or a binding in its own body), a
+        lambda (a parameter), a comprehension (its target); None: a module-level name."""
+        node = m.parents.get(e)
+        while node is not None:
+            if isinstance(node, (*FUNCS, ast.Lambda)):
+                a = node.args
+                params = [*a.posonlyargs, *a.args, *a.kwonlyargs, a.vararg, a.kwarg]
+                if e.id in {p.arg for p in params if p}:
+                    return node
+                if isinstance(node, FUNCS) and self.assignments(node, e.id):
+                    return node
+            elif isinstance(node, COMPREHENSIONS) and any(
+                e.id in _stored(g.target) for g in node.generators
+            ):
+                return node
+            node = m.parents.get(node)
+        return None
+
+    def at(self, m: Module, e: Node) -> str:
+        return f"{m.path}:{getattr(e, 'lineno', '?')}: {ast.unparse(e)}"
+
+    def enclosing(self, m: Module, e: Node, kind: type | tuple[type, ...]) -> Node | None:
+        node = m.parents.get(e)
+        while node is not None and not isinstance(node, kind):
+            node = m.parents.get(node)
+        return node
+
+    def assignments(self, fn: Node, name: str) -> list[Node]:
+        """What binds `name` in this function's own body (not in a nested one)."""
+        return [n for n in _own_scope(fn) if n is not fn and name in _binds(n)]
+
+    def caught_as(self, m: Module, e: Node, name: str) -> ast.ExceptHandler | None:
+        node = m.parents.get(e)
+        while node is not None and not isinstance(node, FUNCS):
+            if isinstance(node, ast.ExceptHandler) and node.name == name:
+                return node
+            node = m.parents.get(node)
+        return None
+
+    def references(
+        self, m: Module, target: Node
+    ) -> Iterator[tuple[Module, Node, ast.Call | None, bool]]:
+        """Every reference to a module-level def or class: the call it makes (None: not a call), and
+        whether it resolved. A reference named like it that the scan cannot resolve is yielded too."""
+        name = getattr(target, "name", None)
+        for cm in self.mods.values():
+            for node in ast.walk(cm.tree):
+                if not isinstance(node, (ast.Name, ast.Attribute)) or not isinstance(
+                    node.ctx, ast.Load
+                ):
+                    continue
+                if (node.id if isinstance(node, ast.Name) else node.attr) != name:
+                    continue
+                parent = cm.parents.get(node)
+                if isinstance(parent, ast.Attribute) and parent.value is node:
+                    continue
+                found = self.lookup_expr(cm, node)
+                if found:
+                    if not (found[0] is m and found[1] is target):
+                        continue
+                elif not self.unresolved(cm, node):
+                    continue
+                call = parent if isinstance(parent, ast.Call) and parent.func is node else None
+                yield cm, node, call, found is not None
+
+    def unresolved(self, m: Module, node: Node) -> bool:
+        """A name, or a dotted path, the app could mean that the scan cannot resolve: not a local, nor an
+        outside module's (an attribute of an object the function holds is not one)."""
+        root = node
+        while isinstance(root, ast.Attribute):
+            root = root.value
+        if not isinstance(root, ast.Name) or self.binder(m, root) is not None:
+            return False
+        if root.id in m.ambiguous or (root.id not in m.top and root.id not in m.imports):
+            return True
+        if root.id in m.top:
+            return False
+        if root is node:  # imported from an app module that does not bind it where the scan can see
+            mod = m.imports[root.id][0]
+            return (mod == "app" or mod.startswith("app.")) and self.lookup(m, root.id) is None
+        found = self.lookup(m, root.id)
+        return (
+            found is not None and found[1] is None
+        )  # an app module whose dotted path went nowhere
+
+    def changed(self, m: Module, stmt: Node, name: str, *, only_read: bool) -> bool:
+        """Something in the app stores into, deletes or rebinds the module-level `name` that `stmt` binds,
+        or (`only_read`, a map) uses it but by `map[k]` or a method that only reads it."""
+        key = id(stmt) * 2 + only_read
+        if key in self._changed:
+            return self._changed[key]
+        own = stmt.targets if isinstance(stmt, ast.Assign) else [getattr(stmt, "target", None)]
+        out = False
+        for cm in self.mods.values():
+            for node in ast.walk(cm.tree):
+                if out:
+                    break
+                if not (
+                    isinstance(node, ast.Name)
+                    and node.id == name
+                    or isinstance(node, ast.Attribute)
+                    and node.attr == name
+                ) or (cm is m and node in own):
+                    continue
+                found = self.lookup_expr(cm, node)
+                if not (found and found[0] is m and found[1] is stmt):
+                    continue
+                if not isinstance(node.ctx, ast.Load):
+                    out = True
+                elif only_read:
+                    p = cm.parents.get(node)
+                    out = not (
+                        isinstance(p, ast.Subscript)
+                        and p.value is node
+                        and isinstance(p.ctx, ast.Load)
+                        or isinstance(p, ast.Attribute)
+                        and p.attr in READS
+                    )
+        self._changed[key] = out
+        return out
+
+    # --- types ---------------------------------------------------------------------------------------
+
+    def ann_values(self, m: Module, ann: Node | None, depth: int = 0) -> set[str] | None:
+        """The values a `Literal[…]` annotation, or an alias of one, allows; None when it is not one."""
+        if isinstance(ann, ast.Subscript) and getattr(ann.value, "id", None) == "Literal":
+            items = ann.slice.elts if isinstance(ann.slice, ast.Tuple) else [ann.slice]
+            if all(isinstance(i, ast.Constant) and isinstance(i.value, str) for i in items):
+                return {i.value for i in items}
+            return None
+        if isinstance(ann, (ast.Name, ast.Attribute)) and depth < 8:
+            found = self.lookup_expr(m, ann)
+            if found and isinstance(found[0], Module) and isinstance(found[1], ast.Assign):
+                return self.ann_values(found[0], found[1].value, depth + 1)
+        return None
+
+    def classes(self, m: Module, e: Node | None) -> list[tuple[Module, ast.ClassDef]] | None:
+        found = self.lookup_expr(m, e) if e is not None else None
+        if found and isinstance(found[0], Module) and isinstance(found[1], ast.ClassDef):
+            return [(found[0], found[1])]
+        return None
+
+    def typed(self, m: Module, at: Node, name: str) -> list[tuple[Module, ast.ClassDef]] | None:
+        """The class `name` holds where `at` sits: the one an `except C as name` catches, or a parameter's
+        annotation (a parameter its body binds again holds no known class)."""
+        handler = self.caught_as(m, at, name)
+        if handler is not None:
+            return self.classes(m, handler.type)
+        fn = self.enclosing(m, at, FUNCS)
+        if fn is None:
+            return None
+        params = {a.arg: a for a in [*fn.args.posonlyargs, *fn.args.args, *fn.args.kwonlyargs]}
+        if name in params and not self.assignments(fn, name):
+            return self.classes(m, params[name].annotation)
+        return None
+
+    def attr_values(self, cm: Module, cls: ast.ClassDef, attr: str) -> set[str] | None:
+        """An attribute's `Literal` values, from `self.attr: T` in a method of the class."""
+        for node in ast.walk(cls):
+            if (
+                isinstance(node, ast.AnnAssign)
+                and isinstance(node.target, ast.Attribute)
+                and node.target.attr == attr
+                and getattr(node.target.value, "id", None) == "self"
+            ):
+                return self.ann_values(cm, node.annotation)
+        return None
+
+    # --- reasons -------------------------------------------------------------------------------------
+
+    def resolve(self, m: Module, e: Node) -> Res:
+        if isinstance(e, ast.Constant):
+            if e.value is None:
+                return Res(none=True)
+            if isinstance(e.value, str):
+                return Res({e.value})
+        if isinstance(e, ast.IfExp):
+            return self.resolve(m, e.body) | self.resolve(m, e.orelse)
+        if isinstance(e, ast.Name):
+            return self.resolve_name(m, e)
+        if isinstance(e, ast.Attribute):
+            return self.resolve_attr(m, e)
+        if isinstance(e, ast.Call):
+            found = self.lookup_expr(m, e.func)
+            if found and isinstance(found[0], Module) and isinstance(found[1], FUNCS):
+                v = self.ann_values(found[0], found[1].returns)
+                if v is not None:
+                    return Res(v)
+        if isinstance(e, ast.Subscript):
+            return self.resolve_lookup(m, e)
+        return Res(unread=[self.at(m, e)])
+
+    def resolve_name(self, m: Module, e: ast.Name) -> Res:
+        if self.caught_as(m, e, e.id) is not None:
+            return Res(unread=[self.at(m, e)])  # the exception itself, not a reason
+        fn = self.binder(m, e)
+        if fn is None:
+            return Res(unread=[self.at(m, e)])
+        if not isinstance(fn, FUNCS):
+            return Res(unread=[f"{self.at(m, e)} (bound by a lambda or a comprehension)"])
+        if any(isinstance(n, (ast.Nonlocal, ast.Global)) and e.id in n.names for n in ast.walk(fn)):
+            return Res(unread=[f"{self.at(m, e)} (named by a nonlocal or a global)"])
+        a = fn.args
+        params = {p.arg: p for p in [*a.posonlyargs, *a.args, *a.kwonlyargs]}
+        assigned = self.assignments(fn, e.id)
+        if e.id in params:
+            if assigned:
+                return Res(unread=[f"{self.at(m, e)} (a parameter its body binds again)"])
+            return self.resolve_param(m, fn, params[e.id], e)
+        out = Res(unread=[] if assigned else [self.at(m, e)])  # `*args`, `**kwargs`
+        for s in assigned:
+            if not (isinstance(s, ast.Assign) and all(isinstance(t, ast.Name) for t in s.targets)):
+                out = out | Res(unread=[self.at(m, e)])
+            elif id(s) in self._resolving:
+                out = out | Res(unread=[f"{self.at(m, e)} (reached again while it is resolved)"])
+            else:
+                self._resolving.add(id(s))
+                out = out | self.resolve(m, s.value)
+                self._resolving.discard(id(s))
+        return out
+
+    def resolve_param(self, m: Module, fn: Node, param: ast.arg, e: Node) -> Res:
+        v = self.ann_values(m, param.annotation)
+        if v is not None:
+            return Res(v)
+        if param.annotation is not None and getattr(param.annotation, "id", None) != "str":
+            return Res(unread=[self.at(m, e)])
+        return self.follow(m, fn, param)
+
+    def follow(self, m: Module, fn: Node, param: ast.arg) -> Res:
+        """A `str` parameter of a helper: what every call of the helper passes it."""
+        assert isinstance(fn, FUNCS)
+        key = (m.name, fn.name, param.arg)
+        if key in self._followed:
+            return self._followed[key]
+        where = f"{m.path}:{fn.lineno}: {fn.name}({param.arg})"
+        if key in self._following:
+            return Res(unread=[f"{where} reached again while it is followed"])
+        if m.top.get(fn.name) is not fn or fn.name in m.ambiguous:
+            return Res(unread=[f"{where} is not a module-level helper"])
+        self._following.add(key)
+        positional = [a.arg for a in [*fn.args.posonlyargs, *fn.args.args]]
+        by_name = param not in fn.args.posonlyargs
+        out = Res()
+        for cm, node, call, resolved in self.references(m, fn):
+            if not resolved:
+                out = out | Res(
+                    unread=[f"{self.at(cm, node)} (a reference the scan cannot resolve)"]
+                )
+                continue
+            if call is None:
+                out = out | Res(unread=[f"{self.at(cm, node)} (the helper used as a value)"])
+                continue
+            kw = {k.arg: k.value for k in call.keywords}
+            given = param.arg in positional and positional.index(param.arg) < len(call.args)
+            if by_name and param.arg in kw:
+                out = out | self.resolve(cm, kw[param.arg])
+            elif any(isinstance(a, ast.Starred) for a in call.args):
+                out = out | Res(unread=[self.at(cm, call)])
+            elif given:
+                out = out | self.resolve(cm, call.args[positional.index(param.arg)])
+            else:
+                out = out | Res(unread=[f"{self.at(cm, call)} (does not pass {param.arg})"])
+        self._followed[key] = out  # once followed, its key answers from here: never reached again
+        return out
+
+    def resolve_attr(self, m: Module, e: ast.Attribute) -> Res:
+        base = e.value
+        if isinstance(base, ast.Name):
+            typed = self.typed(m, e, base.id)
+            if typed is not None:
+                out = Res()
+                for cm, cls in typed:
+                    v = self.attr_values(cm, cls, e.attr)
+                    out = out | (
+                        Res(v)
+                        if v is not None
+                        else Res(
+                            unread=[f"{self.at(m, e)} ({cls.name}.{e.attr} has no Literal type)"]
+                        )
+                    )
+                return out
+        found = self.lookup_expr(m, e)
+        if (
+            found
+            and isinstance(found[0], Module)
+            and isinstance(found[1], (ast.Assign, ast.AnnAssign))
+            and isinstance(found[1].value, ast.Constant)
+        ):
+            if self.changed(found[0], found[1], e.attr, only_read=False):
+                return Res(unread=[f"{self.at(m, e)} (bound again or deleted elsewhere)"])
+            return self.resolve(found[0], found[1].value)
+        return Res(unread=[self.at(m, e)])
+
+    def resolve_lookup(self, m: Module, e: ast.Subscript) -> Res:
+        found = self.lookup_expr(m, e.value)
+        if not (
+            found
+            and isinstance(found[0], Module)
+            and isinstance(found[1], (ast.Assign, ast.AnnAssign))
+        ):
+            return Res(unread=[self.at(m, e)])
+        table = found[1].value
+        if not isinstance(table, ast.Dict) or not all(
+            isinstance(k, ast.Constant) and isinstance(k.value, str) for k in table.keys
+        ):
+            return Res(unread=[self.at(m, e)])
+        name = e.value.attr if isinstance(e.value, ast.Attribute) else getattr(e.value, "id", "")
+        if self.changed(found[0], found[1], name, only_read=True):
+            return Res(unread=[f"{self.at(m, e)} (the map is changed after it is built)"])
+        out = Res()
+        for v in table.values:
+            out = out | self.resolve(found[0], v)
+        index = self.resolve(m, e.slice)
+        keys = {k.value for k in table.keys if isinstance(k, ast.Constant)}
+        if index.unread or index.none or index.values != keys:
+            self.errors.append(
+                f"{self.at(m, e)}: the map's keys {sorted(keys)} are not what its index can be "
+                f"{sorted(index.values)}{' + unread ' + str(index.unread) if index.unread else ''}"
+            )
+        return out
+
+    # --- sites ---------------------------------------------------------------------------------------
+
+    def is_detail(self, node: Node | None) -> bool:
+        if isinstance(node, ast.IfExp):
+            return self.is_detail(node.body) and self.is_detail(node.orelse)
+        return _code_dict(node)
+
+    def factory(self, m: Module, fn: Node) -> bool:
+        """A module-level function each return of which is a detail, and each reference to which is a
+        call sent as one (`quota_detail`)."""
+        assert isinstance(fn, FUNCS)
+        if id(fn) in self._factory:
+            return self._factory[id(fn)]
+        returns = [n for n in _own_scope(fn) if isinstance(n, ast.Return)]
+        ok = (
+            m.top.get(fn.name) is fn  # a name bound twice: its calls are unresolved below
+            and bool(returns)
+            and all(self.is_detail(r.value) for r in returns)
+        )
+        for cm, _, call, resolved in self.references(m, fn) if ok else []:
+            ok = resolved and id(call) in cm.slots  # a bare reference is no call: never sent
+            if not ok:
+                break
+        self._factory[id(fn)] = ok
+        return ok
+
+    def placed(self, m: Module, d: Node) -> bool:
+        """`d` is sent as a detail: from a sender's slot, through the arms of `a if c else b`, or as what a
+        factory returns."""
+        holder, p = d, m.parents.get(d)
+        while isinstance(p, ast.IfExp) and holder is not p.test:
+            holder, p = p, m.parents.get(p)
+        if id(holder) in m.slots:
+            return True
+        fn = self.enclosing(m, p, FUNCS) if isinstance(p, ast.Return) else None
+        return fn is not None and self.factory(m, fn)
+
+    def sayable(self, m: Module, d: Node | None) -> bool:
+        """What a slot holds is a detail the client can say: a code dict, or a factory's call."""
+        if isinstance(d, ast.IfExp):
+            return self.sayable(m, d.body) and self.sayable(m, d.orelse)
+        if _code_dict(d):
+            return True
+        found = self.lookup_expr(m, d.func) if isinstance(d, ast.Call) else None
+        return bool(
+            found
+            and isinstance(found[0], Module)
+            and isinstance(found[1], FUNCS)
+            and self.factory(found[0], found[1])
+        )
+
+    def entries(self, d: Node) -> list[tuple[str | None, Node]]:
+        """A dict's (key, value) pairs: None for a `**` spread, "?" for a key that is not a literal."""
+        if isinstance(d, ast.Dict):
+            return [
+                (
+                    k.value
+                    if isinstance(k, ast.Constant) and isinstance(k.value, str)
+                    else None
+                    if k is None
+                    else "?",
+                    v,
+                )
+                for k, v in zip(d.keys, d.values, strict=True)
+            ]
+        assert isinstance(d, ast.Call)
+        return [(None, a) for a in d.args] + [(k.arg, k.value) for k in d.keywords]
+
+    def site(self, m: Module, d: Node, out: dict) -> None:
+        items = self.entries(d)
+        code = Res()
+        for v in (v for k, v in items if k == "code"):
+            code = code | self.resolve(m, v)
+        problems = [
+            f"{self.at(m, v)} (a spread in dict())"
+            for k, v in items
+            if k is None and isinstance(d, ast.Call)
+        ] + [
+            f"{self.at(m, v)} (a spread or a computed key the code and the reason do not follow)"
+            for i, (k, v) in enumerate(items)
+            if k in (None, "?") and not {"code", "reason"} <= {k2 for k2, _ in items[i + 1 :]}
+        ]
+        if not self.placed(m, d):
+            problems.append(f"{self.at(m, d)} (a detail put where the scan cannot follow it)")
+        if code.unread or code.none or len(code.values) != 1 or problems:
+            out["unreadCodes"] += problems or [self.at(m, d)]
+            return
+        entry = out["codes"].setdefault(
+            next(iter(code.values)), {"reasons": set(), "unread": [], "sites": 0, "reasonless": []}
+        )
+        entry["sites"] += 1
+        res, has_reason = Res(), False
+        for k, v in items:
+            if k == "reason":
+                res, has_reason = res | self.resolve(m, v), True
+        if not has_reason or res.none:
+            entry["reasonless"].append(f"{m.path}:{d.lineno}")
+        entry["reasons"] |= res.values
+        entry["unread"] += res.unread
+
+    def other_details(self) -> list[tuple[str, int, str | None]]:
+        """Each slot that sends what the client cannot say — nothing, or anything but a code dict or a
+        factory's call: (its file, its line, the function it is sent from)."""
+        out = []
+        for m in self.mods.values():
+            for call, d in detail_slots(m.tree):
+                if self.sayable(m, d):
+                    continue
+                fn = self.enclosing(m, call, FUNCS)
+                out.append((m.path, call.lineno, getattr(fn, "name", None)))
+        return sorted(out)
+
+    def run(self) -> dict:
+        out: dict = {
+            "codes": {},
+            "unreadCodes": [],
+            "errors": self.errors,
+            "excluded": {},
+            "aliases": {},
+            "notRefusals": sorted(NOT_REFUSALS),
+        }
+        for m in self.mods.values():
+            for name, stmt in m.top.items():
+                if (
+                    isinstance(stmt, ast.Assign)
+                    and isinstance(stmt.value, ast.Subscript)
+                    and (v := self.ann_values(m, stmt.value))
+                ):
+                    out["aliases"].setdefault(m.path, {})[name] = sorted(v)
+            for node in ast.walk(m.tree):
+                if not _code_dict(node):
+                    continue
+                if m.path in NOT_REFUSALS:
+                    out["excluded"][m.path] = out["excluded"].get(m.path, 0) + 1
+                    continue
+                self.site(m, node, out)
+        for entry in out["codes"].values():
+            entry["reasons"] = sorted(entry["reasons"])
+        return out
+
+
+def scan(sources: dict[str, str]) -> dict:
+    return Scan(sources).run()
+
+
+def app_sources(app: pathlib.Path = APP) -> dict[str, str]:
+    return {
+        p.relative_to(app).as_posix(): p.read_text(encoding="utf-8")
+        for p in sorted(app.rglob("*.py"))
+        if "__pycache__" not in p.parts
+    }
+
+
+def scan_app(app: pathlib.Path = APP) -> dict:
+    return scan(app_sources(app))
+
+
+if __name__ == "__main__":
+    json.dump(
+        scan_app(pathlib.Path(sys.argv[1]) if len(sys.argv) > 1 else APP),
+        sys.stdout,
+        indent=1,
+        sort_keys=True,
+    )

backend/tests/test_hls_reaper.py

@@ -83,6 +83,7 @@ class _Proc:
 
 class _Session:
     def __init__(self, tmp_path, name: str, finished: bool, idle_s: float):
+        self.key = name
         self.dir = tmp_path / name
         self.dir.mkdir()
         self.proc = _Proc(finished)

backend/tests/test_hls_teardown.py

@@ -0,0 +1,158 @@
+"""Tearing a session down does not stall everybody else's playback.
+
+Every segment request (`current_session`) and every checkpoint (`touch_session`) takes the one
+registry `_lock`. Stopping a session waits up to 3 s for its ffmpeg to exit and then deletes a whole
+segmented film, ~1200 files — and that used to happen under the same lock, so one viewer's seek, a
+cap cull or a reap pass held up every other viewer's HLS requests for seconds, each one a parked
+threadpool worker and its pooled DB connection.
+
+What still has to be atomic is pinned too: a session directory is reused for the same item, offset
+and tag, so a new session on that path must not start before the old ffmpeg — which writes by path
+— has exited.
+"""
+
+import threading
+import time
+
+import pytest
+
+from app.plex import stream
+
+
+class _SlowProc:
+    """An ffmpeg that takes a while to exit after TERM: `wait` blocks until `exited` is set."""
+
+    def __init__(self, order: list[str], name: str):
+        self.order = order
+        self.name = name
+        self.waiting = threading.Event()
+        self.exited = threading.Event()
+
+    def poll(self):
+        return 0 if self.exited.is_set() else None
+
+    def terminate(self):
+        pass
+
+    def kill(self):
+        self.exited.set()
+
+    def wait(self, timeout=None):
+        self.waiting.set()
+        if not self.exited.wait(timeout):
+            raise stream.subprocess.TimeoutExpired("ffmpeg", timeout)
+        self.order.append(f"{self.name} exited")
+        return 0
+
+
+class _Session:
+    def __init__(self, directory, proc, key: str):
+        self.id = f"sid-{key}"
+        self.key = key
+        self.dir = directory
+        self.proc = proc
+        self.last_access = time.time()
+        self.transcode = False
+
+
+@pytest.fixture
+def sessions(monkeypatch):
+    live: dict = {}
+    monkeypatch.setattr(stream, "_sessions", live)
+    monkeypatch.setattr(stream, "_dying", {}, raising=False)
+    return live
+
+
+def test_stopping_a_session_does_not_hold_up_another_viewers_requests(tmp_path, sessions):
+    order: list[str] = []
+    slow = _SlowProc(order, "a")
+    d = tmp_path / "1_u1_0_0_+0.00"
+    d.mkdir()
+    (d / "seg_0.ts").write_bytes(b"x")
+    sessions[(1, "a")] = _Session(d, slow, "a")
+    sessions[(2, "b")] = _Session(tmp_path / "2_u2_0_0_+0.00", _SlowProc(order, "b"), "b")
+
+    stopper = threading.Thread(target=stream.stop_session, args=(1, "a", "sid-a"))
+    stopper.start()
+    try:
+        assert slow.waiting.wait(2.0), "the stop never waited for its ffmpeg"
+        got: list = []
+        reader = threading.Thread(target=lambda: got.append(stream.current_session(2, "b")))
+        reader.start()
+        reader.join(1.0)
+        assert not reader.is_alive(), "a segment request waited on another viewer's teardown"
+        assert got and got[0] is sessions[(2, "b")]
+    finally:
+        slow.exited.set()
+        stopper.join(5.0)
+    # The teardown still finishes: the session is gone and nothing of its directory is left behind.
+    assert (1, "a") not in sessions
+    assert sorted(p.name for p in tmp_path.iterdir()) == []
+
+
+def test_a_reap_pass_does_not_hold_up_another_viewers_requests(tmp_path, sessions):
+    order: list[str] = []
+    slow = _SlowProc(order, "a")
+    d = tmp_path / "1_u1_0_0_+0.00"
+    d.mkdir()
+    gone = _Session(d, slow, "a")
+    gone.last_access = time.time() - stream._SESSION_IDLE_S - 5
+    sessions[(1, "a")] = gone
+    sessions[(2, "b")] = _Session(tmp_path / "2_u2_0_0_+0.00", _SlowProc(order, "b"), "b")
+
+    reaper = threading.Thread(target=stream.reap_idle)
+    reaper.start()
+    try:
+        assert slow.waiting.wait(2.0), "the reap never waited for its ffmpeg"
+        toucher = threading.Thread(target=stream.touch_session, args=(2, "b"))
+        toucher.start()
+        toucher.join(1.0)
+        assert not toucher.is_alive(), "a checkpoint waited on another viewer's teardown"
+    finally:
+        slow.exited.set()
+        reaper.join(5.0)
+    assert list(sessions) == [(2, "b")]
+    assert not d.exists()
+
+
+class _FakeItem:
+    rating_key = "12345"
+    file_path = "/media/movie.mkv"
+    playable = "remux"
+    codec_video = "h264"
+
+
+def test_a_new_session_on_a_dying_ones_path_starts_only_after_it_exited(
+    tmp_path, sessions, monkeypatch
+):
+    """The same item at the same second gets the same directory. The old ffmpeg writes by PATH, so
+    while it is still winding down after TERM it can write a segment — or, on a clean exit, a final
+    playlist with ENDLIST — into the NEW session's directory."""
+    order: list[str] = []
+    procs = iter([_SlowProc(order, "old"), _SlowProc(order, "new")])
+
+    def popen(*a, **k):
+        order.append("popen")
+        return next(procs)
+
+    monkeypatch.setattr(stream, "_HLS_ROOT", tmp_path)
+    src = tmp_path / "movie.mkv"
+    src.write_bytes(b"x")
+    monkeypatch.setattr(stream.paths, "local_media_path", lambda db, fp: src)
+    monkeypatch.setattr(stream.sysconfig, "get_int", lambda db, k: 2)
+    monkeypatch.setattr(stream.sysconfig, "get_bool", lambda db, k: False)
+    monkeypatch.setattr(stream.subprocess, "Popen", popen)
+    monkeypatch.setattr(stream, "wait_for", lambda *a, **k: True)
+
+    first = stream.start_session(db=None, user_id=7, item=_FakeItem(), start_s=0.0)
+    assert first is not None
+    stopper = threading.Thread(target=stream.stop_session, args=(7, "12345", first.id))
+    stopper.start()
+    assert first.proc.waiting.wait(2.0)
+    threading.Timer(0.3, first.proc.exited.set).start()
+    second = stream.start_session(db=None, user_id=7, item=_FakeItem(), start_s=0.0)
+    stopper.join(5.0)
+    assert second is not None and second.dir == first.dir
+    assert order.index("old exited") < order.index("popen", 1)
+    assert second.dir.is_dir(), "the old teardown deleted the new session's directory"
+    second.proc.exited.set()

backend/tests/test_http_details.py

@@ -1,53 +1,88 @@
-"""No refusal answers in a hand-written English sentence.
+"""No refusal answers in a way the client cannot say.
 
 The UI is bilingual and translates a structured `detail` (`{code, reason, …}`), but a string detail it
 can only print as it came — so ~150 of them reached the Hungarian UI verbatim, in the blocking error
 dialog and on every inline surface that shows `HttpError.detail`. `app/refusal.py` is the family they
-became; this test is what keeps a new one from being written the old way. Pure: it reads the sources.
+became; this test is what keeps a new one from being written the old way. It reads the same slots the
+refusal scan does (`refusal_sites.detail_slots`), so the two cannot disagree on where a detail is sent.
+Pure: it reads the sources.
 """
 
-import ast
-import pathlib
+import textwrap
 
-APP = pathlib.Path(__file__).resolve().parents[1] / "app"
+from tests.refusal_sites import Scan, app_sources
+
+# Answers that are no refusal of the app's, by the function they are sent from: the client shows a
+# detail only when it is an object (`lib/api/core.ts`), so these read as its generic line, and no screen
+# needs more from them.
+NO_REFUSAL = {
+    ("main.py", "setup_gate"): "the 503 before setup: the setup screen is what the user sees",
+    ("main.py", "spa_fallback"): "a bare 404 for an api path no route matches: no screen calls one",
+    ("main.py", "_validation_error"): "FastAPI's own 422 list: a body the client itself got wrong",
+    ("routes/diagnostics.py", "_parsed_events"): "the client-events beacon's 422: nothing shows it",
+}
 
 
-def _is_text(node: ast.AST) -> bool:
-    """A detail that is a sentence: a literal, an f-string, `str(exc)`, or `"…" + x`."""
-    if isinstance(node, ast.Constant) and isinstance(node.value, str):
-        return True
-    if isinstance(node, ast.JoinedStr):
-        return True
-    if isinstance(node, ast.Call) and getattr(node.func, "id", "") == "str":
-        return True
-    if isinstance(node, ast.BoolOp):
-        return any(_is_text(v) for v in node.values)
-    if isinstance(node, ast.BinOp):
-        return _is_text(node.left) or _is_text(node.right)
-    return False
+def _offenders(sources: dict[str, str]) -> list[str]:
+    return [
+        f"{path}:{line}"
+        for path, line, fn in Scan(sources).other_details()
+        if (path, fn) not in NO_REFUSAL
+    ]
 
 
-def test_no_http_exception_carries_a_sentence():
-    offenders = []
-    for path in sorted(APP.rglob("*.py")):
-        for node in ast.walk(ast.parse(path.read_text(encoding="utf-8"))):
-            if not (
-                isinstance(node, ast.Call)
-                and getattr(node.func, "id", getattr(node.func, "attr", "")) == "HTTPException"
-            ):
-                continue
-            kw = {k.arg: k.value for k in node.keywords}
-            detail = kw.get("detail", node.args[1] if len(node.args) > 1 else None)
-            if detail is not None and _is_text(detail):
-                offenders.append(f"{path.relative_to(APP).as_posix()}:{node.lineno}")
+def test_every_detail_is_one_the_client_can_say():
+    offenders = _offenders(app_sources())
     assert offenders == [], (
-        "a refusal with an English sentence for a detail — raise `refused(status, reason)` "
-        f"(app/refusal.py) and name the reason in both locales: {offenders}"
+        "a refusal the client can only answer with its generic line — send `{code, reason}` "
+        f"(`refused(status, reason)`), or list it in NO_REFUSAL with why: {offenders}"
     )
 
 
-def test_the_scan_sees_a_sentence_when_there_is_one():
+def test_the_detail_scan_sees_each_shape_the_client_cannot_say():
     """A guard that matches nothing is green over nothing."""
-    sample = ast.parse('HTTPException(status_code=400, detail=f"bad {x}")').body[0].value
-    assert _is_text(sample.keywords[1].value)
-    assert not _is_text(ast.parse('{"code": "refused", "reason": "x"}').body[0].value)
+    src = textwrap.dedent(
+        """
+        def f(x):
+            raise HTTPException(409, detail={"reason": "view_name_taken"})
+        def g(x):
+            raise HTTPException(409, dict(reason="taken"))
+        def h(x):
+            raise HTTPException(status_code=404)
+        def i(x):
+            return JSONResponse({"detail": "This instance isn't set up yet."}, status_code=503)
+        def j(x):
+            return JSONResponse(content={"detail": {"reason": "x"}}, status_code=409)
+        def k(x):
+            raise HTTPException(400, detail=f"bad {x}")
+        def l(x):
+            raise HTTPException(404, None)
+        def n(x, msg):
+            raise HTTPException(400, detail=msg)
+        def o(x):
+            raise HTTPException(400, detail=["a sentence"])
+        def p(x):
+            raise HTTPException(400, detail=describe(x))
+        def q(x):
+            raise HTTPException(400, detail={"code": "a"} if x else "text")
+        def r(x):
+            raise HTTPException(400, detail=nothing(x))
+        def nothing(x):
+            pass
+        def ok(x):
+            raise HTTPException(409, {"code": "refused", "reason": "x"})
+            raise HTTPException(409, detail=quota(x))
+            raise HTTPException(409, detail={"code": "a"} if x else {"code": "b"})
+            return JSONResponse({"detail": {"code": "too_large"}}, status_code=413)
+            return JSONResponse({"ok": True})
+        def quota(x):
+            return {"code": "quota", "reason": "files"}
+        def setup_gate(x):
+            return JSONResponse({"detail": "listed"}, status_code=503)
+        """
+    )
+    lines = (3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25)
+    assert _offenders({"main.py": src}) == [f"main.py:{n}" for n in lines]
+    # A file whose code dicts are data still answers its refusals in a way the client can say.
+    data = 'def f():\n    raise HTTPException(400, "text")\n'
+    assert _offenders({"plex/tmdb.py": data}) == ["plex/tmdb.py:2"]

backend/tests/test_name_taken_detail.py

@@ -0,0 +1,46 @@
+"""A rename onto a name already taken says WHICH name is taken: the one asked for, not the row's
+old name (the rollback that follows the conflict puts the old name back on the row). DB lane.
+"""
+
+from fastapi.testclient import TestClient
+
+import app.state as state
+from app.auth import current_user
+from app.db import get_db
+from app.main import app
+from app.models import User
+
+
+def _client(db, monkeypatch, override_dep):
+    u = User(email="taken@example.com")
+    db.add(u)
+    db.commit()
+    monkeypatch.setattr(
+        state, "_configured_cache", True
+    )  # the request gate 503s an unconfigured app
+    override_dep(get_db, db.info["request"])
+    override_dep(current_user, lambda: u)
+    return TestClient(app)
+
+
+def test_renaming_a_view_onto_a_taken_name_names_the_taken_one(db, monkeypatch, override_dep):
+    c = _client(db, monkeypatch, override_dep)
+    gaming = c.post("/api/saved-views", json={"name": "gaming", "filters": {}, "source": "feed"})
+    assert gaming.status_code == 200
+    hh = c.post("/api/saved-views", json={"name": "hh", "filters": {}, "source": "feed"}).json()
+
+    r = c.patch(f"/api/saved-views/{hh['id']}", json={"name": "gaming"})
+
+    assert r.status_code == 409
+    assert r.json()["detail"] == {"code": "refused", "reason": "view_name_taken", "name": "gaming"}
+
+
+def test_renaming_a_tag_onto_a_taken_name_names_the_taken_one(db, monkeypatch, override_dep):
+    c = _client(db, monkeypatch, override_dep)
+    assert c.post("/api/tags", json={"name": "music"}).status_code == 200
+    news = c.post("/api/tags", json={"name": "news"}).json()
+
+    r = c.patch(f"/api/tags/{news['id']}", json={"name": "music"})
+
+    assert r.status_code == 409
+    assert r.json()["detail"] == {"code": "refused", "reason": "tag_name_taken", "name": "music"}

backend/tests/test_plex_finish.py

@@ -13,7 +13,7 @@ from datetime import datetime, timedelta, timezone
 from sqlalchemy import select
 
 from app.db import SessionLocal
-from app.plex.models import PlexItem, PlexLibrary, PlexState
+from app.plex.models import PlexItem, PlexLibrary, PlexSeason, PlexShow, PlexState
 from app.plex import service as plex_service
 from app.routes.plex import playback
 
@@ -81,3 +81,150 @@ def test_the_finish_supersedes_a_resume_push_still_in_flight(db, as_user, make_u
     )
     assert r.json() == {"ok": True, "status": "watched", "position_seconds": 0}
     assert playback._resume_push_superseded(user.id, item.id, earlier) is True
+
+
+def test_a_checkpoint_sent_before_the_finish_does_not_land_on_the_watched_row(
+    db, as_user, make_user, monkeypatch
+):
+    """The 10 s tick posted at 2699 of 3000 s (not near the end) races the credits auto-skip's
+    "watched". When the mark commits first, the late checkpoint used to write its position onto the
+    watched row and schedule a resume push after the scrobble: Plex showed the item in progress, and
+    a Plex-authoritative pull imported it back."""
+    user = make_user()
+    item = _item(db)
+    monkeypatch.setattr(playback.plex_stream, "touch_session", lambda uid, key: None)
+    client = as_user(user)
+    assert client.post("/api/plex/item/m1/state", json={"status": "watched"}).status_code == 200
+
+    r = client.post(
+        "/api/plex/item/m1/progress", json={"position_seconds": 2699, "duration_seconds": 3000}
+    )
+    assert r.status_code == 200, r.text
+    assert r.json() == {"ok": True, "status": "watched", "position_seconds": 0}
+    db.expire_all()
+    st = db.execute(select(PlexState).where(PlexState.item_id == item.id)).scalars().one()
+    assert (st.status, st.position_seconds) == ("watched", 0)
+
+
+def test_a_rewatch_records_its_position_once_the_finish_is_behind_it(
+    db, as_user, make_user, monkeypatch
+):
+    """The other half: a watched item played again is still checkpointed — only a position arriving
+    right on the heels of the mark is read as that mark's late tick."""
+    user = make_user()
+    item = _item(db)
+    long_ago = datetime.now(timezone.utc) - timedelta(days=3)
+    db.add(PlexState(user_id=user.id, item_id=item.id, status="watched", watched_at=long_ago))
+    db.commit()
+    monkeypatch.setattr(playback.plex_stream, "touch_session", lambda uid, key: None)
+    r = as_user(user).post(
+        "/api/plex/item/m1/progress", json={"position_seconds": 600, "duration_seconds": 3000}
+    )
+    assert r.json() == {"ok": True, "position_seconds": 600}
+    db.expire_all()
+    st = db.execute(select(PlexState).where(PlexState.item_id == item.id)).scalars().one()
+    assert (st.status, st.position_seconds) == ("watched", 600)
+
+
+def test_marking_watched_supersedes_a_resume_push_still_in_flight(
+    db, as_user, make_user, monkeypatch
+):
+    """The same guard the near-end finish has: a resume push scheduled before the mark must not reach
+    Plex after its scrobble."""
+    user = make_user()
+    item = _item(db)
+    earlier = datetime.now(timezone.utc) - timedelta(seconds=5)
+    assert playback._should_push_resume(user.id, item.id, earlier, final=True)
+    r = as_user(user).post("/api/plex/item/m1/state", json={"status": "watched"})
+    assert r.status_code == 200, r.text
+    assert playback._resume_push_superseded(user.id, item.id, earlier) is True
+
+
+def _state(db, user, item):
+    db.expire_all()
+    st = (
+        db.execute(
+            select(PlexState).where(PlexState.user_id == user.id, PlexState.item_id == item.id)
+        )
+        .scalars()
+        .one()
+    )
+    return st.status, st.position_seconds
+
+
+def test_a_mark_committed_after_the_checkpoints_read_still_refuses_it(db, make_user):
+    """The race itself, not its sequential shadow: the route read the row while it was still in
+    progress, and the finish committed from another session before the checkpoint wrote. Only a write
+    conditional on the row as it is NOW refuses that position."""
+    user = make_user()
+    item = _item(db)
+    db.add(PlexState(user_id=user.id, item_id=item.id, status="new", position_seconds=2690))
+    db.commit()
+    now = datetime.now(timezone.utc)
+    read = plex_service.state_row(db, user, item.id)  # what the checkpoint's route read: "new"
+    assert read.status == "new"
+
+    other = SessionLocal()
+    try:
+        assert plex_service.mark_finished(other, user.id, item.id, now) is True
+        other.commit()
+    finally:
+        other.close()
+
+    assert plex_service.checkpoint(db, user, item.id, read, 2699, now, dirty=True) is False
+    db.commit()
+    assert _state(db, user, item) == ("watched", 0)
+
+
+def test_a_tick_seconds_behind_the_mark_is_refused_a_rewatch_a_minute_later_is_not(db, make_user):
+    """A position right behind the mark is that mark's late tick; one a minute later is a rewatch.
+    Literal times on purpose: a window widened to an hour must fail here, not move with it."""
+    user = make_user()
+    item = _item(db)
+    now = datetime.now(timezone.utc)
+    st = PlexState(user_id=user.id, item_id=item.id, status="watched", watched_at=now)
+    db.add(st)
+    db.commit()
+
+    st.watched_at = now - timedelta(seconds=20)
+    db.commit()
+    assert plex_service.checkpoint(db, user, item.id, st, 600, now, dirty=True) is False
+    db.commit()
+    st.watched_at = now - timedelta(seconds=60)
+    db.commit()
+    assert plex_service.checkpoint(db, user, item.id, st, 600, now, dirty=True) is True
+    db.commit()
+    assert _state(db, user, item) == ("watched", 600)
+
+
+def test_marking_a_season_watched_supersedes_its_episodes_resume_pushes(db, as_user, make_user):
+    """The bulk mark has the same guard as one item's: an episode's resume push scheduled before
+    the season was marked must not reach Plex after the scrobble."""
+    user = make_user()
+    lib = PlexLibrary(plex_key="2", title="Shows", kind="show", enabled=True)
+    db.add(lib)
+    db.flush()
+    sh = PlexShow(rating_key="sh1", library_id=lib.id, title="Show")
+    db.add(sh)
+    db.flush()
+    se = PlexSeason(rating_key="se1", show_id=sh.id, season_number=1)
+    db.add(se)
+    db.flush()
+    ep = PlexItem(
+        rating_key="e1",
+        library_id=lib.id,
+        kind="episode",
+        title="E1",
+        show_id=sh.id,
+        season_id=se.id,
+        season_number=1,
+        episode_number=1,
+    )
+    db.add(ep)
+    db.commit()
+    earlier = datetime.now(timezone.utc) - timedelta(seconds=5)
+    assert playback._should_push_resume(user.id, ep.id, earlier, final=True)
+
+    r = as_user(user).post("/api/plex/season/se1/state", json={"watched": True})
+    assert r.json() == {"ok": True, "changed": 1, "watched": True}
+    assert playback._resume_push_superseded(user.id, ep.id, earlier) is True

backend/tests/test_plex_hls_file_route.py

@@ -198,6 +198,31 @@ def test_a_name_the_session_cannot_produce_fails_at_once(client, tmp_path, sessi
     assert elapsed < 2.0, f"waited {elapsed:.1f}s for a playlist this session never writes"
 
 
+@pytest.mark.parametrize(
+    ("name", "audio_langs"),
+    [
+        ("seg_00.ts", None),  # `int()` reads it as segment 0, which needs no predecessor
+        ("seg_007.ts", None),  # …as segment 7, whose predecessor seg_6.ts is on disk
+        ("seg_٧.ts", None),  # an Arabic-Indic 7: `\d` and `int()` both take it
+        ("seg_a0_07.ts", ["hu", "en"]),
+        ("seg_0_00.ts", ["hu", "en"]),
+    ],
+)
+def test_a_segment_name_ffmpeg_never_spells_is_refused(tmp_path, name, audio_langs):
+    """ffmpeg writes `seg_%d.ts`: no padding, ASCII digits. A name that only PARSES to a sequence the
+    session has reached is still a file that will never appear, and saying yes to it parked the
+    request for the full 20 s wait — the parking this guard exists to end."""
+    d = tmp_path / "m1_0_0_+0.00"
+    d.mkdir()
+    for v in plex_stream.session_variants(audio_langs) or (None,):
+        (d / plex_stream.segment_name(6, v)).write_bytes(b"x")
+    sess = _Session("sid-a", d, running=True, audio_langs=audio_langs)
+    assert not plex_stream.artifact_may_arrive(sess, name)
+    # The canonical spelling of the same next segment is still accepted.
+    v = (plex_stream.session_variants(audio_langs) or (None,))[0]
+    assert plex_stream.artifact_may_arrive(sess, plex_stream.segment_name(7, v))
+
+
 @pytest.mark.parametrize("digits", [100, 5000])
 def test_an_absurd_segment_index_is_a_404_not_a_500(client, tmp_path, sessions, digits):
     """`int()` on an unbounded digit run raises ValueError past 4300 digits, and only OSError was
@@ -213,7 +238,7 @@ def test_an_absurd_segment_index_is_a_404_not_a_500(client, tmp_path, sessions,
 def test_a_session_torn_down_during_the_read_is_a_404_not_a_500(
     client, monkeypatch, tmp_path, sessions
 ):
-    """`_kill` rmtrees the whole directory and nothing holds `_lock` across the wait and the read,
+    """Teardown moves the whole directory aside and nothing holds `_lock` across the wait and the read,
     so the file can vanish in between — on every seek-restart, since `loadSession` awaits the new
     session before destroying the old hls instance. The player's recovery is keyed on the 404
     STATUS, so a 500 here skipped the reclaim and ended playback with "couldn't play"."""

backend/tests/test_plex_service.py

@@ -348,7 +348,8 @@ def test_an_early_checkpoint_drops_a_bare_state_and_zeroes_a_marked_one(db, make
     user = make_user()
     lib = _lib(db)
     bare, hid = _movie(db, lib, "bare"), _movie(db, lib, "hid")
-    st = service.checkpoint(db, user, bare.id, None, 120, NOW, dirty=True)
+    assert service.checkpoint(db, user, bare.id, None, 120, NOW, dirty=True)
+    st = queries.state(db, user, bare.id)
     assert (st.position_seconds, st.synced_to_plex) == (120, False)
     _state(db, user, hid, status="hidden", position_seconds=40)
     service.clear_progress(db, queries.state(db, user, bare.id), NOW)
@@ -429,7 +430,8 @@ def test_a_first_write_that_lost_the_race_updates_the_winners_row(db, make_user)
     user = make_user()
     it = _movie(db, _lib(db), "m-race")
     _state(db, user, it, position_seconds=10)  # the request that won, committed
-    st = service.checkpoint(db, user, it.id, None, 42, NOW, dirty=True)  # read "none" before it
+    assert service.checkpoint(db, user, it.id, None, 42, NOW, dirty=True)  # read "none" before it
+    st = queries.state(db, user, it.id)
     assert (st.position_seconds, st.synced_to_plex) == (42, False)
     st = service.set_status(db, user, it.id, None, "hidden")
     assert st.status == "hidden"

backend/tests/test_plex_session_stop.py

@@ -39,6 +39,7 @@ class _Proc:
 class _Session:
     def __init__(self, session_id: str, directory):
         self.id = session_id
+        self.key = "m1"
         self.dir = directory
         self.proc = _Proc()
         self.last_access = time.time()

backend/tests/test_plex_stream.py

@@ -26,6 +26,9 @@ from app.plex.stream import _SESSION_DIR_RE
         "12345_0_2_+0.00",  # current shape, explicit audio_ord
         "12345_842_multi_-1.25",  # multi-audio, negative offset
         "12345_842_multi_+12.50",
+        # a torn-down session's directory, moved aside to be deleted outside the lock — left behind
+        # only if the process died between the rename and the delete
+        "12345_u7_842_multi_+12.50.dead-0123abcd",
     ],
 )
 def test_our_session_directories_are_swept(name):
@@ -47,6 +50,9 @@ def test_our_session_directories_are_swept(name):
         "snapshot_2024_backup_+1.00",  # session-ish tail, but the key isn't a rating_key
         "backup_2024_multi_+0.00",
         ".config",
+        "12345_u7_0_0_+0.00.dead-",  # a tombstone suffix with no id
+        "12345_u7_0_0_+0.00.dead-notours!",
+        "backup_u7_0_0_+0.00.dead-0123abcd",
     ],
 )
 def test_foreign_directories_are_left_alone(name):
@@ -159,7 +165,7 @@ class TestSweepOrphans:
 
 
 class _FakeProc:
-    """Stand-in for the ffmpeg Popen — start_session only stores it (and _kill/reap poll it later)."""
+    """Stand-in for the ffmpeg Popen — start_session only stores it (and teardown/reap poll it later)."""
 
     def poll(self):
         return None
@@ -1052,3 +1058,63 @@ class TestSessionsPerViewer:
             self._start(monkeypatch, user_id=uid)
         assert len(stream._sessions) == 3 and (1, "12345") not in stream._sessions
         assert oldest.proc.killed and not oldest.transcode
+
+
+class TestTeardownFinishes:
+    """A session taken down by a cap or replaced by its own viewer is only renamed aside under the
+    lock; it is deleted after. The rename alone already moves the directory and `terminate()` alone
+    already marks the proc killed — so what is pinned here is the tomb: a whole segmented copy of the
+    film that only a restart's sweep would otherwise reclaim."""
+
+    capturing_env = TestTranscodeStartSession.capturing_env
+
+    @staticmethod
+    def _left_behind(root):
+        return sorted(p.name for p in root.iterdir() if stream._TOMB in p.name) + sorted(
+            str(p) for p in stream._dying
+        )
+
+    def test_a_culled_session_is_deleted_not_only_moved_aside(self, capturing_env, monkeypatch):
+        monkeypatch.setattr(stream, "_dying", {})
+        first = TestSessionsPerViewer._start(monkeypatch, user_id=1, rating_key="1")
+        first.last_access -= 60
+        TestSessionsPerViewer._start(monkeypatch, user_id=1, rating_key="2")
+        TestSessionsPerViewer._start(monkeypatch, user_id=1, rating_key="3")
+        assert first.proc.killed and not first.dir.exists()
+        assert self._left_behind(capturing_env) == []
+
+    def test_a_viewers_restart_deletes_the_session_it_replaces(self, capturing_env, monkeypatch):
+        monkeypatch.setattr(stream, "_dying", {})
+        monkeypatch.setattr(
+            stream, "_select_encode", lambda db, item, transcode, src: (False, False)
+        )
+        monkeypatch.setattr(
+            stream, "_probe_first_pts", lambda seg: None
+        )  # no real segment to probe
+        old = stream.start_session(db=None, user_id=1, item=_FakeItem(), start_s=0.0)
+        new = stream.start_session(db=None, user_id=1, item=_FakeItem(), start_s=600.0)
+        assert old.proc.killed and new.dir.exists() and not old.dir.exists()
+        assert self._left_behind(capturing_env) == []
+
+    def test_a_restart_that_fails_to_start_still_deletes_what_it_replaced(
+        self, capturing_env, monkeypatch
+    ):
+        # The new ffmpeg cannot start (a full disk, no ffmpeg, no memory): the old session is already
+        # moved aside, and nothing else in this process would ever delete it.
+        monkeypatch.setattr(stream, "_dying", {})
+        monkeypatch.setattr(
+            stream, "_select_encode", lambda db, item, transcode, src: (False, False)
+        )
+        monkeypatch.setattr(
+            stream, "_probe_first_pts", lambda seg: None
+        )  # no real segment to probe
+        old = stream.start_session(db=None, user_id=1, item=_FakeItem(), start_s=0.0)
+
+        def no_ffmpeg(*args, **kwargs):
+            raise OSError(28, "No space left on device")
+
+        monkeypatch.setattr(stream.subprocess, "Popen", no_ffmpeg)
+        with pytest.raises(OSError):
+            stream.start_session(db=None, user_id=1, item=_FakeItem(), start_s=600.0)
+        assert old.proc.killed and not old.dir.exists()
+        assert self._left_behind(capturing_env) == []

backend/tests/test_refusal_sites.py

@@ -0,0 +1,770 @@
+"""The refusal scan (`refusal_sites.py`) on small sources: each shape on its closed list is followed to its
+values, and each exit from that list is reported, unread or as an unread code. A scan that silently drops a
+shape is a guard green over nothing, so every exit is pinned here, not only the paths the app takes. Pure:
+no app import, no database."""
+
+import textwrap
+
+from tests.refusal_sites import scan, scan_app
+
+
+def _scan(**files: str) -> dict:
+    return scan(
+        {f"{name.replace('__', '/')}.py": textwrap.dedent(src) for name, src in files.items()}
+    )
+
+
+def _code(result: dict, code: str) -> dict:
+    return result["codes"][code]
+
+
+def _unread(result: dict, code: str) -> list[str]:
+    return [u.split(": ", 1)[1] for u in _code(result, code)["unread"]]
+
+
+REFUSAL = """
+    from fastapi import HTTPException
+
+    def refused(status: int, reason: str, **params: object) -> HTTPException:
+        return HTTPException(status_code=status, detail={**params, "code": "refused", "reason": reason})
+"""
+
+
+def test_a_literal_wherever_it_sits_in_the_dict():
+    r = _scan(
+        a="""
+        def f(x):
+            raise HTTPException(409, {"code": "clip", "limit_s": 5, "reason": "too_long"})
+        def g(x):
+            raise HTTPException(409, {"reason": "before", "code": "clip"})
+        def h(x):
+            raise HTTPException(409, {
+                "code": "clip",  # a comment between
+                "reason": "after_comment",
+            })
+        def i(x):
+            raise HTTPException(409, detail=dict(code="clip", reason="by_call"))
+        """
+    )
+    assert _code(r, "clip")["reasons"] == ["after_comment", "before", "by_call", "too_long"]
+    assert _code(r, "clip")["unread"] == []
+
+
+def test_both_arms_of_a_conditional_and_a_none_arm_makes_the_site_reasonless():
+    r = _scan(
+        a="""
+        def f(x):
+            raise HTTPException(409, {"code": "edit", "reason": "a" if x else "b"})
+        def g(x):
+            raise HTTPException(409, {"code": "playlist", "reason": "lit" if x else None})
+        def h(x):
+            raise HTTPException(409, {"code": "busy", "reason": None})
+        """
+    )
+    assert _code(r, "edit")["reasons"] == ["a", "b"] and _code(r, "edit")["reasonless"] == []
+    assert _code(r, "playlist")["reasons"] == ["lit"]
+    assert _code(r, "playlist")["reasonless"] == ["a.py:5"]
+    assert _code(r, "busy")["reasonless"] == ["a.py:7"]
+
+
+def test_what_the_list_does_not_hold_is_unread():
+    r = _scan(
+        a="""
+        def f(x, svc):
+            raise HTTPException(409, {"code": "edit", "reason": x.why or "c"})
+        def g(svc):
+            raise HTTPException(409, {"code": "edit", "reason": svc.reason()})
+        def h():
+            raise HTTPException(409, {"code": "edit", "reason": 5})
+        def i(e):
+            raise HTTPException(409, {"code": "edit", "reason": f"x{e}"})
+        """
+    )
+    assert _unread(r, "edit") == ["x.why or 'c'", "svc.reason()", "5", "f'x{e}'"]
+    assert _code(r, "edit")["reasons"] == []
+
+
+def test_a_helper_is_followed_to_every_call_however_it_is_written():
+    r = _scan(
+        refusal=REFUSAL,
+        routes__a="""
+        from http import HTTPStatus
+        from app import refusal
+        from app.refusal import refused
+
+        def f(status):
+            raise refused(status, "by_name_status")
+        def g():
+            raise refused(HTTPStatus.CONFLICT, reason="by_keyword")
+        def h():
+            raise refusal.refused(409, "qualified")
+        def i(x):
+            raise refused(409, "a" if x else "second_arm")
+        """,
+        routes__b="""
+        from other.lib import refused
+
+        def f():
+            refused("an outside library's, not the app's")
+        """,
+    )
+    assert _code(r, "refused")["reasons"] == [
+        "a",
+        "by_keyword",
+        "by_name_status",
+        "qualified",
+        "second_arm",
+    ]
+    assert _code(r, "refused")["unread"] == []
+
+
+def test_a_call_the_helper_cannot_be_followed_through_is_unread():
+    r = _scan(
+        refusal=REFUSAL,
+        routes__a="""
+        from app.refusal import refused
+
+        def f(args, kw):
+            pick = refused
+            raise refused(*args)
+        def g(kw):
+            raise refused(409, **kw)
+        def h():
+            raise refused(409)
+        """,
+        routes__b="""
+        import app.refusal
+
+        def f():
+            raise app.refusal.refused(409, "dotted")
+        """,
+        routes__c="""
+        from ..refusal import refused
+
+        def f():
+            raise refused(409, "relative")
+        """,
+    )
+    unread = _unread(r, "refused")
+    assert len(unread) == 6
+    assert sum("the helper used as a value" in u for u in unread) == 1
+    assert sum("a reference the scan cannot resolve" in u for u in unread) == 2
+    assert sum("does not pass reason" in u for u in unread) == 2  # `**kw`, and nothing at all
+    assert any(u == "refused(*args)" for u in unread)
+    assert _code(r, "refused")["reasons"] == []
+
+
+def test_a_default_is_not_followed_a_call_must_pass_the_reason():
+    r = _scan(
+        routes___common="""
+        def not_found(what: str = "generic"):
+            return HTTPException(404, {"code": "not_found", "reason": what})
+
+        def get_or_404(db, id_, *, what: str = "generic"):
+            raise not_found(what)
+        """,
+        routes__a="""
+        from app.routes._common import get_or_404, not_found
+
+        def f(db):
+            get_or_404(db, 1, what="user")
+            get_or_404(db, 2)
+            raise not_found("debug_session")
+        def g():
+            raise not_found()
+        """,
+    )
+    assert _code(r, "not_found")["reasons"] == ["debug_session", "user"]
+    assert [u.endswith("(does not pass what)") for u in _unread(r, "not_found")] == [True, True]
+
+
+def test_a_positional_only_reason_passed_by_name_is_not_bound_to_it():
+    r = _scan(
+        a="""
+        def deny(reason: str, /, **params):
+            return HTTPException(409, {"code": "playlist", "reason": reason})
+
+        def f():
+            raise deny("by_position")
+        def g():
+            raise deny(reason="lands_in_params")
+        """
+    )
+    assert _code(r, "playlist")["reasons"] == ["by_position"]
+    assert _unread(r, "playlist") == ["deny(reason='lands_in_params') (does not pass reason)"]
+
+
+def test_a_helper_reaching_two_sites_gives_both_its_reasons_and_one_reached_again_is_unread():
+    r = _scan(
+        a="""
+        def deny(reason: str, admin):
+            if admin:
+                return HTTPException(409, {"code": "activate", "reason": reason})
+            return HTTPException(409, {"code": "playlist", "reason": reason})
+
+        def again(reason: str, n):
+            if n:
+                return again(reason, n - 1)
+            return HTTPException(409, {"code": "edit", "reason": reason})
+
+        def f():
+            raise deny("foo", True)
+        def g():
+            raise again("bar", 3)
+        """
+    )
+    assert _code(r, "activate")["reasons"] == ["foo"]
+    assert _code(r, "playlist")["reasons"] == ["foo"]
+    assert _code(r, "edit")["reasons"] == ["bar"]
+    assert any("reached again while it is followed" in u for u in _unread(r, "edit"))
+
+
+def test_a_parameter_its_body_binds_again_is_unread():
+    r = _scan(
+        a="""
+        from typing import Literal
+
+        def refused(status, reason: str = ""):
+            reason = reason or "fallback"
+            return HTTPException(status, {"code": "refused", "reason": reason})
+
+        def typed(reason: Literal["a"]):
+            if not reason:
+                reason = "b"
+            return HTTPException(409, {"code": "edit", "reason": reason})
+
+        def f():
+            raise refused(409, "x")
+        """
+    )
+    assert _code(r, "refused")["reasons"] == []
+    assert _unread(r, "refused") == ["reason (a parameter its body binds again)"]
+    assert _unread(r, "edit") == ["reason (a parameter its body binds again)"]
+
+
+def test_a_local_is_followed_only_through_plain_assignments():
+    r = _scan(
+        a="""
+        from typing import Literal
+
+        def f(x):
+            why = "first"
+            if x:
+                why = "second" if x > 1 else "third"
+            raise HTTPException(409, {"code": "edit", "reason": why})
+        def g(svc):
+            hit, why = svc.fetch()
+            raise HTTPException(409, {"code": "playlist", "reason": why})
+        def h(items):
+            for why in items:
+                pass
+            raise HTTPException(409, {"code": "playlist", "reason": why})
+        def i():
+            why: Literal["typed"] = pick()
+            raise HTTPException(409, {"code": "playlist", "reason": why})
+        def j(items):
+            LABELS[why] = "NotAReason"
+            raise HTTPException(409, {"code": "playlist", "reason": why})
+        def k(*why):
+            raise HTTPException(409, {"code": "playlist", "reason": why})
+        """
+    )
+    assert _code(r, "edit")["reasons"] == ["first", "second", "third"]
+    assert _code(r, "playlist")["reasons"] == []
+    assert _unread(r, "playlist") == [
+        "why",
+        "why",
+        "why",
+        "why",
+        "why",
+    ]  # unpacked, a loop, annotated, unbound, `*args`
+
+
+def test_a_call_answers_with_its_literal_return_type():
+    r = _scan(
+        a="""
+        from typing import Literal
+
+        def why(x) -> Literal["quota", "gone"]:
+            return "quota"
+        def how(x) -> str:
+            return "x"
+
+        def f(x):
+            raise HTTPException(409, {"code": "youtube", "reason": why(x)})
+        def g(x):
+            raise HTTPException(409, {"code": "youtube", "reason": how(x)})
+        """
+    )
+    assert _code(r, "youtube")["reasons"] == ["gone", "quota"]
+    assert _unread(r, "youtube") == ["how(x)"]
+
+
+def test_a_module_constant_is_read_only_as_mod_name_and_only_when_bound_once():
+    r = _scan(
+        urlguard="""
+        REASON_MALFORMED = "malformed"
+        TWICE = "a"
+        TWICE = "b"
+        if FLAG:
+            LATER = "c"
+        """,
+        routes__a="""
+        from app import urlguard
+
+        BARE = "bare"
+
+        def f():
+            raise HTTPException(409, {"code": "url_blocked", "reason": urlguard.REASON_MALFORMED})
+        def g():
+            raise HTTPException(409, {"code": "url_blocked", "reason": urlguard.TWICE})
+        def h():
+            raise HTTPException(409, {"code": "url_blocked", "reason": urlguard.LATER})
+        def i():
+            raise HTTPException(409, {"code": "url_blocked", "reason": BARE})
+        """,
+    )
+    assert _code(r, "url_blocked")["reasons"] == ["malformed"]
+    assert _unread(r, "url_blocked") == ["urlguard.TWICE", "urlguard.LATER", "BARE"]
+
+
+def test_a_name_imported_from_two_places_or_under_an_if_is_not_looked_up():
+    r = _scan(
+        m1='R = Literal["one"]',
+        m2='R = Literal["two"]',
+        a="""
+        def f():
+            from app.m1 import R
+        def g():
+            from app.m2 import R
+        def h(reason: R):
+            return HTTPException(409, {"code": "edit", "reason": reason})
+        """,
+        b="""
+        if FLAG:
+            from app.m1 import R
+        def h(reason: R):
+            return HTTPException(409, {"code": "playlist", "reason": reason})
+        """,
+        c="""
+        from app.m1 import R
+        def h(reason: R):
+            return HTTPException(409, {"code": "clip", "reason": reason})
+        """,
+    )
+    assert _code(r, "edit")["reasons"] == [] and _unread(r, "edit") == ["reason"]
+    assert _code(r, "playlist")["reasons"] == [] and _unread(r, "playlist") == ["reason"]
+    assert _code(r, "clip")["reasons"] == ["one"]
+
+
+def test_a_caught_exception_answers_with_the_literal_its_class_declares_on_self():
+    r = _scan(
+        errors="""
+        from typing import Literal
+        ClipReason = Literal["bad_range", "too_short"]
+        EditReason = Literal["not_media"]
+
+        class ClipError(Exception):
+            def __init__(self, reason: ClipReason, **params: float):
+                self.reason: ClipReason = reason
+                self.params = params
+
+        class EditError(Exception):
+            reason: EditReason
+
+        class Untyped(Exception):
+            def __init__(self, reason: str):
+                self.reason = reason
+
+        class Narrower(ClipError):
+            pass
+        """,
+        routes__a="""
+        from app import errors
+
+        def f():
+            try:
+                pass
+            except errors.ClipError as e:
+                raise HTTPException(422, {"code": "clip", "reason": e.reason})
+            except (errors.ClipError, errors.EditError) as e:
+                raise HTTPException(422, {"code": "clip", "reason": e.reason})
+            except errors.EditError as e:
+                raise HTTPException(422, {"code": "clip", "reason": e.reason})
+            except errors.Untyped as e:
+                raise HTTPException(422, {"code": "clip", "reason": e.reason})
+            except errors.Narrower as e:
+                raise HTTPException(422, {"code": "clip", "reason": e.reason})
+            except errors.ClipError as e:
+                raise HTTPException(422, {"code": "clip", "reason": e})
+        """,
+    )
+    assert _code(r, "clip")["reasons"] == ["bad_range", "too_short"]
+    assert _unread(r, "clip") == [
+        "e.reason",  # a tuple of classes
+        "e.reason (EditError.reason has no Literal type)",  # declared on the class body only
+        "e.reason (Untyped.reason has no Literal type)",
+        "e.reason (Narrower.reason has no Literal type)",  # a subclass: not looked up the bases
+        "e",  # the exception itself
+    ]
+
+
+def test_a_parameter_answers_with_its_literal_or_its_class_and_any_other_type_is_unread():
+    r = _scan(
+        a="""
+        from typing import Literal
+        Why = Literal["one", "two"]
+
+        class Err(Exception):
+            def __init__(self, reason: Literal["three"]):
+                self.reason: Literal["three"] = reason
+
+        def typed(reason: Why):
+            return HTTPException(409, {"code": "playlist", "reason": reason})
+        def inline(reason: Literal["four"]):
+            return HTTPException(409, {"code": "playlist", "reason": reason})
+        def by_class(exc: Err):
+            return HTTPException(409, {"code": "playlist", "reason": exc.reason})
+        def rebound(exc: Err):
+            exc = other()
+            return HTTPException(409, {"code": "playlist", "reason": exc.reason})
+        def optional(reason: Literal["five"] | None = None):
+            return HTTPException(409, {"code": "playlist", "reason": reason})
+        def quoted(reason: "Why"):
+            return HTTPException(409, {"code": "playlist", "reason": reason})
+        def number(reason: int):
+            return HTTPException(409, {"code": "playlist", "reason": reason})
+
+        class C:
+            def method(self, reason: str):
+                return HTTPException(409, {"code": "playlist", "reason": reason})
+        """
+    )
+    assert _code(r, "playlist")["reasons"] == ["four", "one", "three", "two"]
+    unread = _unread(r, "playlist")
+    # a parameter bound again, `| None`, a quoted annotation, `int`
+    assert unread[:4] == ["exc.reason", "reason", "reason", "reason"]
+    assert "method(reason) is not a module-level helper" in unread[4]
+    assert len(unread) == 5
+
+
+def test_a_str_helper_nobody_calls_sends_nothing():
+    r = _scan(
+        a="""
+        def helper(reason: str):
+            return HTTPException(409, {"code": "playlist", "reason": reason})
+        """
+    )
+    assert _code(r, "playlist") == {"reasons": [], "unread": [], "sites": 1, "reasonless": []}
+
+
+def test_a_map_lookup_is_its_values_and_its_keys_must_be_exactly_what_the_index_can_be():
+    src = """
+        from typing import Literal
+        SettingReason = Literal["too_low", "too_high"]
+
+        class InvalidSetting(ValueError):
+            def __init__(self, key: str, reason: SettingReason, **params: object):
+                self.reason: SettingReason = reason
+                self.params = params
+
+        _MAP: dict[SettingReason, str] = {{{keys}}}
+
+        def refused(status: int, reason: str, **params: object):
+            return HTTPException(status, {{**params, "code": "refused", "reason": reason}})
+
+        def setting_refused(exc: InvalidSetting):
+            return refused(400, _MAP[{index}], **exc.params)
+    """
+    both = '"too_low": "setting_too_low", "too_high": "setting_too_high"'
+    whole = _scan(a=src.format(keys=both, index="exc.reason"))
+    assert _code(whole, "refused")["reasons"] == ["setting_too_high", "setting_too_low"]
+    assert whole["errors"] == [] and whole["unreadCodes"] == []
+    for keys, index in [
+        ('"too_low": "setting_too_low"', "exc.reason"),  # a key short
+        (both + ', "gone": "setting_gone"', "exc.reason"),  # a key no index can be
+        (both, "exc.key"),  # an index the scan cannot read
+    ]:
+        r = _scan(a=src.format(keys=keys, index=index))
+        assert len(r["errors"]) == 1 and "not what its index can be" in r["errors"][0]
+
+
+def test_a_lookup_in_anything_but_a_module_dict_of_literal_keys_is_unread():
+    r = _scan(
+        a="""
+        BUILT = make()
+        NUMBERED = {1: "one"}
+
+        def f(table, k):
+            raise HTTPException(409, {"code": "edit", "reason": table[k]})
+        def g(k):
+            raise HTTPException(409, {"code": "edit", "reason": BUILT[k]})
+        def h(k):
+            raise HTTPException(409, {"code": "edit", "reason": NUMBERED[k]})
+        """
+    )
+    assert _unread(r, "edit") == ["table[k]", "BUILT[k]", "NUMBERED[k]"]
+    assert r["errors"] == []
+
+
+def test_a_code_must_be_one_literal():
+    r = _scan(
+        a="""
+        BUSY = "busy"
+        def f(code):
+            raise HTTPException(409, {"code": "busy"})
+        def g(code):
+            raise HTTPException(409, {"code": code})
+        def h():
+            raise HTTPException(409, {"code": BUSY})
+        def i(x):
+            raise HTTPException(409, {"code": "a" if x else "b"})
+        def j(x):
+            raise HTTPException(409, {"code": "a" if x else None})
+        def k(key):
+            raise HTTPException(409, {"code": "edit", key: "late"})
+        """
+    )
+    assert r["codes"]["busy"]["reasonless"] == ["a.py:4"]
+    assert set(r["codes"]) == {"busy"}
+    assert len(r["unreadCodes"]) == 5
+    assert r["unreadCodes"][-1].endswith(
+        "(a spread or a computed key the code and the reason do not follow)"
+    )
+
+
+def test_a_spread_or_a_computed_key_stands_before_both_the_code_and_the_reason():
+    def unread_codes(detail: str) -> list[str]:
+        return _scan(a=f"def f(x, more, key):\n    raise HTTPException(409, {detail})\n")[
+            "unreadCodes"
+        ]
+
+    assert unread_codes('{**more, "code": "refused", "reason": "a"}') == []
+    assert unread_codes('{key: 1, **more, "reason": "a", "code": "refused"}') == []
+    for late in [
+        '{"code": "refused", "reason": "a", **more}',  # the spread may replace both
+        '{"code": "refused", **more, "reason": "a"}',  # … the code
+        '{"reason": "a", **more, "code": "refused"}',  # … the reason
+        '{**more, "code": "refused"}',  # no reason after it: the spread may carry one
+        '{"code": "refused", "reason": "a", key: "x"}',  # a key that may be either
+        'dict(**more, code="refused", reason="a")',  # dict() raises on a repeated key
+        'dict(more, code="refused", reason="a")',
+    ]:
+        assert unread_codes(late), late
+
+
+def test_a_detail_stands_only_where_it_is_sent():
+    def result(body: str, extra: str = "") -> dict:
+        return _scan(a=f"def f(x, cached, fix):\n{textwrap.indent(body, '    ')}\n{extra}")
+
+    for body in [
+        'detail = {"code": "login", "reason": "a"}\nraise HTTPException(401, detail)',
+        'if (detail := {"code": "login", "reason": "a"}):\n    raise HTTPException(401, detail)',
+        'raise HTTPException(401, {"code": "login", "reason": "a"}.copy())',
+        'raise HTTPException(401, fix({"code": "login", "reason": "a"}))',
+        'raise HTTPException(401, cached or {"code": "login", "reason": "a"})',
+        'return JSONResponse({"code": "login", "reason": "a"}, status_code=401)',  # the whole body
+        'raise HTTPException(401, None, {"code": "login", "reason": "a"})',  # the headers
+        'raise HTTPException(401, headers={"code": "login", "reason": "a"})',
+        'raise HTTPException(401, "a" if {"code": "login", "reason": "a"} else "b")',
+    ]:
+        r = result(body)
+        assert r["unreadCodes"] and "login" not in r["codes"], body
+        assert "(a detail put where the scan cannot follow it)" in r["unreadCodes"][0], body
+    held = _scan(a='class C:\n    detail = {"code": "login"}\n')
+    assert "(a detail put where the scan cannot follow it)" in held["unreadCodes"][0]
+
+    sent = result(
+        'raise HTTPException(401, {"code": "login", "reason": "a"} if x else {"code": "login"})\n'
+        'raise HTTPException(401, detail=dict(code="login", reason="b"))\n'
+        'return JSONResponse(content={"detail": {"code": "login", "reason": "c"}})'
+    )
+    assert sent["unreadCodes"] == [] and _code(sent, "login")["reasons"] == ["a", "b", "c"]
+
+
+def test_a_factory_is_a_detail_only_when_each_return_is_one_and_each_call_is_sent():
+    factory = """
+def quota(e) -> dict:
+    return {"code": "quota", "reason": "files"}
+"""
+    sent = "def f(e):\n    raise HTTPException(422, detail=quota(e))\n"
+    assert _scan(a=factory + sent)["codes"]["quota"]["reasons"] == ["files"]
+    for change in [
+        "def g(e):\n    d = quota(e)\n    d['code'] = 'other'\n    raise HTTPException(422, d)\n",
+        "def g(e):\n    raise HTTPException(422, detail=quota(e).copy())\n",
+        "pick = quota\n",
+    ]:
+        r = _scan(a=factory + sent + change)
+        assert r["unreadCodes"] and "quota" not in r["codes"], change
+    twice = _scan(a="quota = None\n" + factory + sent)  # the def is the last of two bindings
+    assert twice["unreadCodes"] and "quota" not in twice["codes"]
+    for other in [
+        "    if e:\n        return None\n",
+        "    if e:\n        return cached\n",
+        "    if e:\n        return {'code': 'quota', 'reason': 'x'} if e > 1 else None\n",
+        "    log({'code': 'quota', 'reason': 'logged'})\n",  # a detail it does not return
+    ]:
+        bent = factory.replace("-> dict:\n", "-> dict:\n" + other)
+        assert _scan(a=bent + sent)["unreadCodes"], other
+    method = "class C:\n    def quota(self):\n        return {'code': 'quota', 'reason': 'm'}\n"
+    assert _scan(a=method)["unreadCodes"]
+    dotted = _scan(
+        a=factory,
+        routes__b="import app.a\n\ndef g(e):\n    raise HTTPException(422, detail=app.a.quota(e))\n",
+    )
+    assert dotted["unreadCodes"] and "quota" not in dotted["codes"]
+
+
+def test_a_name_a_lambda_a_comprehension_a_nonlocal_or_a_global_binds_is_unread():
+    r = _scan(
+        a="""
+        def f(svc):
+            why = "invalid"
+            make = lambda why: HTTPException(401, {"code": "login", "reason": why})
+            raise make(svc.state)
+        def g(svc):
+            why = "invalid"
+            raise [HTTPException(401, {"code": "login", "reason": why}) for why in svc.all][0]
+        def h(svc):
+            why = "invalid"
+            def inner():
+                nonlocal why
+                why = svc.reason
+            inner()
+            raise HTTPException(401, {"code": "login", "reason": why})
+        def i(svc):
+            global why
+            why = "invalid"
+            raise HTTPException(401, {"code": "login", "reason": why})
+        """
+    )
+    assert _code(r, "login")["reasons"] == []
+    assert sorted(_unread(r, "login")) == [
+        "why (bound by a lambda or a comprehension)",
+        "why (bound by a lambda or a comprehension)",
+        "why (named by a nonlocal or a global)",
+        "why (named by a nonlocal or a global)",
+    ]
+
+
+def test_a_local_that_reaches_itself_is_unread():
+    r = _scan(
+        a="""
+        def f(x):
+            why = "a"
+            if x:
+                why = why if x > 1 else "b"
+            raise HTTPException(409, {"code": "edit", "reason": why})
+        def g(x):
+            a = "z"
+            b = a
+            a = b
+            raise HTTPException(409, {"code": "playlist", "reason": a})
+        def h(x):
+            why = "c"
+            if x:
+                raise HTTPException(409, {"code": "busy", "reason": why})
+            raise HTTPException(409, {"code": "busy", "reason": why})
+        """
+    )
+    assert _code(r, "busy")["reasons"] == ["c"] and _code(r, "busy")["unread"] == []
+    assert _code(r, "edit")["reasons"] == ["a", "b"]
+    assert _unread(r, "edit") == ["why (reached again while it is resolved)"]
+    assert _code(r, "playlist")["reasons"] == ["z"]
+    assert any("reached again while it is resolved" in u for u in _unread(r, "playlist"))
+
+
+def test_a_module_constant_or_a_map_changed_elsewhere_is_unread():
+    def reasons(urlguard: str, route: str = "", **more: str) -> tuple[list[str], list[str]]:
+        r = _scan(
+            **more,
+            urlguard="REASON = 'malformed'\n_MAP = {'a': 'map_a'}\n" + urlguard,
+            routes__a="from app import urlguard\n"
+            + route
+            + "\ndef f(k: Literal['a']):\n"
+            + "    raise HTTPException(409, {'code': 'url_blocked', 'reason': urlguard.REASON})\n"
+            + "    raise HTTPException(409, {'code': 'url_blocked', 'reason': urlguard._MAP[k]})\n",
+        )
+        return _code(r, "url_blocked")["reasons"], _unread(r, "url_blocked")
+
+    assert reasons("def get(k):\n    return _MAP.get(k)\n") == (["malformed", "map_a"], [])
+    other = "from app import other\ndef g():\n    other.REASON = 'x'\n"  # another module's REASON
+    assert reasons("", other, other="REASON = 'y'\n") == (["malformed", "map_a"], [])
+    shadow = (
+        "def h(*urlguard):\n"
+        "    raise HTTPException(409, {'code': 'url_blocked', 'reason': urlguard.REASON})\n"
+    )
+    assert reasons("", shadow)[1] == ["urlguard.REASON"]
+    for urlguard, route in [
+        ("def reset():\n    global REASON\n    REASON = 'x'\n", ""),
+        ("", "def g():\n    urlguard.REASON = 'x'\n"),
+        ("", "def g():\n    del urlguard.REASON\n"),
+    ]:
+        assert reasons(urlguard, route)[0] == ["map_a"], (urlguard, route)
+    for urlguard in [
+        "_MAP['a'] = compute()\n",
+        "def init(x):\n    _MAP['a'] = x\n",
+        "_MAP.update(a='other')\n",
+        "def drop():\n    del _MAP['a']\n",
+        "register(_MAP)\n",
+    ]:
+        got, unread = reasons(urlguard)
+        assert got == ["malformed"] and "(the map is changed after it is built)" in unread[0]
+
+
+def test_a_helper_bound_twice_is_not_followed():
+    r = _scan(
+        refusal="refused = None\n" + textwrap.dedent(REFUSAL),
+        routes__a="from app.refusal import refused\n\ndef f():\n    raise refused(409, 'lost')\n",
+    )
+    assert _code(r, "refused")["reasons"] == []
+    assert _unread(r, "refused")[0].endswith("refused(reason) is not a module-level helper")
+
+
+def test_a_dotted_path_through_an_app_module_that_goes_nowhere_is_unread():
+    r = scan(
+        {
+            "__init__.py": "",
+            "refusal.py": textwrap.dedent(REFUSAL),
+            "routes/a.py": "import app as a\n\ndef f():\n    raise a.refusal.refused(409, 'dotted')\n",
+        }
+    )
+    assert _unread(r, "refused") == ["a.refusal.refused (a reference the scan cannot resolve)"]
+
+
+def test_a_helper_reached_through_an_app_module_that_does_not_bind_it_is_unread():
+    for shim in [
+        "from app.refusal import *\n",
+        "try:\n    from app.refusal import refused\nexcept ImportError:\n    refused = None\n",
+    ]:
+        r = _scan(
+            refusal=REFUSAL,
+            shim=shim,
+            routes__a="from app.shim import refused\n\ndef f():\n    raise refused(409, 'hidden')\n",
+        )
+        assert _unread(r, "refused") == ["refused (a reference the scan cannot resolve)"], shim
+    package = scan(
+        {
+            "pkg/refusal.py": textwrap.dedent(REFUSAL),
+            "pkg/__init__.py": "from .refusal import refused\n",
+            "routes/a.py": "from app.pkg import refused\n\ndef f():\n    raise refused(409, 'hidden')\n",
+        }
+    )
+    assert _unread(package, "refused") == ["refused (a reference the scan cannot resolve)"]
+
+
+def test_the_data_files_are_excluded_by_name_only():
+    r = _scan(
+        plex__tmdb='def f():\n    return {"code": "HU", "name": "Hungary"}',
+        plex__other='def f():\n    return {"code": "HU"}',
+    )
+    assert r["excluded"] == {"plex/tmdb.py": 1}
+    assert "HU" in r["codes"]
+
+
+def test_the_app_scans():
+    """The real tree, on the interpreter the backend runs: every refusal it holds is read (the
+    frontend's contract judges what is read)."""
+    result = scan_app()
+    assert {"refused", "not_found", "login", "clip"} <= set(result["codes"])
+    assert result["errors"] == [] and result["unreadCodes"] == []

backend/tests/test_video_row.py

@@ -0,0 +1,47 @@
+"""A catalog video as the feed lists it, the row a player opened from an address starts from. DB lane."""
+
+from datetime import datetime, timezone
+
+from app.catalog.models import Channel, Video
+from app.reader.models import VideoState
+
+
+def _video(db, vid="v1"):
+    db.add(Channel(id="UCo", title="Owner", handle="@owner"))
+    db.flush()
+    db.add(
+        Video(
+            id=vid,
+            title="A talk",
+            channel_id="UCo",
+            published_at=datetime.now(timezone.utc),
+            duration_seconds=3600,
+        )
+    )
+    db.commit()
+
+
+def test_a_video_comes_as_the_feed_row_with_my_own_state(db, make_user, as_user):
+    me, other = make_user(), make_user()
+    _video(db)
+    db.add(VideoState(user_id=me.id, video_id="v1", status="new", position_seconds=600))
+    db.add(VideoState(user_id=other.id, video_id="v1", status="watched", position_seconds=90))
+    db.commit()
+    r = as_user(me).get("/api/videos/v1/row")
+    assert r.status_code == 200, r.text
+    row = r.json()
+    assert (row["id"], row["title"], row["channel_title"]) == ("v1", "A talk", "Owner")
+    assert (row["status"], row["position_seconds"]) == ("new", 600)
+    assert row["watch_url"] == "https://www.youtube.com/watch?v=v1"
+
+
+def test_a_video_never_opened_has_no_state(db, make_user, as_user):
+    _video(db)
+    row = as_user(make_user()).get("/api/videos/v1/row").json()
+    assert (row["status"], row["position_seconds"], row["saved"]) == ("new", 0, False)
+
+
+def test_a_video_outside_the_catalog_is_not_found(db, make_user, as_user):
+    r = as_user(make_user()).get("/api/videos/nope/row")
+    assert r.status_code == 404
+    assert r.json()["detail"]["code"] == "not_found"

docs/DESIGN.md

@@ -378,7 +378,11 @@ Which actions are visible and which live in a menu.
   managing the shares, re-download, the copies, cancel / delete / remove
   behind their confirms); a link inside a row keeps the browser's own right-click menu. A notification
   row keeps its link and its unread mark, shows its dismiss on hover (in the "…" on touch), and its
-  "…" holds find / undo for an activity notice. The notification center's band keeps Mark all read
+  "…" holds find / undo for an activity notice. The notification center lists what asks for the
+  reader first ("Needs you · n": an unread row, a notice waiting on an action — one read during the
+  visit keeps its place there until Mark all read), then one stream of both sources, newest first,
+  and folds read rows older than a week under "Earlier (n)", a heading-style disclosure, closed — Back to a row
+  that folded away since opens it on that row. Its band keeps Mark all read
   and puts Clear everything, now behind a confirm, in its "…"; the Scheduler's strip keeps Run all
   and Pause and puts Purge discovery in its "…". A list whose row objects are rebuilt each render or replaced by a
   poll passes `useContextMenu({ keyOf })` (its id), so the "…" still closes its own menu. A menu's
@@ -824,3 +828,4 @@ of a full-width panel and nothing on the right.
 | 2026-10-25 | Player panel glyphs (owner 1A, 2A, 3)            | In the side panel the queue row is glyph-only on one line, and Mark watched is a glyph toggle among the actions (✓ / ✓✓); the docked bar keeps its labels; the related switch at the default size, "Trending"                                                                                                                                                                                       | Labelled buttons wrapping onto three lines; glyphs on the docked bar too; Mark watched on its own line                                                                                                 | The panel is narrow and the list controls are the same few every time; each glyph keeps its full name and shortcut in its tooltip; the docked bar has the width for words                                                    |
 | 2026-10-25 | Auto-advance glyphs (owner E A, H a)             | Auto-advance wears list glyphs (`ListEnd` next and off, `ListStart` previous, `Shuffle` random), in the panel and the docked bar; the auto-advance and loop cycles are `lit`, not `pressed`                                                                                                                                                                                                         | The skip arrows for the mode; an X'd list for off; `aria-pressed` on a cycle                                                                                                                           | Beside Previous / Next the skip arrows read as a second Next; a cycle of three or four modes is no two-state switch, and its name already says which                                                                         |
 | 2026-10-25 | Restart and Reset glyphs (owner L A)             | A menu's Play from the beginning wears `RotateCcw`, as the card's own Restart does; Reset (clear progress and status) wears `Eraser`; Redownload wears `RefreshCw`, the retry arrow                                                                                                                                                                                                                 | The skip arrow ⏮ on the menu's Restart; `RotateCcw` on both Restart and Reset; `TimerReset` for Restart                                                                                               | ⏮ is Previous beside the player; one action wore two glyphs, and two actions in one menu would have worn one                                                                                                                |
+| 2026-10-28 | Notification order (owner A-D1 a, A-D2 a, ★ a)   | What asks for the reader first, from either source ("Needs you · n"), then one stream newest first; read rows older than a week fold under "Earlier (n)", closed, its label in the section-heading style with a chevron                                                                                                                                                                             | One stream with no band; this browser's activity above the server's (the two fixed sections); a server-side retention that deletes old rows                                                            | An admin's access requests sat under up to a hundred server rows; week-old read notices crowded what is new; folding keeps the rows (nothing is deleted) and an unread row never folds, whatever its age                     |

docs/development.md

@@ -45,7 +45,18 @@ A frontend page is one folder, `frontend/src/modules/<id>/` (the layering is in
    page renders into the floating header itself through `PageHeader`; the shell knows no page.
 2. `module.ts`: its `ModuleDef` (`lib/moduleDef.ts`): id, label keys, icon, an optional `gate`, the page as a
    `lazyWithPreload(() => import(…))`, and optionally a rail and a `Store`. Of its own folder it imports statically
-   only its store (a `…Provider` / `…Store` file); the page and the rail load lazily.
+   only its store (a `…Provider` / `…Store` file); the page and the rail load lazily. `urlKeys` names every
+   address-bar key its view writes (the URL is the view: a bookmark reopens it), its list kept in `lib/` beside
+   its codec; the shell clears them on a page switch and opens a page without another page's keys.
+   Every setting the page shows — a tab, a sort, a filter, a search, the item open in it — goes there: a codec
+   in `lib/<id>UrlState.ts` (read the params into the view, write the view as updates, a default left out —
+   or always written, when an address naming none falls back to a view remembered elsewhere), written with
+   `useUrlMirror` (a sub-view through `useHistorySubview`'s `url`, an overlay through `useBackToClose`'s),
+   always as the codec's result: a writer outside `lib/` computes no key of its own. Read back first on mount
+   (a link wins over anything remembered). A key that carries typed text — a search box's, a column filter
+   map with a text filter — is also in `typedUrlKeys` (the client log keeps what was typed out). Add its round
+   trip to `e2e/bookmark.spec.ts`, tagged with the page (`{ tag: "@<id>" }`). Only what an address cannot promise to
+   reopen stays out, said in its codec (Home's draw, `lib/homeUrlState`).
 3. `index.ts`, the module's public face: the definition, and only what other folders must read (its store's
    hooks). Another folder reaches the module through this file or not at all.
 4. The id in `lib/urlState`'s `PAGES`, and the definition in `features/navigation/moduleRegistry.ts`, in
@@ -58,7 +69,10 @@ A frontend page is one folder, `frontend/src/modules/<id>/` (the layering is in
    returns to `ui/FilterRail`; tsc names each table still missing the new id.
 
 What holds it: `moduleRegistry.contract.test.ts` (every id defined once, from its own folder, lazily),
-`moduleStores.contract.test.tsx` (no store reads another module), the `local/layers` lint rule (imports only go
+`moduleStores.contract.test.tsx` (no store reads another module), `moduleUrl.contract.test.ts` (each URL key
+belongs to one module and matches what its codec writes; a writer outside `lib/` is handed a literal or a `lib/`
+function's result, never a key of its own; no key literal written or read from the live query undeclared; every key
+sorted as typed or not; every page with keys in a tagged bookmark round trip), the `local/layers` lint rule (imports only go
 down, a module only through its face) and `chunkGuard` in the build (no lazy page on the boot path), plus the
 i18n parity test.
 
@@ -130,7 +144,8 @@ npm run typecheck     # tsc x3 (app / node / e2e)
 npm run lint          # eslint (typed rules included; warnings fail)
 npm run format:check  # prettier
 npm run knip          # unused files/exports/deps
-npm run test          # vitest (incl. the compiler and gate-register contracts)
+npm run test          # vitest (incl. the compiler and gate-register contracts; the refusal contract runs
+                      # the host's `python` on backend/tests/refusal_sites.py, stdlib only)
 npx vite build        # the production bundle (devOnlyGuard fails it on dev-only code, chunkGuard on a lazy page loaded at boot)
 npm audit --omit=dev --audit-level=high   # what ships to the browser, at high or above
 ```

frontend/e2e/bookmark.spec.ts

@@ -0,0 +1,259 @@
+import { test, expect, type Browser, type Page } from "@playwright/test";
+import {
+  clickVisibleChannelLink,
+  expectContentType,
+  gotoPage,
+  openApp,
+  openFirstVideo,
+  toggleContentType,
+} from "./helpers";
+
+// The address is the view: a view set through the UI, its address opened as a bookmark — in a NEW
+// browser context, so nothing this tab remembered (its history entries, sessionStorage, the view
+// storage it wrote) can stand in for what the address says. One round trip per page that names its
+// view, tagged with the page (moduleUrl.contract.test holds the tags to the module definitions),
+// plus the overlays the shell opens over any page (the channel page, the player) and the live
+// search. Not Plex: what it shows is the instance's own library, which a test stack may not have.
+
+const STORAGE_STATE = "e2e/.auth/state.json";
+
+/** The page's address, opened as a bookmark in a fresh context of the same account. */
+async function bookmarked(browser: Browser, page: Page, prepare?: (p: Page) => Promise<void>) {
+  const url = page.url();
+  const ctx = await browser.newContext({ storageState: STORAGE_STATE, locale: "en-US" });
+  const fresh = await ctx.newPage();
+  await prepare?.(fresh);
+  await openApp(fresh, url);
+  return fresh;
+}
+
+const tab = (p: Page, name: string) => p.getByRole("tab", { name, exact: true });
+const column = (p: Page, name: string) =>
+  p.getByRole("columnheader", { name: new RegExp(`^${name}`) });
+
+async function gotoAdminPage(page: Page, id: string): Promise<void> {
+  await page.getByTestId("nav-admin").click();
+  await page.getByTestId(`nav-admin-${id}`).click();
+}
+
+test.describe("a bookmark reopens the view it was taken of", () => {
+  test("the feed's filters", { tag: "@feed" }, async ({ page, browser }) => {
+    await openApp(page, "/?page=feed");
+    await toggleContentType(page, "includeLive");
+    await expect(page).toHaveURL(/[?&]live=/);
+    const fresh = await bookmarked(browser, page);
+    await expectContentType(fresh, "includeLive", true);
+    await fresh.context().close();
+  });
+
+  test("Home's time budget", { tag: "@home" }, async ({ page, browser }) => {
+    await openApp(page, "/?page=home");
+    await page.getByRole("button", { name: "An evening", exact: true }).click();
+    await expect(page).toHaveURL(/[?&]hb=long/);
+    const fresh = await bookmarked(browser, page);
+    await expect(fresh.getByRole("button", { name: "An evening", exact: true })).toHaveAttribute(
+      "aria-pressed",
+      "true",
+    );
+    await fresh.context().close();
+  });
+
+  test("a Settings tab", { tag: "@settings" }, async ({ page, browser }) => {
+    await openApp(page, "/?page=feed");
+    await gotoPage(page, "settings");
+    await tab(page, "Notifications").click();
+    const fresh = await bookmarked(browser, page);
+    await expect(tab(fresh, "Notifications")).toHaveAttribute("aria-selected", "true");
+    await fresh.context().close();
+  });
+
+  test("an admin page's tab", { tag: "@users" }, async ({ page, browser }) => {
+    await openApp(page, "/?page=feed");
+    await gotoAdminPage(page, "users");
+    await tab(page, "Access requests").click();
+    const fresh = await bookmarked(browser, page);
+    await expect(tab(fresh, "Access requests")).toHaveAttribute("aria-selected", "true");
+    await fresh.context().close();
+  });
+
+  test("a Configuration group", { tag: "@config" }, async ({ page, browser }) => {
+    await openApp(page, "/?page=feed");
+    await gotoAdminPage(page, "config");
+    const second = page.getByRole("tab").nth(1);
+    const name = (await second.textContent()) ?? "";
+    await second.click();
+    await expect(page).toHaveURL(/[?&]cfgtab=/);
+    const fresh = await bookmarked(browser, page);
+    await expect(fresh.getByRole("tab", { name, exact: true })).toHaveAttribute(
+      "aria-selected",
+      "true",
+    );
+    await fresh.context().close();
+  });
+
+  test("the Activity tab and its time window", { tag: "@activity" }, async ({ page, browser }) => {
+    await openApp(page, "/?page=feed");
+    await gotoAdminPage(page, "activity");
+    await tab(page, "Server log").click();
+    await page.getByRole("button", { name: "30 days", exact: true }).click();
+    await expect(page).toHaveURL(/[?&]aw=30d/);
+    const fresh = await bookmarked(browser, page);
+    await expect(tab(fresh, "Server log")).toHaveAttribute("aria-selected", "true");
+    await expect(fresh.getByRole("button", { name: "30 days", exact: true })).toHaveAttribute(
+      "aria-pressed",
+      "true",
+    );
+    await fresh.context().close();
+  });
+
+  test("a playlist and its sort", { tag: "@playlists" }, async ({ page, browser }) => {
+    await openApp(page, "/?page=feed");
+    await gotoPage(page, "playlists");
+    await expect(column(page, "Title")).toBeVisible();
+    await column(page, "Title").getByRole("button").first().click();
+    await expect(page).toHaveURL(/[?&]plsort=/);
+    const sorted = await column(page, "Title").getAttribute("aria-sort");
+    const fresh = await bookmarked(browser, page);
+    await expect(column(fresh, "Title")).toHaveAttribute("aria-sort", sorted ?? "");
+    expect(new URL(fresh.url()).searchParams.get("pl")).toBe(
+      new URL(page.url()).searchParams.get("pl"),
+    );
+    await fresh.context().close();
+  });
+
+  test(
+    "the Channels manager's tab and name search",
+    { tag: "@channels" },
+    async ({ page, browser }) => {
+      await openApp(page, "/?page=feed");
+      await gotoPage(page, "channels");
+      await tab(page, "Hidden").click();
+      await page.getByPlaceholder("Search channels…").fill("zz");
+      await expect(page).toHaveURL(/zz/); // written once the typing settles
+      const fresh = await bookmarked(browser, page);
+      await expect(tab(fresh, "Hidden")).toHaveAttribute("aria-selected", "true");
+      await expect(fresh.getByPlaceholder("Search channels…")).toHaveValue("zz");
+      await fresh.context().close();
+    },
+  );
+
+  test("the Files search", { tag: "@files" }, async ({ page, browser }) => {
+    await openApp(page, "/?page=feed");
+    await gotoPage(page, "files");
+    await page.getByPlaceholder("Search files…").fill("zz");
+    await expect(page).toHaveURL(/zz/);
+    const fresh = await bookmarked(browser, page);
+    await expect(fresh.getByPlaceholder("Search files…")).toHaveValue("zz");
+    await fresh.context().close();
+  });
+
+  // A file of the test's own, uploaded for it and deleted after, and the account's sort put back:
+  // the account is left as it was found.
+  test(
+    "the Files sort, and the file open in the viewer",
+    { tag: "@files" },
+    async ({ page, browser }) => {
+      await openApp(page, "/?page=feed");
+      const NAME = "bookmark-note";
+      // One a run cut short left behind goes first.
+      const left = (await (await page.request.get("/api/files")).json()) as Record<
+        string,
+        unknown
+      >[];
+      for (const f of left.filter((f) => JSON.stringify(f).includes(`"${NAME}`)))
+        await page.request.delete(`/api/files/${String(f.id)}`);
+      const up = await page.request.post("/api/files/upload", {
+        headers: { "X-Upload-Filename": `${NAME}.txt` },
+        data: Buffer.from("a note the bookmark reopens\n"),
+      });
+      expect(up.ok(), await up.text()).toBeTruthy();
+      const { id } = (await up.json()) as { id: number };
+      // The account's own sort, put back after: a header press cycles it (asc, desc, none), so the
+      // case starts from none, as the address names it, whatever an earlier run left.
+      const me = (await (await page.request.get("/api/me")).json()) as {
+        preferences?: Record<string, unknown>;
+      };
+      const ownSort = me.preferences?.filesSort ?? null;
+      try {
+        await openApp(page, "/?page=files&fsort=none");
+        await column(page, "Name").getByRole("button").first().click();
+        await expect(page).toHaveURL(/[?&]fsort=name/);
+        const sorted = await column(page, "Name").getAttribute("aria-sort");
+        await page.getByText(NAME, { exact: true }).first().click();
+        await expect(page).toHaveURL(new RegExp(`[?&]fview=${id}`));
+        const fresh = await bookmarked(browser, page);
+        await expect(fresh.getByRole("dialog", { name: NAME })).toBeVisible();
+        await fresh.keyboard.press("Escape");
+        await expect(column(fresh, "Name")).toHaveAttribute("aria-sort", sorted ?? "");
+        await fresh.context().close();
+      } finally {
+        await page.request.delete(`/api/files/${id}`);
+        await page.request.put("/api/me/preferences", { data: { filesSort: ownSort } });
+      }
+    },
+  );
+
+  test("a channel page's own tab, over the page it was opened from", async ({ page, browser }) => {
+    await openApp(page, "/?page=feed");
+    await expect(page.getByTestId("video-card").first()).toBeVisible();
+    await clickVisibleChannelLink(page);
+    const title = await page.getByTestId("channel-title").textContent();
+    await tab(page, "About").click();
+    const fresh = await bookmarked(browser, page);
+    await expect(fresh.getByTestId("channel-title")).toHaveText(title ?? "");
+    await expect(tab(fresh, "About")).toHaveAttribute("aria-selected", "true");
+    await fresh.context().close();
+  });
+
+  test("the player and the video it plays", async ({ page, browser }) => {
+    await openApp(page, "/?page=feed");
+    await openFirstVideo(page);
+    await expect(page).toHaveURL(/[?&]watch=/);
+    const watch = new URL(page.url()).searchParams.get("watch");
+    const fresh = await bookmarked(browser, page);
+    await expect(fresh.getByTestId("player-modal")).toBeVisible();
+    expect(new URL(fresh.url()).searchParams.get("watch")).toBe(watch);
+    await fresh.context().close();
+  });
+
+  // The search itself never reaches YouTube here: the answer is the server's shape, served by the
+  // test, and the request it answers is what the address named. The instance's search settings are
+  // pinned too (the free source, switched on): a stack left on the API source reopens the search
+  // waiting for its press, by design, and one with search off offers none.
+  test(
+    "a live YouTube search, its term and its count",
+    { tag: "@feed" },
+    async ({ page, browser }) => {
+      const answer = async (p: Page, seen: string[]) => {
+        await p.route("**/api/me", async (route) => {
+          const me = (await (await route.fetch()).json()) as Record<string, unknown>;
+          return route.fulfill({ json: { ...me, search_source: "scrape", search_enabled: true } });
+        });
+        await p.route("**/api/search/youtube?**", (route) => {
+          seen.push(route.request().url());
+          return route.fulfill({ json: { items: [], next_cursor: null, source: "scrape" } });
+        });
+      };
+      await answer(page, []);
+      await openApp(page, "/?page=feed");
+      await page.getByPlaceholder("Search your subscriptions…").fill("lofi");
+      await page.getByRole("button", { name: "Search YouTube", exact: true }).click();
+      await expect(page.getByText("YouTube results for “lofi”")).toBeVisible();
+      await expect(page).toHaveURL(/[?&]yt=lofi/); // named as it opens, not only once the count is set
+      await page.getByRole("button", { name: "40", exact: true }).click();
+      await expect(page).toHaveURL(/[?&]ytn=40/);
+
+      const seen: string[] = [];
+      const fresh = await bookmarked(browser, page, (p) => answer(p, seen));
+      await expect(fresh.getByText("YouTube results for “lofi”")).toBeVisible();
+      await expect(fresh.getByRole("button", { name: "40", exact: true })).toHaveAttribute(
+        "aria-pressed",
+        "true",
+      );
+      await expect.poll(() => seen.length).toBeGreaterThan(0);
+      const asked = new URL(seen[0]!).searchParams;
+      expect([asked.get("q"), asked.get("limit")]).toEqual(["lofi", "40"]);
+      await fresh.context().close();
+    },
+  );
+});

frontend/e2e/channel.spec.ts

@@ -48,7 +48,7 @@ test.describe("channel view", () => {
     // `.first()` here would grab an overscan card ABOVE the viewport, and Playwright's scroll-into-
     // view would move the feed before navigating, so Back would restore that moved position, not
     // the one under test. (This is what made the test fail while the app was in fact correct.)
-    expect(await clickVisibleChannelLink(page)).toBe(true);
+    await clickVisibleChannelLink(page);
     await expect(page.getByTestId("channel-title")).toBeVisible();
     await page.getByTestId("channel-back").click();
     await expect(page.getByTestId("video-card").first()).toBeVisible();

frontend/e2e/helpers.ts

@@ -33,23 +33,41 @@ export async function gotoPage(page: Page, id: string): Promise<void> {
  * that then asserts on where the feed was. Being inside the viewport is not enough either: a card
  * can sit under the page chrome above the scroller (the update banner, the toolbar band), and the
  * covered click makes Playwright scroll and retry — the same move (webkit failed 3 in 24).
- * So the link must be the element hit at its own centre. Returns false if none found.
+ * So the link must be the element hit at its own centre; none within the wait fails the test, with
+ * the poll's own message. Looked for again until one is, not once: a fresh load is still settling
+ * when the first card shows (the links move down ~55px), and webkit can answer the hit test at a
+ * link's new centre with the card under it — every link missed in 1 of 30 runs. A link that goes
+ * away mid-look (its evaluate waits for it, or throws) counts as not hit, so the next look runs.
  */
-export async function clickVisibleChannelLink(page: Page): Promise<boolean> {
+export async function clickVisibleChannelLink(page: Page): Promise<void> {
   const links = page.getByTestId("video-card-channel").filter({ visible: true });
-  const count = await links.count();
-  for (let i = 0; i < count; i++) {
-    const hittable = await links.nth(i).evaluate((el) => {
-      const r = el.getBoundingClientRect();
-      const hit = document.elementFromPoint(r.left + r.width / 2, r.top + r.height / 2);
-      return hit !== null && el.contains(hit);
-    });
-    if (hittable) {
-      await links.nth(i).click();
-      return true;
+  let index = -1;
+  const findHittable = async () => {
+    const count = await links.count();
+    for (let i = 0; i < count; i++) {
+      const hittable = await links
+        .nth(i)
+        .evaluate(
+          (el) => {
+            const r = el.getBoundingClientRect();
+            const hit = document.elementFromPoint(r.left + r.width / 2, r.top + r.height / 2);
+            return hit !== null && el.contains(hit);
+          },
+          undefined,
+          { timeout: 1000 },
+        )
+        .catch(() => false);
+      if (hittable) return i;
     }
-  }
-  return false;
+    return -1;
+  };
+  await expect
+    .poll(async () => (index = await findHittable()), {
+      message: "a channel link hit at its own centre",
+      timeout: 5000,
+    })
+    .toBeGreaterThan(-1);
+  await links.nth(index).click();
 }
 
 /**

frontend/eslint.config.js

@@ -898,7 +898,8 @@ export default tseslint.config(
     plugins: { playwright },
     rules: {
       "playwright/no-focused-test": "error",
-      "playwright/no-skipped-test": "error",
+      // fixme too: a test Playwright never runs, which the bookmark net would still count.
+      "playwright/no-skipped-test": ["error", { disallowFixme: true }],
     },
   },
   {

frontend/src/PlaylistEditFailures.dom.test.tsx

@@ -22,7 +22,7 @@ vi.mock("react-i18next", async (importOriginal) => {
 });
 vi.mock("./components/ui/confirmContext", () => ({ useConfirm: () => async () => true }));
 const { notify } = vi.hoisted(() => ({
-  notify: vi.fn((_n: { level: string; message: string }) => 0),
+  notify: vi.fn((_n: { level: string; message: NotifText }) => 0),
 }));
 vi.mock("./lib/notifications", async (importOriginal) => ({
   ...(await importOriginal<typeof import("./lib/notifications")>()),
@@ -35,6 +35,7 @@ import PlexPlaylistAdd from "./features/plexCards/PlexPlaylistAdd";
 import TagManager from "./features/channel/TagManager";
 import { api, HttpError, type PlexCard } from "./lib/api";
 import { qk } from "./lib/queryKeys";
+import type { NotifText } from "./lib/notifications";
 
 beforeAll(() => {
   class Stub {
@@ -98,7 +99,7 @@ describe("the Plex playlist page", () => {
       () => fireEvent.contextMenu(screen.getByText("Movie 1").closest("[data-nav-index]")!),
       "plex.playlist.removeFromPlaylist",
     );
-    await waitFor(() => expect(errors()).toEqual(["gone playlist"]));
+    await waitFor(() => expect(errors()).toEqual([{ detail: gone("playlist").detailData }]));
     await act(async () => void (await new Promise((r) => setTimeout(r, 20))));
     expect(screen.getByText("Movie 1")).toBeTruthy();
   });
@@ -119,7 +120,7 @@ describe("the Plex playlist page", () => {
     const field = await screen.findByDisplayValue("Films");
     fireEvent.change(field, { target: { value: "Movies" } });
     fireEvent.keyDown(field, { key: "Enter" });
-    await waitFor(() => expect(errors()).toEqual(["gone playlist"]));
+    await waitFor(() => expect(errors()).toEqual([{ detail: gone("playlist").detailData }]));
     expect(screen.getByDisplayValue("Movies")).toBeTruthy(); // still open to try again
   });
 
@@ -154,7 +155,7 @@ describe("the add-to-playlist popover", () => {
     );
     fireEvent.click(screen.getByLabelText("playlists.addToPlaylist"));
     fireEvent.click(await screen.findByRole("menuitemcheckbox", { hidden: true }));
-    await waitFor(() => expect(errors()).toEqual(["gone playlist"]));
+    await waitFor(() => expect(errors()).toEqual([{ detail: gone("playlist").detailData }]));
     await waitFor(() => expect(lists.mock.calls.length).toBeGreaterThan(1));
   });
 
@@ -282,7 +283,7 @@ describe("the add-to-playlist popover", () => {
     fireEvent.click(await screen.findByText("Gone"));
     // The server's own localized reason wins over the caller's fallback when the detail is
     // STRUCTURED — same as the twin above. What is under test is that anything is said at all.
-    await waitFor(() => expect(errors()).toEqual(["gone playlist"]));
+    await waitFor(() => expect(errors()).toEqual([{ detail: gone("playlist").detailData }]));
     await waitFor(() => expect(lists.mock.calls.length).toBeGreaterThan(1));
   });
 });
@@ -300,7 +301,7 @@ describe("the tag manager", () => {
       </QueryClientProvider>,
     );
     fireEvent.click(await screen.findByLabelText("tagManager.delete"));
-    await waitFor(() => expect(errors()).toEqual(["gone tag"]));
+    await waitFor(() => expect(errors()).toEqual([{ detail: gone("tag").detailData }]));
     await waitFor(() => expect(tags.mock.calls.length).toBeGreaterThan(1));
   });
 });

frontend/src/WriteFailureReporting.dom.test.tsx

@@ -19,7 +19,7 @@ vi.mock("react-i18next", async (importOriginal) => {
 });
 vi.mock("./components/ui/confirmContext", () => ({ useConfirm: () => async () => true }));
 const { notify } = vi.hoisted(() => ({
-  notify: vi.fn((_n: { level: string; title?: string; message: string }) => 0),
+  notify: vi.fn((_n: { level: string; title?: NotifText; message: NotifText }) => 0),
 }));
 vi.mock("./lib/notifications", async (importOriginal) => ({
   ...(await importOriginal<typeof import("./lib/notifications")>()),
@@ -30,6 +30,7 @@ import PlexCollectionEditor from "./modules/plex/PlexCollectionEditor";
 import UploadDialog from "./modules/files/UploadDialog";
 import DownloadDialog from "./features/downloads/DownloadDialog";
 import { api, HttpError } from "./lib/api";
+import { msg, type NotifText } from "./lib/notifications";
 
 beforeAll(() => {
   class Stub {
@@ -87,7 +88,7 @@ describe("the Plex collection editor", () => {
     );
     mount();
     fireEvent.click(await screen.findByText("Marathon"));
-    await waitFor(() => expect(errors()).toEqual(["plex.collection.editFailed"]));
+    await waitFor(() => expect(errors()).toEqual([msg("plex.collection.editFailed")]));
   });
 
   it("says so when enabling editing is refused", async () => {
@@ -97,7 +98,7 @@ describe("the Plex collection editor", () => {
     );
     mount();
     fireEvent.click(await screen.findByText("plex.collEditor.makeEditable"));
-    await waitFor(() => expect(errors()).toEqual(["plex.collection.editFailed"]));
+    await waitFor(() => expect(errors()).toEqual([msg("plex.collection.editFailed")]));
   });
 
   it("says so when a CONFIRMED delete does not happen", async () => {
@@ -108,7 +109,7 @@ describe("the Plex collection editor", () => {
     );
     mount();
     fireEvent.click(await screen.findByText("plex.collEditor.delete"));
-    await waitFor(() => expect(errors()).toEqual(["plex.collection.deleteFailed"]));
+    await waitFor(() => expect(errors()).toEqual([msg("plex.collection.deleteFailed")]));
   });
 });
 
@@ -144,7 +145,7 @@ describe("the upload dialog", () => {
     mount();
     pick();
     fireEvent.click(screen.getByText("downloads.upload.submit"));
-    await waitFor(() => expect(errors()).toEqual(["downloads.upload.failed"]));
+    await waitFor(() => expect(errors()).toEqual([msg("downloads.upload.failed")]));
   });
 
   it("says nothing when the user cancelled it themselves", async () => {
@@ -172,6 +173,6 @@ describe("the download dialog", () => {
     );
     await screen.findByText("Best");
     fireEvent.click(screen.getByText("downloads.dialog.submit"));
-    await waitFor(() => expect(errors()).toEqual(["errors.writeFailed.enqueueDownload"]));
+    await waitFor(() => expect(errors()).toEqual([msg("errors.writeFailed.enqueueDownload")]));
   });
 });

frontend/src/components/ui/Modal.dom.test.tsx

@@ -21,9 +21,9 @@ vi.mock("react-i18next", async (importOriginal) => {
 vi.mock("../../lib/history", () => ({ useBackToClose: () => {} }));
 
 import Modal from "./Modal";
-import { clearAll, notify } from "../../lib/notifications";
+import { clearAll, notify, raw } from "../../lib/notifications";
 import { pushLayer, removeLayer, useLayer } from "../../lib/layerStack";
-import { flushSync } from "react-dom";
+import { createPortal, flushSync } from "react-dom";
 
 // Fire a keydown on window (where Modal installs its handler), inside act.
 const press = (key: string, shiftKey = false) =>
@@ -121,7 +121,7 @@ describe("Modal focus trap (offsetParent stubbed 'visible')", () => {
         <Body />
       </Modal>,
     );
-    act(() => void notify({ level: "info", message: "Saved" }));
+    act(() => void notify({ level: "info", message: raw("Saved") }));
     try {
       const dismissToast = screen.getByTitle("notifications.dismiss");
       // The panel's last control is no longer the trap's edge: Tab carries on (natively) to the toast.
@@ -234,7 +234,7 @@ describe("Modal focus trap (offsetParent stubbed 'visible')", () => {
         <Body />
       </Modal>,
     );
-    act(() => void notify({ level: "error", message: "Nope" }));
+    act(() => void notify({ level: "error", message: raw("Nope") }));
     const dismissToast = screen.getByTitle("notifications.dismiss");
     dismissToast.focus();
     expect(document.activeElement).toBe(dismissToast); // the scenario is actually being driven
@@ -311,6 +311,100 @@ describe("Modal focus trap (offsetParent stubbed 'visible')", () => {
     document.body.removeChild(trigger);
   });
 
+  it("hands its trigger to the dialog left standing above it, which restores it on close", () => {
+    // The standing upper dialog captured ITS restore target while the focus was inside the lower
+    // one — a control that is gone once the lower closes. So the lower skipping its own restore
+    // (above) handed the trigger to no one, and closing the upper left the focus on <body>.
+    // The arrangement keyboard help or the error dialog opened over a dialog actually has.
+    const trigger = document.createElement("button");
+    document.body.appendChild(trigger);
+    trigger.focus();
+    function Siblings() {
+      const [lower, setLower] = useState(true);
+      const [upper, setUpper] = useState(false);
+      return (
+        <>
+          {lower && (
+            <Modal initialFocus="close" title="lower" onClose={() => {}}>
+              <button onClick={() => setUpper(true)}>open upper</button>
+              <button onClick={() => setLower(false)}>close lower</button>
+            </Modal>
+          )}
+          {upper && (
+            <Modal initialFocus="close" title="upper" onClose={() => {}}>
+              <button onClick={() => setUpper(false)}>close upper</button>
+            </Modal>
+          )}
+        </>
+      );
+    }
+    render(<Siblings />);
+    screen.getByText("open upper").focus();
+    act(() => void screen.getByText("open upper").click()); // opened from inside the lower dialog
+    const inUpper = screen.getByText("close upper");
+    inUpper.focus();
+    // The lower closes on its own under the standing upper (`.click()` moves no focus).
+    act(() => void screen.getByText("close lower").click());
+    expect(screen.queryByText("close lower")).toBeNull();
+    expect(document.activeElement).toBe(inUpper);
+    act(() => void inUpper.click());
+    expect(document.activeElement).toBe(trigger);
+    document.body.removeChild(trigger);
+  });
+
+  it("restores the trigger when it closes with the focus in one of its menus", () => {
+    // The popover engine portals a menu out of the dialog's root (it carries no aria-modal), so a
+    // focus on a menu row read as "the user walked away": Back with a menu open inside a dialog
+    // left the focus on <body>. The portal marker is the one `ui/AnchoredPopover` reads too.
+    const trigger = document.createElement("button");
+    document.body.appendChild(trigger);
+    trigger.focus();
+    const portal = document.createElement("div");
+    portal.setAttribute("data-floating-ui-portal", "");
+    document.body.appendChild(portal);
+    const { unmount } = render(
+      <Modal initialFocus="close" title="t" onClose={() => {}}>
+        <Body />
+        {createPortal(<button>menu-row</button>, portal)}
+      </Modal>,
+    );
+    screen.getByText("menu-row").focus();
+    unmount();
+    expect(document.activeElement).toBe(trigger);
+    document.body.removeChild(trigger);
+    document.body.removeChild(portal);
+  });
+
+  it("does not pull the focus out of a menu that stays open when it closes on its own", () => {
+    // The other side of counting a menu row as held: a menu that is NOT this dialog's — a page's
+    // "…" left open while a dialog finishes in the background — stays standing, and a dialog that
+    // closes on its own (a write's success) must not take the focus from it to its trigger.
+    const trigger = document.createElement("button");
+    document.body.appendChild(trigger);
+    trigger.focus();
+    const portal = document.createElement("div");
+    portal.setAttribute("data-floating-ui-portal", "");
+    const row = document.createElement("button");
+    row.textContent = "page-menu-row";
+    portal.appendChild(row);
+    document.body.appendChild(portal);
+    function SelfClosing() {
+      const [open, setOpen] = useState(true);
+      return open ? (
+        <Modal initialFocus="close" title="t" onClose={() => {}}>
+          <button onClick={() => setOpen(false)}>finish</button>
+        </Modal>
+      ) : null;
+    }
+    render(<SelfClosing />);
+    row.focus();
+    act(() => void screen.getByText("finish").click()); // `.click()` moves no focus
+    expect(screen.queryByText("finish")).toBeNull();
+    expect(document.activeElement).toBe(row);
+    document.body.removeChild(trigger);
+    document.body.removeChild(portal);
+  });
+
   it("leaves the focus alone when the user moved it out of the dialog themselves", () => {
     // The other half of the same rule, and the branch nothing drove: taking focus back from where
     // the user deliberately put it is the rudest thing a closing dialog can do.
@@ -361,7 +455,7 @@ describe("Modal — toasts raised while it is open", () => {
         <Body />
       </Modal>,
     );
-    act(() => void notify({ level: "error", message: "Couldn't share it." }));
+    act(() => void notify({ level: "error", message: raw("Couldn't share it.") }));
     expect(screen.getByRole("dialog").textContent).toContain("Couldn't share it.");
   });
 });

frontend/src/components/ui/Modal.tsx

@@ -65,6 +65,7 @@ export default function Modal({
   placement = "center",
   initialFocus,
   headerActions,
+  url,
 }: {
   title: ReactNode;
   initialFocus: ModalFocus;
@@ -81,10 +82,14 @@ export default function Modal({
   placement?: "center" | "drawer" | "drawer-start" | "top";
   /** Controls beside the ✕ in the header (a side panel's pin and customize, C2). */
   headerActions?: ReactNode;
+  /** What the dialog names in the address while it is open, when it is part of the view (a viewer, a
+   *  player): written into its own history entry, so a reload or a bookmark reopens it and Back lands
+   *  on the address without it (lib/history). */
+  url?: Record<string, string | null>;
 }) {
   const { t } = useTranslation();
   // Browser/mouse Back closes the topmost modal instead of navigating away.
-  useBackToClose(onClose);
+  useBackToClose(onClose, url);
   // ONE container element for the dialog's whole life, re-parented between <body> and the fullscreen
   // element — and attached before the children commit, so an `autoFocus` child
   // still gets the focus. Both rules live in the hook; `ui/AnchoredPopover` shares it.

frontend/src/components/ui/PageScroller.dom.test.tsx

@@ -17,6 +17,7 @@ vi.mock("react-i18next", async (importOriginal) => {
 import PageScroller from "./PageScroller";
 import BackToTop from "./BackToTop";
 import { notifyNav } from "../../lib/history";
+import { revealedNavItem } from "../../lib/listNav";
 
 beforeAll(() => {
   // useScrollFade wires a ResizeObserver (watch-the-children); jsdom ships none.
@@ -125,6 +126,38 @@ describe("PageScroller scroll memory", () => {
     expect(main.scrollTop).toBe(450);
   });
 
+  // Back focuses an item the restore did not expect — one that moved to another list while the page
+  // was away — and scrolls it into view: the restore's next frame put the old offset back over it.
+  it("gives the page up to an item brought into view while it restores", () => {
+    let frames: FrameRequestCallback[] = [];
+    vi.stubGlobal("requestAnimationFrame", (cb: FrameRequestCallback) => frames.push(cb));
+    const flush = (n: number) => {
+      for (let i = 0; i < n; i++) {
+        const run = frames;
+        frames = [];
+        for (const cb of run) cb(0);
+      }
+    };
+    setEntry(1);
+    const { container } = render(
+      <PageScroller scrollKey="e:k1">
+        <div id="moved" />
+      </PageScroller>,
+    );
+    const main = sizedMain(container);
+    main.scrollTop = 450;
+    fireEvent.scroll(main);
+    setEntry(2);
+    notifyNav();
+    flush(1);
+    setEntry(1);
+    notifyNav(); // Back: the restore to 450 waits for its first frame
+    main.scrollTop = 120; // the item scrolled into view
+    revealedNavItem(container.querySelector("#moved")!);
+    flush(5);
+    expect(main.scrollTop).toBe(120);
+  });
+
   // Landing at the end shows Back to top, whose spacer then brings the spot within reach.
   it("finishes the way to a spot the spacer brings within reach after it lands", () => {
     let frames: FrameRequestCallback[] = [];

frontend/src/components/ui/PageScroller.tsx

@@ -12,6 +12,7 @@ import { StickyTopProvider } from "./stickyTop";
 import { useBackToTopShown, useCornerLift } from "./backToTopState";
 import { CONTENT_ID } from "./landmarks";
 import { ensureNavId, peekNavId, subscribeNav } from "../../lib/history";
+import { NAV_REVEAL_EVENT } from "../../lib/listNav";
 
 // Saved scroll offsets, keyed by `${historyEntryId}:${scrollKey}`. The entry id ties an offset to the
 // exact history entry, so Back restores where you left it and a forward navigation (a new entry) opens
@@ -63,11 +64,15 @@ function restoreScroll(el: HTMLElement, top: number): () => void {
     el.removeEventListener("wheel", stop);
     el.removeEventListener("touchstart", stop);
     el.removeEventListener("pointerdown", stop);
+    el.removeEventListener(NAV_REVEAL_EVENT, stop);
     document.removeEventListener("keydown", stop, true);
   };
   el.addEventListener("wheel", stop, { passive: true });
   el.addEventListener("touchstart", stop, { passive: true });
   el.addEventListener("pointerdown", stop);
+  // So does an item the keyboard brought into view (`lib/listNav`): Back focusing one that is not
+  // where the restored offset shows.
+  el.addEventListener(NAV_REVEAL_EVENT, stop);
   document.addEventListener("keydown", stop, true);
   const tick = () => {
     if (cancelled) return;

frontend/src/components/ui/Tabs.tsx

@@ -10,8 +10,9 @@ import { MEDIA_CHOSEN } from "./mediaChrome";
 // Below it a side rail leaves a phone too little width for the content beside it (measured at 390 px:
 // the rail clipped its own labels and Settings → Account pushed its buttons over their text), so there
 // it is a horizontal row that scrolls. A page whose sub-tab is worth keeping persists it with
-// lib/storage's useTabPersistedState (per browser tab: Admin Users, Config, Settings, Stats):
-// a reload keeps the user where they were, and a fresh tab opens on the first sub-tab. Not every
+// lib/storage's useTabPersistedState (per browser tab: Admin Users, Config, Settings) and names it in
+// the address: a reload keeps the user where they were, a link opens its tab, and a fresh tab opens on
+// the first sub-tab. Not every
 // caller: the channel manager's view is account-wide (ChannelsProvider), and Downloads, a channel page
 // and the player settings start on their first tab each time.
 //

frontend/src/components/ui/Toaster.dom.test.tsx

@@ -14,7 +14,7 @@ vi.mock("react-i18next", async (importOriginal) => {
 });
 
 import Toaster from "./Toaster";
-import { clearAll, notify } from "../../lib/notifications";
+import { clearAll, notify, raw } from "../../lib/notifications";
 import { dockUnderToasts } from "../../lib/toastDock";
 
 afterEach(() => {
@@ -31,7 +31,7 @@ describe("Toaster — one host shows the toasts", () => {
         <Toaster />
       </div>,
     );
-    act(() => void notify({ level: "error", message: "Couldn't remove the video." }));
+    act(() => void notify({ level: "error", message: raw("Couldn't remove the video.") }));
     expect(screen.getByTestId("app").textContent).toContain("Couldn't remove the video.");
 
     const overlay = render(
@@ -54,7 +54,7 @@ describe("Toaster — one host shows the toasts", () => {
   it("lets a click through where there is no toast and nothing docked, and not where there is", () => {
     const Docked = () => <button>dock</button>;
     const stop = dockUnderToasts(Docked);
-    notify({ level: "info", message: "hello" });
+    notify({ level: "info", message: raw("hello") });
     render(<Toaster />);
     const region = document.querySelector<HTMLElement>("[data-toast-region]")!;
     // The empty part of the region (beside and above a docked control) must not swallow the page's
@@ -75,7 +75,7 @@ describe("Toaster — one host shows the toasts", () => {
         <Toaster overlay />
       </div>,
     );
-    act(() => void notify({ level: "error", message: "boom" }));
+    act(() => void notify({ level: "error", message: raw("boom") }));
     fireEvent.click(screen.getByText("boom"));
     expect(backdrop).not.toHaveBeenCalled();
   });
@@ -86,11 +86,11 @@ describe("Toaster — handing the toasts to another host", () => {
     // The new host gets them as NEW nodes: a screen reader read every one out again, an error
     // assertively, each time a player (or any dialog) opened or closed.
     render(<Toaster />);
-    act(() => void notify({ level: "error", message: "old news" }));
+    act(() => void notify({ level: "error", message: raw("old news") }));
     render(<Toaster overlay />);
     const old = screen.getByText("old news").closest(".toast-card")!;
     expect(old.getAttribute("role")).toBeNull();
-    act(() => void notify({ level: "error", message: "fresh" }));
+    act(() => void notify({ level: "error", message: raw("fresh") }));
     expect(screen.getByText("fresh").closest(".toast-card")!.getAttribute("role")).toBe("alert");
   });
 
@@ -99,8 +99,8 @@ describe("Toaster — handing the toasts to another host", () => {
     // host last showed — re-read on every render, this host's own "first" turned silent the moment
     // "second" arrived (its own screen had become the handover by then).
     render(<Toaster />);
-    act(() => void notify({ level: "error", message: "first" }));
-    act(() => void notify({ level: "error", message: "second" }));
+    act(() => void notify({ level: "error", message: raw("first") }));
+    act(() => void notify({ level: "error", message: raw("second") }));
     const card = (text: string) => screen.getByText(text).closest(".toast-card")!;
     expect(card("first").getAttribute("role")).toBe("alert");
     expect(card("second").getAttribute("role")).toBe("alert");
@@ -111,7 +111,7 @@ describe("Toaster — handing the toasts to another host", () => {
     // inserted announces them anyway. React flushes effects in the SAME task as that render, so the
     // arming has to wait for the next one — a screen reader reads the region's state after the task.
     render(<Toaster />);
-    act(() => void notify({ level: "info", message: "saved" }));
+    act(() => void notify({ level: "info", message: raw("saved") }));
     const overlay = render(<Toaster overlay />);
     const region = overlay.container.querySelector("[aria-live]")!;
     expect(region.textContent).toContain("saved"); // it took the toast over…
@@ -135,7 +135,7 @@ describe("Toaster — handing the toasts to another host", () => {
               <Toaster overlay />
               <button
                 onClick={() => {
-                  notify({ level: "success", message: "upload queued" });
+                  notify({ level: "success", message: raw("upload queued") });
                   setOpen(false);
                 }}
               >
@@ -147,7 +147,7 @@ describe("Toaster — handing the toasts to another host", () => {
       );
     }
     render(<Stage />);
-    act(() => void notify({ level: "error", message: "old news" }));
+    act(() => void notify({ level: "error", message: raw("old news") }));
     fireEvent.click(screen.getByText("upload"));
 
     const card = (text: string) => screen.getByText(text).closest(".toast-card")!;
@@ -168,7 +168,7 @@ describe("Toaster — handing the toasts to another host", () => {
         <Toaster overlay order={2} />
       </div>,
     );
-    act(() => void notify({ level: "error", message: "boom" }));
+    act(() => void notify({ level: "error", message: raw("boom") }));
     expect(screen.getByTestId("dialog").textContent).toContain("boom");
     // The player swaps its host (leaving true fullscreen) while the dialog stays open.
     player.rerender(
@@ -188,7 +188,7 @@ describe("Toaster — handing the toasts to another host", () => {
     const t0 = Date.now();
     const now = vi.spyOn(Date, "now").mockReturnValue(t0);
     render(<Toaster />);
-    act(() => void notify({ level: "info", message: "saved" }));
+    act(() => void notify({ level: "info", message: raw("saved") }));
     now.mockReturnValue(t0 + 4000);
     render(<Toaster overlay />);
     const bar = screen.getByText("saved").closest(".toast-card")!.lastElementChild as HTMLElement;
@@ -199,7 +199,7 @@ describe("Toaster — handing the toasts to another host", () => {
     // At the app's own spot (bottom-4) the stack sat on the Plex transport row and PlayerModal's
     // docked bar, above them at z-overlay, and took their clicks for as long as a toast was up.
     render(<Toaster overlay />);
-    act(() => void notify({ level: "error", message: "boom" }));
+    act(() => void notify({ level: "error", message: raw("boom") }));
     const host = hosts()[0]!.closest("[data-toast-region]")!;
     expect(host.className).toContain("bottom-24");
     expect(host.className).toContain("pointer-events-none");
@@ -218,9 +218,9 @@ describe("Toaster — a toast's actions", () => {
       () =>
         void notify({
           level: "success",
-          message: "Downloaded",
-          action: { label: "Copy link", onClick: copy },
-          secondaryAction: { label: "Open", onClick: open },
+          message: raw("Downloaded"),
+          action: { label: raw("Copy link"), onClick: copy },
+          secondaryAction: { label: raw("Open"), onClick: open },
         }),
     );
     expect(screen.getByRole("button", { name: "Copy link" })).toBeTruthy();

frontend/src/components/ui/Toaster.language.dom.test.tsx

@@ -0,0 +1,104 @@
+// @vitest-environment jsdom
+//
+// A notice is said in the reader's language when it is shown, not in the one it was raised in. The
+// text used to be translated by the caller and kept so: after a language switch every toast and every
+// row of the notification center stayed in the old language, and so did the history after a reload.
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
+import { act, cleanup, render, screen } from "@testing-library/react";
+import i18n from "../../i18n";
+import Toaster from "./Toaster";
+import { clearAll, msg, notify, raw, sayNotif } from "../../lib/notifications";
+
+beforeEach(async () => {
+  await i18n.changeLanguage("en");
+});
+afterEach(async () => {
+  cleanup();
+  act(() => clearAll());
+  await i18n.changeLanguage("en");
+});
+
+describe("a notice speaks the reader's language of the moment", () => {
+  it("a toast raised in English reads Hungarian after the switch", async () => {
+    render(<Toaster />);
+    act(() => void notify({ level: "success", message: msg("common.copy.done") }));
+    const en = i18n.getFixedT("en")("common.copy.done");
+    const hu = i18n.getFixedT("hu")("common.copy.done");
+    expect(en).not.toBe(hu);
+    expect(screen.getByText(en)).toBeTruthy();
+
+    await act(async () => void (await i18n.changeLanguage("hu")));
+    expect(screen.getByText(hu)).toBeTruthy();
+    expect(screen.queryByText(en)).toBeNull();
+  });
+
+  it("its button is said again too, beside the text it acts on", async () => {
+    render(<Toaster />);
+    act(
+      () =>
+        void notify({
+          message: msg("common.copy.done"),
+          action: { label: msg("common.undo"), onClick: () => {} },
+        }),
+    );
+    expect(screen.getByRole("button", { name: "Undo" })).toBeTruthy();
+
+    await act(async () => void (await i18n.changeLanguage("hu")));
+    expect(screen.getByRole("button", { name: "Visszavonás" })).toBeTruthy();
+    expect(screen.queryByRole("button", { name: "Undo" })).toBeNull();
+  });
+
+  it("a server refusal is said again in the language of the moment", async () => {
+    render(<Toaster />);
+    act(
+      () =>
+        void notify({
+          level: "error",
+          message: { detail: { code: "not_found", reason: "view" } },
+        }),
+    );
+    expect(screen.getByText("This view doesn't exist any more")).toBeTruthy();
+
+    await act(async () => void (await i18n.changeLanguage("hu")));
+    expect(screen.getByText("Ez a nézet már nem létezik")).toBeTruthy();
+  });
+
+  it("a value inside the text is said again too, and a number is grouped the reader's way", async () => {
+    const text = msg("settings.takeout.read", {
+      name: raw("watch-history.json"),
+      count: 12345,
+      n: { number: 12345 },
+    });
+    const en = sayNotif(text);
+    await i18n.changeLanguage("hu");
+    const hu = sayNotif(text);
+    expect(en).toContain("12,345");
+    expect(hu).not.toContain("12,345");
+    expect(hu).toContain("watch-history.json");
+    expect(hu).not.toBe(en);
+  });
+});
+
+describe("the history kept from before", () => {
+  beforeEach(() => {
+    localStorage.clear();
+    vi.resetModules();
+  });
+
+  it("shows a notice stored as text as it was stored", async () => {
+    localStorage.setItem("siftlode.owner", "5");
+    localStorage.setItem(
+      "siftlode.notifications",
+      JSON.stringify([
+        { id: 1, level: "info", title: "Old title", message: "Old text", ts: 1, read: true },
+      ]),
+    );
+    const notifications = await import("../../lib/notifications");
+    const { claimLocalData } = await import("../../lib/storage");
+    claimLocalData(5);
+    const n = notifications.getNotifications()[0]!;
+    expect(n.message).toEqual(raw("Old text"));
+    expect(n.title).toEqual(raw("Old title"));
+    expect(notifications.sayNotif(n.message)).toBe("Old text");
+  });
+});

frontend/src/components/ui/Toaster.strictmode.dom.test.tsx

@@ -23,7 +23,7 @@ vi.mock("react-i18next", async (importOriginal) => {
 
 import Toaster from "./Toaster";
 import { useOverlayOrder } from "./overlayOrder";
-import { clearAll, notify } from "../../lib/notifications";
+import { clearAll, notify, raw } from "../../lib/notifications";
 
 afterEach(() => {
   cleanup();
@@ -37,7 +37,7 @@ function Harness() {
     <>
       <button
         onClick={() => {
-          notify({ level: "success", message: "Uploaded" });
+          notify({ level: "success", message: raw("Uploaded") });
           setOpen(false); // …in the SAME handler: one batch, one commit
         }}
       >

frontend/src/components/ui/Toaster.tsx

@@ -1,7 +1,7 @@
 import { useEffect, useId, useLayoutEffect, useState, useSyncExternalStore } from "react";
 import { useTranslation } from "react-i18next";
 import { X } from "lucide-react";
-import { dismiss, getActiveToasts, subscribe } from "../../lib/notifications";
+import { dismiss, getActiveToasts, sayNotif, subscribe } from "../../lib/notifications";
 import { createStore } from "../../lib/store";
 import { useToastDock } from "../../lib/toastDock";
 import { useOverlayOrder } from "./overlayOrder";
@@ -162,9 +162,11 @@ export default function Toaster({
             >
               <Icon className={`w-5 h-5 shrink-0 mt-0.5 ${color}`} />
               <div className="min-w-0 flex-1">
-                {toast.title && <div className="text-sm font-semibold">{toast.title}</div>}
+                {toast.title && (
+                  <div className="text-sm font-semibold">{sayNotif(toast.title, t)}</div>
+                )}
                 <div className="text-sm wrap-break-word">
-                  {toast.message}
+                  {sayNotif(toast.message, t)}
                   {toast.repeat > 1 && (
                     <span className="ml-1.5 align-middle text-2xs font-semibold text-muted tabular-nums">
                       ×{toast.repeat}
@@ -174,10 +176,10 @@ export default function Toaster({
                 {(toast.action || toast.secondaryAction) && (
                   <div className="mt-1 flex flex-wrap gap-x-4">
                     {[toast.action, toast.secondaryAction].map(
-                      (action) =>
+                      (action, i) =>
                         action && (
                           <Button
-                            key={action.label}
+                            key={i}
                             variant="link"
                             onClick={() => {
                               action.onClick();
@@ -185,7 +187,7 @@ export default function Toaster({
                             }}
                             className="text-sm"
                           >
-                            {action.label}
+                            {sayNotif(action.label, t)}
                           </Button>
                         ),
                     )}

frontend/src/components/ui/copyItems.tsx

@@ -2,7 +2,7 @@ import { useTranslation } from "react-i18next";
 import { Copy, Link2 } from "lucide-react";
 
 import { copyText } from "../../lib/clipboard";
-import { notify } from "../../lib/notifications";
+import { msg, type NotifText, notify } from "../../lib/notifications";
 import { type ActionMenuItem } from "./ActionMenu";
 
 // "Copy title" and "Copy link", the two rows every object's menu ends its middle group with
@@ -17,12 +17,12 @@ type Named = "title" | "name";
 
 export function useCopyItems() {
   const { t } = useTranslation();
-  const copy = (text: string, done: string) => {
+  const copy = (text: string, done: NotifText) => {
     void copyText(text).then((ok) =>
       notify(
         ok
           ? { level: "success", message: done }
-          : { level: "error", message: t("common.copy.failed") },
+          : { level: "error", message: msg("common.copy.failed") },
       ),
     );
   };
@@ -43,7 +43,7 @@ export function useCopyItems() {
             label: t(named === "title" ? "common.copy.title" : "common.copy.name"),
             icon: <Copy className="w-4 h-4" />,
             inGesture: true,
-            onSelect: () => copy(text, t("common.copy.done")),
+            onSelect: () => copy(text, msg("common.copy.done")),
           },
         ]
       : []),
@@ -54,7 +54,7 @@ export function useCopyItems() {
             label: linkLabel ?? t("common.copy.link"),
             icon: <Link2 className="w-4 h-4" />,
             inGesture: true,
-            onSelect: () => copy(link, t("common.copy.linkDone")),
+            onSelect: () => copy(link, msg("common.copy.linkDone")),
           },
         ]
       : []),

frontend/src/components/ui/dialogFocus.ts

@@ -75,6 +75,16 @@ export function lockBodyScroll(): () => void {
   };
 }
 
+// A popover engine surface (`ui/AnchoredPopover`): portalled out of the dialog's root and carrying no
+// aria-modal, so a focus on one of a dialog's menu rows is inside the dialog all the same.
+const FLOATING = "[data-floating-ui-portal]";
+
+// Restore targets handed to a dialog left standing above one that closed (see the cleanup below):
+// that dialog's own target was captured while the focus was in the one that closed, and is gone.
+// Keyed by the standing dialog's aria-modal element; a WeakMap, so a dialog that never closes
+// through this hook leaves nothing behind.
+const handedRestore = new WeakMap<Element, HTMLElement>();
+
 /** The rest of the contract: lock the page behind, open focused, hand the focus back on close.
  *  `scopeRef` is the panel the focus should land in; `ownerRef`, when the dialog is bigger than its
  *  panel, is that whole dialog — it must be the SAME element `trapTab` is scoped to, or the two
@@ -128,6 +138,11 @@ export function useDialogChrome(
     // Today that reads the same either way (a detached owner and a null one both fail every
     // `contains` below), but the cleanup should not depend on a ref React has already let go of.
     const ownerAtOpen = ownerRef?.current ?? scope;
+    // This dialog's aria-modal element, the key a closing dialog under it hands its target by.
+    const modalAtOpen =
+      ownerAtOpen?.closest('[aria-modal="true"]') ??
+      ownerAtOpen?.querySelector('[aria-modal="true"]') ??
+      null;
     if (scope && !scope.contains(document.activeElement)) {
       const back = focusedRef.current;
       const target =
@@ -144,10 +159,12 @@ export function useDialogChrome(
       // it — and while it held the focus we read that as the user walking away. Then both closing
       // together left the focus on <body>: ours skipped the restore, and the child's own
       // `restoreTo` was already detached (passive cleanups run parent-first). Measured in jsdom,
-      // and it is the ordinary case — an error dialog raised over a dialog.
+      // and it is the ordinary case — an error dialog raised over a dialog. And one of its own
+      // menus (see FLOATING): Back with a menu open closed the dialog with the focus on a menu row.
       heldRef.current =
         (owner?.contains(active) ?? false) ||
-        (active instanceof Element && active.closest('[aria-modal="true"]') != null);
+        (active instanceof Element &&
+          (active.closest('[aria-modal="true"]') != null || active.closest(FLOATING) != null));
       // Where to put the focus back on a re-mount, though: the PANEL's own last focus. A toast is
       // gone by then, so restoring onto it would strand the focus exactly as before.
       if (scopeRef.current?.contains(document.activeElement))
@@ -172,16 +189,28 @@ export function useDialogChrome(
       // this, a dialog closing on its own (an in-flight mutation's `onSuccess`) under a modal raised
       // above it pulled the focus out of that standing dialog onto our own trigger, behind its
       // scrim — where Enter still activated it.
+      //
+      // Skipped, the trigger is handed to that standing dialog instead: ITS target was captured
+      // while the focus was in ours, so it is gone now, and it falls back to the one handed to it.
+      // A popover still standing (a menu of a dialog that stays open) is not ours to take from
+      // either, though there is no dialog to hand the trigger to.
       const owner = ownerAtOpen;
       const active = document.activeElement;
+      const target = restoreTo?.isConnected
+        ? restoreTo
+        : modalAtOpen
+          ? handedRestore.get(modalAtOpen)
+          : undefined;
       const above = active instanceof Element ? active.closest('[aria-modal="true"]') : null;
       const standingAbove =
         above !== null &&
         above.isConnected &&
         !above.contains(owner as Node | null) &&
         !(owner?.contains(above) ?? false);
-      if (heldRef.current && !standingAbove && restoreTo && restoreTo.isConnected)
-        restoreTo.focus();
+      const standingMenu = active instanceof Element && active.closest(FLOATING)?.isConnected;
+      if (!heldRef.current || !target?.isConnected) return;
+      if (standingAbove) handedRestore.set(above, target);
+      else if (!standingMenu) target.focus();
     };
   }, [restoreTo, scopeRef, ownerRef, focusScope]);
 }

frontend/src/components/ui/pressableSelectable.contract.test.ts

@@ -38,6 +38,10 @@ const PLAIN: Record<string, [number, string]> = {
   "shell/NavSidebar.tsx": [3, "the account trigger and its menu rows"],
   "features/header/PaletteLauncher.tsx": [2, "launcher controls"],
   "modules/playlists/PlaylistsRail.tsx": [1, "the load-error retry"],
+  "modules/notifications/NotificationsPanel.tsx": [
+    1,
+    "the Earlier (n) fold's heading (a disclosure: its text is its label)",
+  ],
   "modules/plex/PlexCollectionEditor.tsx": [1, "a checkbox row in a picker"],
   "modules/plex/PlexInfo.tsx": [1, "the rating filter (a number)"],
   "modules/plex/PlexPlayerSettings.tsx": [1, "the clock's date-style options"],

frontend/src/components/ui/uiI18n.contract.test.ts

@@ -19,8 +19,9 @@ const PLATFORM_NAMESPACES = new Set([
 ]);
 
 const files = readSources(__dirname, "./**/*.{ts,tsx}");
-// `t("ns.…")` and `t(\`ns.…\`)` — the namespace is everything before the first dot.
-const KEY = /\bt\(\s*["`]([A-Za-z]+)\./g;
+// `t("ns.…")` and `t(\`ns.…\`)`, and a notice's `msg("ns.…")` (the same key, said when shown) — the
+// namespace is everything before the first dot.
+const KEY = /\b(?:t|msg)\(\s*["`]([A-Za-z]+)\./g;
 
 describe("components/ui/ speaks only platform i18n namespaces", () => {
   it("names no feature namespace", () => {
@@ -37,5 +38,6 @@ describe("components/ui/ speaks only platform i18n namespaces", () => {
 
   it("sees a feature namespace when one is used", () => {
     expect([...'t("plex.loading")'.matchAll(KEY)].map((m) => m[1])).toEqual(["plex"]);
+    expect([...'msg("plex.loading")'.matchAll(KEY)].map((m) => m[1])).toEqual(["plex"]);
   });
 });

frontend/src/components/ui/useCopyFeedback.dom.test.ts

@@ -11,8 +11,12 @@ vi.mock("react-i18next", async (importOriginal) => ({
   useTranslation: () => ({ i18n: { language: "en" }, t: (key: string) => key }),
 }));
 vi.mock("../../lib/clipboard", () => ({ copyText: h.copyText }));
-vi.mock("../../lib/notifications", () => ({ notify: h.notify }));
+vi.mock("../../lib/notifications", async (importOriginal) => ({
+  ...(await importOriginal<typeof import("../../lib/notifications")>()),
+  notify: h.notify,
+}));
 
+import { msg } from "../../lib/notifications";
 import { useCopyFeedback } from "./useCopyFeedback";
 
 afterEach(() => {
@@ -27,7 +31,7 @@ describe("useCopyFeedback", () => {
     await act(() => result.current.copy("sfl_x"));
     expect(h.copyText).toHaveBeenCalledWith("sfl_x");
     expect(result.current.copied).toBe(true);
-    expect(h.notify).toHaveBeenCalledWith({ level: "success", message: "common.copy.done" });
+    expect(h.notify).toHaveBeenCalledWith({ level: "success", message: msg("common.copy.done") });
     act(() => void vi.advanceTimersByTime(2000));
     expect(result.current.copied).toBe(false);
   });
@@ -49,6 +53,6 @@ describe("useCopyFeedback", () => {
     const { result } = renderHook(() => useCopyFeedback());
     await act(() => result.current.copy("sfl_x"));
     expect(result.current.copied).toBe(false);
-    expect(h.notify).toHaveBeenCalledWith({ level: "warning", message: "common.copy.failed" });
+    expect(h.notify).toHaveBeenCalledWith({ level: "warning", message: msg("common.copy.failed") });
   });
 });

frontend/src/components/ui/useCopyFeedback.ts

@@ -1,8 +1,7 @@
 import { useEffect, useRef, useState } from "react";
-import { useTranslation } from "react-i18next";
 
 import { copyText } from "../../lib/clipboard";
-import { notify } from "../../lib/notifications";
+import { msg, notify } from "../../lib/notifications";
 
 // How long a Copy button reads "Copied" after it worked.
 const COPIED_MS = 2000;
@@ -15,7 +14,6 @@ const COPIED_MS = 2000;
  *
  *  A feature file, not `ui/`: it speaks the app's notifications (as `copyItems` does). */
 export function useCopyFeedback(): { copied: boolean; copy: (value: string) => Promise<void> } {
-  const { t } = useTranslation();
   const [copied, setCopied] = useState(false);
   // One reset at a time: a copy again within the moment starts it over, not cut short by the last.
   const timer = useRef<number | undefined>(undefined);
@@ -23,12 +21,12 @@ export function useCopyFeedback(): { copied: boolean; copy: (value: string) => P
   const copy = async (value: string) => {
     if (await copyText(value)) {
       setCopied(true);
-      notify({ level: "success", message: t("common.copy.done") });
+      notify({ level: "success", message: msg("common.copy.done") });
       window.clearTimeout(timer.current);
       timer.current = window.setTimeout(() => setCopied(false), COPIED_MS);
       return;
     }
-    notify({ level: "warning", message: t("common.copy.failed") });
+    notify({ level: "warning", message: msg("common.copy.failed") });
   };
   return { copied, copy };
 }

frontend/src/content/release-notes/en.json

@@ -1,4 +1,59 @@
 [
+  {
+    "version": "0.114.3",
+    "date": "2026-11-01",
+    "new": [],
+    "fixed": [
+      "Editing a file that is neither video nor audio now says why it can't be done, instead of a generic error."
+    ]
+  },
+  {
+    "version": "0.114.2",
+    "date": "2026-10-30",
+    "new": [],
+    "fixed": [
+      "Security: a library the sign-in relies on is updated, closing two published vulnerabilities."
+    ]
+  },
+  {
+    "version": "0.114.1",
+    "date": "2026-10-30",
+    "new": [],
+    "fixed": [
+      "Notifications follow a language switch: a notice on screen and every row in the notification center are said again in the new language, their buttons too."
+    ]
+  },
+  {
+    "version": "0.114.0",
+    "date": "2026-10-29",
+    "new": [
+      "Notifications: what asks for you comes first, then everything else as one stream, newest first. Read notices older than a week fold under Earlier, and Back returns to the row you left."
+    ],
+    "fixed": [
+      "Plex: a progress save sent just before an episode ends no longer leaves it unwatched, and a refused finish no longer sticks.",
+      "After a dialog closes, the keyboard focus returns to where it was, also inside a menu that stays open."
+    ]
+  },
+  {
+    "version": "0.113.0",
+    "date": "2026-10-28",
+    "new": [
+      "The address names what you see: tabs, list views, sorts and searches (the live YouTube search too), the YouTube player and the file viewer. A reload, a bookmark or a shared link opens the same view.",
+      "A link to a video reopens the player over its page once; Back closes it. A video the page no longer lists plays on its own and says so."
+    ],
+    "fixed": [
+      "Back and Forward step through the views as you saw them, across dialogs, players and reloads: a reload under an open player no longer leaves a Back step that does nothing.",
+      "Signed out on a Plex page, the sign-in card could show a button with no text.",
+      "The channel page's address names the channel and its own view, not the page under it.",
+      "A reload during a Plex binge reopens the episode playing now, not the one it started from."
+    ]
+  },
+  {
+    "version": "0.112.1",
+    "date": "2026-10-27",
+    "new": [],
+    "fixed": ["Security: the sign-in library is updated, closing two published vulnerabilities."]
+  },
   {
     "version": "0.112.0",
     "date": "2026-10-25",

frontend/src/content/release-notes/hu.json

@@ -1,4 +1,61 @@
 [
+  {
+    "version": "0.114.3",
+    "date": "2026-11-01",
+    "new": [],
+    "fixed": [
+      "Ha nem videó- vagy hangfájlt próbálsz szerkeszteni, az alkalmazás most megmondja, miért nem lehet, általános hibaüzenet helyett."
+    ]
+  },
+  {
+    "version": "0.114.2",
+    "date": "2026-10-30",
+    "new": [],
+    "fixed": [
+      "Biztonság: frissült egy könyvtár, amelyre a bejelentkezés épül, így két nyilvános sebezhetőség záródott be."
+    ]
+  },
+  {
+    "version": "0.114.1",
+    "date": "2026-10-30",
+    "new": [],
+    "fixed": [
+      "Az értesítések követik a nyelvváltást: a képernyőn lévő értesítés és az értesítési központ minden sora az új nyelven szól, a gombjaik is."
+    ]
+  },
+  {
+    "version": "0.114.0",
+    "date": "2026-10-29",
+    "new": [
+      "Értesítések: elöl az, ami rád vár, utána minden más egy folyamban, a legújabb elöl. Az egy hétnél régebbi olvasott értesítések a Korábbiak alá csukódnak, és a Vissza arra a sorra tér vissza, ahonnan elmentél."
+    ],
+    "fixed": [
+      "Plex: az epizód vége előtt közvetlenül elküldött mentés már nem hagyja megnézetlenül, és egy elutasított befejezés sem ragad be.",
+      "Párbeszédablak bezárása után a billentyűfókusz oda tér vissza, ahol volt, egy nyitva maradó menüben is."
+    ]
+  },
+  {
+    "version": "0.113.0",
+    "date": "2026-10-28",
+    "new": [
+      "A cím megnevezi, amit látsz: a füleket, a listanézeteket, a rendezést és a kereséseket (az élő YouTube-keresést is), a YouTube-lejátszót és a fájlnézőt. Újratöltés, könyvjelző vagy megosztott link ugyanazt a nézetet nyitja meg.",
+      "Egy videóra mutató link egyszer újranyitja a lejátszót az oldala fölött, a Vissza bezárja. Ha az oldal már nem listázza a videót, a lejátszó csak azt az egyet játssza le, és ezt jelzi is."
+    ],
+    "fixed": [
+      "A Vissza és az Előre úgy lép végig a nézeteken, ahogy láttad őket, párbeszédablakokon, lejátszókon és újratöltésen át: nyitott lejátszó alatti újratöltés után nem marad semmit sem csináló Vissza-lépés.",
+      "Plex-oldalon kijelentkezve a bejelentkező kártyán felirat nélküli gomb jelenhetett meg.",
+      "A csatornaoldal címe a csatornát és annak saját nézetét nevezi meg, nem az alatta lévő oldalt.",
+      "Plexben sorozatnézés közben az újratöltés az épp futó epizódot nyitja meg, nem azt, amelyikkel kezdted."
+    ]
+  },
+  {
+    "version": "0.112.1",
+    "date": "2026-10-27",
+    "new": [],
+    "fixed": [
+      "Biztonság: frissült a bejelentkezési könyvtár, ami két nyilvánosan ismert sérülékenységet zár be."
+    ]
+  },
   {
     "version": "0.112.0",
     "date": "2026-10-25",

frontend/src/features/channel/TagManager.tsx

@@ -4,7 +4,7 @@ import { useMutation, useQuery, useQueryClient } from "@tanstack/react-query";
 import { qk } from "../../lib/queryKeys";
 import { Plus, Trash2 } from "lucide-react";
 import { api, type Tag } from "../../lib/api";
-import { notify } from "../../lib/notifications";
+import { msg, type NotifText, notify, raw } from "../../lib/notifications";
 import { notifyActionError } from "../../lib/actionErrors";
 import { useScrollFade } from "../../lib/useScrollFade";
 import { Button } from "../../components/ui/Button";
@@ -137,22 +137,22 @@ export default function TagManager({
   });
   // A failure is said and the list refetched — a tag deleted in another tab used to fail in silence
   // (a 404 `not_found/tag` gets no global dialog) and stay listed.
-  const onFailed = (e: unknown, fallback: string) => {
+  const onFailed = (e: unknown, fallback: NotifText) => {
     notifyActionError(e, fallback);
     invalidate();
   };
   const rename = useMutation({
     mutationFn: (v: { id: number; name: string }) => api.updateTag(v.id, { name: v.name }),
     onSuccess: invalidate,
-    onError: (e) => onFailed(e, t("tagManager.renameFailed")),
+    onError: (e) => onFailed(e, msg("tagManager.renameFailed")),
   });
   const del = useMutation({
     mutationFn: (v: { id: number; name: string }) => api.deleteTag(v.id),
     onSuccess: (_d, v) => {
       invalidate();
-      notify({ level: "success", message: t("tagManager.deleted", { name: v.name }) });
+      notify({ level: "success", message: msg("tagManager.deleted", { name: raw(v.name) }) });
     },
-    onError: (e) => onFailed(e, t("tagManager.deleteFailed")),
+    onError: (e) => onFailed(e, msg("tagManager.deleteFailed")),
   });
 
   // Picking a channel from a tag's popover: close the dialog, then focus it in the manager.

frontend/src/features/comfort/comfortPin.tsx

@@ -6,7 +6,7 @@ import { Loader2, Pin, PinOff } from "lucide-react";
 import { plexLang } from "../../i18n";
 import { api, type DiscoverCard, type PinKind } from "../../lib/api";
 import { notifyActionError } from "../../lib/actionErrors";
-import { notify } from "../../lib/notifications";
+import { msg, type NotifText, notify } from "../../lib/notifications";
 import { qk } from "../../lib/queryKeys";
 import { type ActionMenuItem } from "../../components/ui/ActionMenu";
 
@@ -81,9 +81,9 @@ export interface ComfortPin {
   /** `pinIdOf` and `toggle` stay module-local until a second consumer needs them: publishing them
    *  invites the next surface to re-derive the three-state loading dance (pinned / not pinned /
    *  not known yet) that `item` already encapsulates, which is what this file exists to prevent. */
-  remove: (pinId: number, title: string) => void;
+  remove: (pinId: number, title: NotifText) => void;
   /** The pin/unpin row, ready to spread into any `ActionMenuItem[]`. Empty for a null target. */
-  item: (target: PinTarget | null, title: string) => ActionMenuItem[];
+  item: (target: PinTarget | null, title: NotifText) => ActionMenuItem[];
 }
 
 /**
@@ -134,37 +134,37 @@ export function useComfortPin(open: boolean): ComfortPin {
   }, [qc]);
 
   const add = useCallback(
-    async (target: PinTarget, title: string) => {
+    async (target: PinTarget, title: NotifText) => {
       try {
         await api.addComfortPin(target.kind, target.ref);
         // The shelf lives on another page, so without this the click has no visible consequence at
         // all from the feed — the one place a toast genuinely carries the whole feedback.
-        notify({ level: "success", message: t("home.pin.added", { title }) });
+        notify({ level: "success", message: msg("home.pin.added", { title }) });
       } catch (e) {
-        notifyActionError(e, t("home.pin.addFailed"));
+        notifyActionError(e, msg("home.pin.addFailed"));
       }
       invalidate();
     },
-    [invalidate, t],
+    [invalidate],
   );
 
   const remove = useCallback(
-    (pinId: number, title: string) => {
+    (pinId: number, title: NotifText) => {
       void (async () => {
         try {
           await api.removeComfortPin(pinId);
-          notify({ level: "success", message: t("home.pin.removed", { title }) });
+          notify({ level: "success", message: msg("home.pin.removed", { title }) });
         } catch (e) {
-          notifyActionError(e, t("home.pin.removeFailed"));
+          notifyActionError(e, msg("home.pin.removeFailed"));
         }
         invalidate();
       })();
     },
-    [invalidate, t],
+    [invalidate],
   );
 
   const toggle = useCallback(
-    (target: PinTarget, title: string) => {
+    (target: PinTarget, title: NotifText) => {
       const pinId = pinIdOf(target);
       if (pinId == null) void add(target, title);
       else remove(pinId, title);
@@ -173,7 +173,7 @@ export function useComfortPin(open: boolean): ComfortPin {
   );
 
   const item = useCallback(
-    (target: PinTarget | null, title: string): ActionMenuItem[] => {
+    (target: PinTarget | null, title: NotifText): ActionMenuItem[] => {
       if (!target) return [];
       const pinId = pinIdOf(target);
       // Still loading: an honest "we don't know yet" row rather than a confident "Pin" over

frontend/src/features/diagnostics/DebugRecorder.tsx

@@ -18,7 +18,7 @@ import {
 } from "../../lib/debugRecorder";
 import { formatDateTimeSec, formatDuration } from "../../lib/format";
 import { useLayer } from "../../lib/layerStack";
-import { notify } from "../../lib/notifications";
+import { msg, notify } from "../../lib/notifications";
 import { qk } from "../../lib/queryKeys";
 import { dockUnderToasts } from "../../lib/toastDock";
 import { useMe } from "../../lib/useMe";
@@ -73,7 +73,7 @@ export default function DebugRecorder() {
     if (!id || !until) return;
     const wait = Math.min(Date.parse(until) - Date.now(), 2 ** 31 - 1);
     const timer = window.setTimeout(() => {
-      notify({ level: "warning", message: t("recorder.pill.expired", { count: minutes ?? 0 }) });
+      notify({ level: "warning", message: msg("recorder.pill.expired", { count: minutes ?? 0 }) });
       openComposer(id);
       void qc.invalidateQueries({ queryKey: qk.me() });
     }, wait);

frontend/src/features/diagnostics/IssueComposer.tsx

@@ -6,7 +6,7 @@ import { ExternalLink, FileText, Plus, Server, X } from "lucide-react";
 import { api, type DebugScreenshot, type DebugSession, type ServerLogRow } from "../../lib/api";
 import { closeComposer } from "../../lib/debugRecorder";
 import { formatBytes, formatDateTimeSec, formatUnit } from "../../lib/format";
-import { notify } from "../../lib/notifications";
+import { msg, notify } from "../../lib/notifications";
 import { useMe } from "../../lib/useMe";
 import {
   draftSteps,
@@ -217,7 +217,7 @@ function ComposerBody({
     meta: { failTitle: "recorder.composer.sendFailed" },
     onSuccess: (r) => {
       qc.setQueryData(qk.debugSession(session.id), r.session);
-      notify({ level: "success", message: t("recorder.composer.sentOk") });
+      notify({ level: "success", message: msg("recorder.composer.sentOk") });
     },
     // A failure half-way still created the issue: show what the server now has.
     onSettled: async () => {

frontend/src/features/diagnostics/useDebugRecording.ts

@@ -1,6 +1,5 @@
 import { useCallback } from "react";
 import { useIsMutating, useMutation, useQueryClient } from "@tanstack/react-query";
-import { useTranslation } from "react-i18next";
 
 import { api, type DebugSession, type DebugSessionLevel } from "../../lib/api";
 import { notifyActionError } from "../../lib/actionErrors";
@@ -14,7 +13,7 @@ import {
 } from "../../lib/debugRecorder";
 import { flushNow, liveSession } from "../../lib/diagnostics";
 import { log } from "../../lib/log";
-import { notify } from "../../lib/notifications";
+import { msg, notify } from "../../lib/notifications";
 import { qk } from "../../lib/queryKeys";
 import { updateMeCache, useMe } from "../../lib/useMe";
 
@@ -22,7 +21,6 @@ import { updateMeCache, useMe } from "../../lib/useMe";
  *  Diagnosztika and the command palette. The session itself is `me.debug_session` — the server's
  *  answer, so a reload, another tab or the cap all show the same thing. */
 export function useDebugRecording() {
-  const { t } = useTranslation();
   const qc = useQueryClient();
   const me = useMe();
   const session = liveSession(me?.debug_session);
@@ -54,7 +52,7 @@ export function useDebugRecording() {
     meta: { failTitle: "recorder.pill.stopFailed" },
     onSuccess: (r) => {
       setSession(null);
-      notify({ level: "success", message: t("recorder.pill.stopped") });
+      notify({ level: "success", message: msg("recorder.pill.stopped") });
       openComposer(r.session.id);
     },
   });
@@ -78,7 +76,7 @@ export function useDebugRecording() {
       );
       // In the evidence too, where the step list is drafted from: which step it belongs to.
       log.info("debug.screenshot", "screenshot taken", { screenshot: r.screenshot.id });
-      notify({ level: "success", message: t("recorder.pill.shotSaved") });
+      notify({ level: "success", message: msg("recorder.pill.shotSaved") });
     },
   });
 
@@ -95,9 +93,9 @@ export function useDebugRecording() {
       const n = nextStep(sessionId);
       const text = label.trim();
       log.info("debug.step", text || `step ${n}`, { n, ...(text ? { label: text } : {}) });
-      notify({ level: "info", message: t("recorder.pill.stepMarked", { n }) });
+      notify({ level: "info", message: msg("recorder.pill.stepMarked", { n }) });
     },
-    [sessionId, t],
+    [sessionId],
   );
 
   /** Capture this tab and attach it. `hide` runs around the capture so the pill is not in the
@@ -111,7 +109,7 @@ export function useDebugRecording() {
       await new Promise((r) => requestAnimationFrame(() => requestAnimationFrame(r)));
       image = await captureTab();
     } catch (err) {
-      notifyActionError(err, t("recorder.pill.shotFailed"));
+      notifyActionError(err, msg("recorder.pill.shotFailed"));
     }
     hide(false);
     if (image) shoot.mutate({ id: session.id, image });

frontend/src/features/downloads/DownloadDialog.tsx

@@ -9,7 +9,7 @@ import { invalidateDownloads } from "../../lib/downloads";
 
 // Lazy: the full profile editor only opens from the dialog's "manage presets" affordance.
 const ProfileEditor = lazy(() => import("../../modules/settings/ProfileEditor"));
-import { notify } from "../../lib/notifications";
+import { msg, notify } from "../../lib/notifications";
 import { notifyActionError } from "../../lib/actionErrors";
 import { showInTray } from "../../lib/downloadQueue";
 import { profileName } from "../../lib/vocab";
@@ -63,15 +63,15 @@ export default function DownloadDialog({
       setLastProfile(chosen);
       notify({
         level: "success",
-        message: t("downloads.dialog.added"),
-        action: { label: t("downloads.dialog.view"), onClick: () => showInTray(job.id) },
+        message: msg("downloads.dialog.added"),
+        action: { label: msg("downloads.dialog.view"), onClick: () => showInTray(job.id) },
       });
       onClose();
     } catch (e) {
       // A quota or validation refusal (422/409) is already in the global error dialog, which the
       // reporter skips; a 403/404/429 or a lost connection is not, and used to leave the dialog
       // open with nothing said.
-      notifyActionError(e, t("errors.writeFailed.enqueueDownload"));
+      notifyActionError(e, msg("errors.writeFailed.enqueueDownload"));
       setBusy(false);
     }
   };

frontend/src/features/downloads/DownloadTray.dom.test.tsx

@@ -70,6 +70,7 @@ vi.mock("../../lib/notifications", async (importOriginal) => ({
 }));
 
 import DownloadTray from "./DownloadTray";
+import { msg, type NotifText, raw } from "../../lib/notifications";
 import { noteQueue, resetQueueWatch, showInTray } from "../../lib/downloadQueue";
 import { pushLayer, removeLayer } from "../../lib/layerStack";
 import { qk } from "../../lib/queryKeys";
@@ -199,14 +200,15 @@ describe("DownloadTray", () => {
     poll([job(1, "done")], view);
     await waitFor(() => expect(h.notify).toHaveBeenCalledTimes(1));
     const notice = h.notify.mock.calls[0]![0] as {
-      title: string;
-      message: string;
-      action: { label: string; onClick: () => void };
-      secondaryAction: { label: string; onClick: () => void };
+      title: NotifText;
+      message: NotifText;
+      action: { label: NotifText; onClick: () => void };
+      secondaryAction: { label: NotifText; onClick: () => void };
     };
-    expect(notice.title).toBe("tray.done.title:Clip 1");
-    expect(notice.message).toBe("tray.done.phone");
-    expect(notice.action.label).toBe("tray.done.copyLink");
+    expect(notice.title).toEqual(msg("tray.done.title", { title: raw("Clip 1") }));
+    expect(notice.message).toEqual(msg("tray.done.phone"));
+    expect(notice.action.label).toEqual(msg("tray.done.copyLink"));
+    expect(notice.secondaryAction.label).toEqual(msg("tray.done.open"));
     notice.action.onClick();
     expect(h.share).toHaveBeenCalled();
     notice.secondaryAction.onClick();
@@ -225,9 +227,9 @@ describe("DownloadTray", () => {
     await waitFor(() => expect(h.notify).toHaveBeenCalledTimes(1));
     poll([job(1, "done"), job(2, "done")], view);
     await waitFor(() => expect(h.notify).toHaveBeenCalledTimes(2));
-    expect(h.notify.mock.calls.map((c) => (c[0] as { title: string }).title)).toEqual([
-      "tray.done.title:Clip 1",
-      "tray.done.title:Clip 2",
+    expect(h.notify.mock.calls.map((c) => (c[0] as { title: NotifText }).title)).toEqual([
+      msg("tray.done.title", { title: raw("Clip 1") }),
+      msg("tray.done.title", { title: raw("Clip 2") }),
     ]);
   });
 
@@ -236,7 +238,9 @@ describe("DownloadTray", () => {
     const view = mount();
     poll([job(1, "done", { asset: { media_kind: "file" } as never })], view);
     await waitFor(() =>
-      expect(h.notify).toHaveBeenCalledWith(expect.objectContaining({ message: "tray.done.file" })),
+      expect(h.notify).toHaveBeenCalledWith(
+        expect.objectContaining({ message: msg("tray.done.file") }),
+      ),
     );
   });
 
@@ -257,7 +261,9 @@ describe("DownloadTray", () => {
     poll([job(1, "done", { source_key: "upload" })], view);
     await waitFor(() =>
       expect(h.notify).toHaveBeenCalledWith(
-        expect.objectContaining({ title: "tray.done.uploadedTitle:Clip 1" }),
+        expect.objectContaining({
+          title: msg("tray.done.uploadedTitle", { title: raw("Clip 1") }),
+        }),
       ),
     );
   });

frontend/src/features/downloads/DownloadTray.tsx

@@ -30,7 +30,7 @@ import {
 } from "../../lib/downloadQueue";
 import { anyBlockingLayer } from "../../lib/layerStack";
 import { focusNavItem, navItemAttrs } from "../../lib/listNav";
-import { notify } from "../../lib/notifications";
+import { msg, notify, raw } from "../../lib/notifications";
 import { qk } from "../../lib/queryKeys";
 import { LS } from "../../lib/storage";
 import { useLiveQuery } from "../../lib/useLiveQuery";
@@ -191,16 +191,16 @@ export default function DownloadTray() {
     notify({
       level: "success",
       // An upload the worker had to convert first is done here too — it was never downloaded.
-      title: t(job.source_key === "upload" ? "tray.done.uploadedTitle" : "tray.done.title", {
-        title,
+      title: msg(job.source_key === "upload" ? "tray.done.uploadedTitle" : "tray.done.title", {
+        title: raw(title),
       }),
-      message: t(job.asset?.media_kind === "file" ? "tray.done.file" : "tray.done.phone"),
+      message: msg(job.asset?.media_kind === "file" ? "tray.done.file" : "tray.done.phone"),
       action: {
-        label: t("tray.done.copyLink"),
-        onClick: () => void quickShareLink(qc, { kind: "file", id: job.id }, t),
+        label: msg("tray.done.copyLink"),
+        onClick: () => void quickShareLink(qc, { kind: "file", id: job.id }),
       },
       secondaryAction: {
-        label: t("tray.done.open"),
+        label: msg("tray.done.open"),
         onClick: () => openFile(job.id, job.folder_id),
       },
     });
@@ -298,7 +298,7 @@ export default function DownloadTray() {
         id: "copyLink",
         label: t("tray.done.copyLink"),
         icon: <Link className="w-4 h-4" />,
-        onSelect: () => void quickShareLink(qc, { kind: "file", id: job.id }, t),
+        onSelect: () => void quickShareLink(qc, { kind: "file", id: job.id }),
       },
     ]);
   const menuItems = menu.target

frontend/src/features/downloads/useDownloadActions.tsx

@@ -9,6 +9,7 @@ import { useCopyItems } from "../../components/ui/copyItems";
 import { jobTitle } from "./downloadTitle";
 import { type ActionMenuItem } from "../../components/ui/ActionMenu";
 import { menuGroups } from "../../components/ui/menuGroups";
+import { msg } from "../../lib/notifications";
 
 // A queued download's ONE action list: the row's "…", its right-click, long-press and Shift+F10. The
 // row keeps its primary action (pause / resume / retry) and its state (the error and its details) in
@@ -56,7 +57,7 @@ export function useDownloadActions() {
           ? api.resumeDownload(id)
           : api.cancelDownload(id),
     onSuccess: () => invalidateDownloads(qc),
-    onError: (e, v) => notifyActionError(e, t(`errors.writeFailed.job.${v.op}`)),
+    onError: (e, v) => notifyActionError(e, msg(`errors.writeFailed.job.${v.op}`)),
   });
 
   const confirmThen = async (title: string, body: string, action: string, fn: () => void) => {

frontend/src/features/filters/useSavedViewsStore.ts

@@ -8,6 +8,7 @@ import { notifyActionError } from "../../lib/actionErrors";
 import { ownKey } from "../../lib/storage";
 import { useConfirm } from "../../components/ui/confirmContext";
 import type { SavedViewsContext, ViewSource } from "./savedViewsContext";
+import { msg, type NotifText } from "../../lib/notifications";
 
 // Saved "smart views" serve two modules — the feed and Plex — and each owns one store of them in its
 // own folder, built on this hook. The two never switch into each other: a visit to Plex leaves the
@@ -114,7 +115,7 @@ export function useSavedViewsStore(cfg: SavedViewsConfig): SavedViewsContext {
   const isDirty = displayView != null && activeView == null;
 
   const refresh = () => void qc.invalidateQueries({ queryKey: qk.savedViews(source) });
-  async function runViewMutation(fn: () => Promise<unknown>, failMsg: string): Promise<boolean> {
+  async function runViewMutation(fn: () => Promise<unknown>, failMsg: NotifText): Promise<boolean> {
     let ok = true;
     try {
       await fn();
@@ -146,28 +147,28 @@ export function useSavedViewsStore(cfg: SavedViewsConfig): SavedViewsContext {
       if (!clean) return false;
       return runViewMutation(
         () => api.createView(clean, cfg.stripForSave(cfg.filters), source),
-        t("views.actionFailed"),
+        msg("views.actionFailed"),
       );
     },
     rename: async (id, name) => {
       const next = name.trim();
       if (!next) return false;
-      return runViewMutation(() => api.updateView(id, { name: next }), t("views.actionFailed"));
+      return runViewMutation(() => api.updateView(id, { name: next }), msg("views.actionFailed"));
     },
     updateFilters: (id, filters) =>
-      runViewMutation(() => api.updateView(id, { filters }), t("views.actionFailed")),
+      runViewMutation(() => api.updateView(id, { filters }), msg("views.actionFailed")),
     saveCurrent: async (id) => {
       const filters = cfg.stripForSave(cfg.filters);
       const ok = await runViewMutation(
         () => api.updateView(id, { filters }),
-        t("views.actionFailed"),
+        msg("views.actionFailed"),
       );
       return ok ? filters : null;
     },
     toggleDefault: (v) =>
       runViewMutation(
         () => api.updateView(v.id, { is_default: !v.is_default }),
-        t("views.actionFailed"),
+        msg("views.actionFailed"),
       ).then(() => undefined),
     remove: async (v) => {
       const ok = await confirm({
@@ -177,14 +178,14 @@ export function useSavedViewsStore(cfg: SavedViewsConfig): SavedViewsContext {
       });
       if (!ok) return false;
       if (stickyId === v.id) setStickyId(null);
-      return runViewMutation(() => api.deleteView(v.id), t("views.actionFailed"));
+      return runViewMutation(() => api.deleteView(v.id), msg("views.actionFailed"));
     },
     reorder: async (nextIds) => {
       qc.setQueryData<SavedView[]>(
         qk.savedViews(source),
         nextIds.map((id) => views.find((v) => v.id === id)!).filter(Boolean),
       );
-      await runViewMutation(() => api.reorderViews(nextIds), t("views.reorderFailed"));
+      await runViewMutation(() => api.reorderViews(nextIds), msg("views.reorderFailed"));
     },
   };
 }

frontend/src/features/navigation/NavigationProvider.dom.test.tsx

@@ -27,6 +27,8 @@ vi.mock("react-i18next", async (importOriginal) => {
 
 import { NavigationProvider } from "./NavigationProvider";
 import { useNavigation, useNavigationActions } from "./navigationContext";
+import { urlPage } from "./urlPage";
+import { channelUrl } from "../../lib/urlState";
 import { useBackToClose } from "../../lib/history";
 import { PageHeading } from "../../components/ui/Headings";
 
@@ -167,6 +169,19 @@ describe("NavigationProvider · setPage's same-page guard", () => {
     expect(window.location.search).toBe("?page=plex&keep=1");
   });
 
+  it("leaves the keys of the modules it does not list by hand behind too: Files and the feed's", () => {
+    // Each module declares its keys (`urlKeys`), and the switch clears the union of them: a key
+    // missing from a hand-kept list rode along onto the next page's entry.
+    window.history.replaceState(
+      { sfPage: "files" },
+      "",
+      "/?page=files&folder=all&item=5&q=music&sort=oldest&keep=1",
+    );
+    const { result } = render();
+    act(() => result.current.setPage("plex"));
+    expect(window.location.search).toBe("?page=plex&keep=1");
+  });
+
   it("pushes nothing when it is already that page", () => {
     const { result } = render();
     act(() => result.current.setPage("plex"));
@@ -195,6 +210,93 @@ describe("NavigationProvider · setPage's same-page guard", () => {
   });
 });
 
+describe("NavigationProvider · a link carrying another page's keys", () => {
+  it("opens with only its own page's keys: what the page does not show, its address does not say", () => {
+    window.history.replaceState(
+      {},
+      "",
+      "/?page=activity&at=logs&folder=all&ctab=hidden&q=music&pscope=movie&pl=3&keep=1",
+    );
+    render();
+    expect(window.location.search).toBe("?page=activity&at=logs&keep=1");
+  });
+
+  it("keeps the channel page open over any page", () => {
+    window.history.replaceState({}, "", "/?page=stats&chan=UC1&folder=all");
+    const { result } = render();
+    expect(window.location.search).toBe("?page=stats&chan=UC1");
+    expect(result.current.channelView?.id).toBe("UC1");
+  });
+
+  it("opens a channel link with only the channel page's keys, even over the page they belong to", () => {
+    window.history.replaceState({}, "", "/?q=music&sort=oldest&chan=UC1&chtab=about&chtypes=ns");
+    render();
+    expect(window.location.search).toBe("?chan=UC1&chtab=about&chtypes=ns&page=feed");
+  });
+});
+
+// The channel page has an address of its own (the owner, 2026-10-05): it used to take the feed's
+// filters along (`?q=music&sort=oldest&chan=…`), naming a sort the channel did not show.
+describe("NavigationProvider · the channel page's address", () => {
+  it("names only the channel; the page under it keeps its own address for Back", async () => {
+    window.history.replaceState({ sfPage: "feed" }, "", "/?q=music&sort=oldest");
+    const { result } = render();
+    act(() => result.current.openChannel("UC1", "One"));
+    expect(window.location.search).toBe("?page=feed&chan=UC1");
+    act(() => window.history.back());
+    await vi.waitFor(() => expect(result.current.channelView).toBeNull());
+    expect(window.location.search).toBe("?q=music&sort=oldest&page=feed");
+  });
+
+  it("says no page owns the address while the channel stands over it", () => {
+    window.history.replaceState({ sfPage: "plex" }, "", "/?page=plex");
+    const { result } = render();
+    expect(result.current.page).toBe("plex");
+    expect(urlPage(result.current)).toBe("plex");
+    act(() => result.current.openChannel("UC1", "One"));
+    expect(urlPage(result.current)).toBeNull();
+  });
+
+  it("another channel opened from it starts fresh", () => {
+    const { result } = render();
+    act(() => result.current.openChannel("UC1", "One"));
+    window.history.replaceState(window.history.state, "", "/?chan=UC1&chtab=about&chsort=oldest");
+    act(() => result.current.openChannel("UC2", "Two"));
+    expect(window.location.search).toBe("?chan=UC2");
+  });
+
+  it("a page switch takes the channel page's keys with it", () => {
+    window.history.replaceState({}, "", "/?chan=UC1&chtab=about&chsort=oldest&chtypes=n");
+    const { result } = render();
+    act(() => result.current.setPage("stats"));
+    expect(window.location.search).toBe("?page=stats");
+  });
+
+  it("closing it in place takes its keys with it", () => {
+    window.history.replaceState({}, "", "/?chan=UC1&chtab=about&chtypes=n");
+    const { result } = render();
+    stubNavigation([false]);
+    act(() => result.current.closeChannel());
+    expect(window.location.search).toBe("?page=feed");
+  });
+});
+
+// The YouTube player opens over any page and names itself in its own entry (lib/playerUrlState).
+describe("NavigationProvider · the player's address", () => {
+  it("a page switch takes a player the address still names with it", () => {
+    window.history.replaceState({}, "", "/?q=music&watch=v1&wrel=v2&wtab=related");
+    const { result } = render();
+    act(() => result.current.setPage("stats"));
+    expect(window.location.search).toBe("?page=stats");
+  });
+
+  it("a channel link names no player: opening the channel closes it", () => {
+    window.history.replaceState({}, "", "/?q=music&watch=v1&wrel=v2&wtab=related");
+    render();
+    expect(channelUrl("UC1")).toBe("/?page=feed&chan=UC1");
+  });
+});
+
 describe("NavigationProvider · Back", () => {
   // A tab that had a since-removed module open, reloaded onto the new build: its older history
   // entries still name that page, and Back lands on one of them.
@@ -208,7 +310,7 @@ describe("NavigationProvider · Back", () => {
     expect(result.current.page).toBe("feed");
     // …and the entry says so too, so the address bar and a later Feed click agree with the screen.
     expect(window.history.state).toMatchObject({ sfPage: "feed" });
-    expect(window.location.search).toBe("?keep=1");
+    expect(window.location.search).toBe("?page=feed&keep=1");
   });
 
   it("lands where a retired page's content went, and the entry names that page", () => {
@@ -325,7 +427,7 @@ describe("NavigationProvider · a page the account cannot open", () => {
     window.history.replaceState(null, "", "/?page=scheduler&keep=1");
     const { result } = render();
     expect(result.current.page).toBe("feed");
-    expect(window.location.search).toBe("?keep=1");
+    expect(window.location.search).toBe("?page=feed&keep=1");
     expect(window.history.state).toMatchObject({ sfPage: "feed" });
   });
 
@@ -361,7 +463,7 @@ describe("NavigationProvider · a page the account cannot open", () => {
       qc.setQueryData(qk.me(), member);
     });
     await settle();
-    expect(window.location.search).toBe("");
+    expect(window.location.search).toBe("?page=feed");
     expect(window.history.state).toMatchObject({ sfPage: "feed" });
     expect(getAccountRaw(PAGE_KEY)).toBe("feed");
     act(() => {
@@ -381,7 +483,7 @@ describe("NavigationProvider · a page the account cannot open", () => {
     });
     await settle();
     expect(result.current.channelView).toBeNull();
-    expect(window.location.search).toBe("");
+    expect(window.location.search).toBe("?page=feed");
     expect(window.history.state?._chan).toBeUndefined();
   });
 });

frontend/src/features/navigation/NavigationProvider.reloadedRewrite.dom.test.tsx

@@ -0,0 +1,57 @@
+// @vitest-environment jsdom
+//
+// A reload under a dialog that does not reopen (About) loads on the dialog's entry, its overlay mark
+// still on it. A view rewritten in place there (the search refined) is another view: the next overlay
+// pushes its own entry over it rather than taking this one over — taken over, closing it stepped back
+// onto the entry below, and the screen went back to the search before the refine. Its own file: the
+// entry is read as the history module loads, so it is set up before the import.
+import { describe, expect, it, vi } from "vitest";
+import { act, renderHook } from "@testing-library/react";
+import { QueryClient, QueryClientProvider } from "@tanstack/react-query";
+import type { ReactNode } from "react";
+
+vi.mock("react-i18next", async (importOriginal) => ({
+  ...(await importOriginal<typeof import("react-i18next")>()),
+  useTranslation: () => ({ t: (k: string) => k, i18n: { language: "en" } }),
+}));
+
+describe("a view rewritten in place on the entry a reload under a dialog started from", () => {
+  it("is where an overlay over it closes to", async () => {
+    window.history.replaceState({ sfPage: "feed", _yt: "dogs" }, "", "/?page=feed&yt=dogs");
+    window.history.pushState(
+      { sfPage: "feed", _yt: "dogs", _ov: 1, _ovd: 1 },
+      "",
+      "/?page=feed&yt=dogs",
+    );
+    const { NavigationProvider } = await import("./NavigationProvider");
+    const { useNavigation, useNavigationActions } = await import("./navigationContext");
+    const { useBackToClose } = await import("../../lib/history");
+    const { qk } = await import("../../lib/queryKeys");
+    const { claimLocalData } = await import("../../lib/storage");
+    const qc = new QueryClient();
+    qc.setQueryData(qk.me(), { id: 1, role: "admin" });
+    claimLocalData(1);
+    const wrapper = ({ children }: { children: ReactNode }) => (
+      <QueryClientProvider client={qc}>
+        <NavigationProvider>{children}</NavigationProvider>
+      </QueryClientProvider>
+    );
+    const nav = renderHook(() => ({ ...useNavigation(), ...useNavigationActions() }), { wrapper });
+    act(() => nav.result.current.enterYtSearch("cats"));
+
+    const depth = window.history.length;
+    const overlay = renderHook(() => useBackToClose(() => {}));
+    await act(async () => {
+      await Promise.resolve();
+    });
+    expect(window.history.length).toBe(depth + 1);
+
+    await act(async () => {
+      const landed = new Promise((res) => window.addEventListener("popstate", res, { once: true }));
+      overlay.unmount();
+      await landed;
+    });
+    expect(new URLSearchParams(window.location.search).get("yt")).toBe("cats");
+    expect(nav.result.current.ytSearch).toBe("cats");
+  }, 30_000); // the provider's whole import graph loads inside the case (see the header)
+});

frontend/src/features/navigation/NavigationProvider.tsx

@@ -2,8 +2,13 @@ import { useCallback, useEffect, useMemo, useState, type ReactNode } from "react
 import { useLatest } from "../../lib/useLatest";
 import { useTranslation } from "react-i18next";
 import { useMe } from "../../lib/useMe";
-import { resolvePage, retiredParams, urlWithParams, type Page } from "../../lib/urlState";
-import { ACTIVITY_KEYS } from "../../lib/activityUrlState";
+import {
+  channelUrl,
+  resolvePage,
+  retiredParams,
+  urlWithParams,
+  type Page,
+} from "../../lib/urlState";
 import { useDocumentObjectTitle } from "../../lib/documentTitle";
 import { getAccountRaw, setAccountRaw } from "../../lib/storage";
 import {
@@ -12,8 +17,17 @@ import {
   nextNavId,
   notifyNav,
   rememberNavPosition,
+  replaceView,
 } from "../../lib/history";
-import { pageTitleKey, reachablePage } from "./moduleRegistry";
+import { foreignUrlKeys, moduleUrlKeys, pageTitleKey, reachablePage } from "./moduleRegistry";
+import { CHANNEL_PAGE_KEYS } from "../../lib/channelPageUrlState";
+import { PLAYER_KEYS } from "../../lib/playerUrlState";
+import {
+  DEFAULT_YT_COUNT,
+  ytCountFrom,
+  ytSearchFrom,
+  ytSearchParams,
+} from "../../lib/ytSearchUrlState";
 import {
   channelViewFrom,
   loadInitialPage,
@@ -37,24 +51,35 @@ import {
 //
 // The contexts, their value types and the hooks live in navigationContext.ts.
 
-/** The address bar of `page`'s root: the page (feed implicit) with every view-specific key cleared. */
+/** The address bar of `page`'s root: the page — the feed too: a bare address is the landing (Home, or
+ *  the remembered page), so a feed left unnamed reloaded or bookmarked as another page — no channel or
+ *  player over it, and every module's own keys cleared — a page switch resets to that module's root,
+ *  and its store mirrors what it holds back in. */
 function pageRootParams(page: Page): Record<string, string | null> {
   return {
-    page: page === "feed" ? null : page,
-    chan: null,
-    v: null,
-    pl: null,
-    pscope: null,
-    psort: null,
-    pshow: null,
-    pf: null,
-    ctab: null,
-    csort: null,
-    cf: null,
-    ...Object.fromEntries(ACTIVITY_KEYS.map((k) => [k, null])),
+    page,
+    ...closedChannelParams(),
+    ...nulls(PLAYER_KEYS),
+    ...nulls(moduleUrlKeys()),
   };
 }
 
+/** The address of the page under a live search, the search ended: no search, player or channel. */
+const searchEndParams = (): Record<string, string | null> => ({
+  ...closedChannelParams(),
+  ...nulls(PLAYER_KEYS),
+  ...ytSearchParams(null, DEFAULT_YT_COUNT),
+});
+
+const nulls = (keys: readonly string[]) => Object.fromEntries(keys.map((k) => [k, null]));
+
+/** No channel page: neither `chan` nor its view's keys, which the page itself writes (ChannelPage) —
+ *  a closed channel leaves none behind. (An opened one gets its address from `channelUrl`.) */
+const closedChannelParams = (): Record<string, string | null> => ({
+  chan: null,
+  ...nulls(CHANNEL_PAGE_KEYS),
+});
+
 export function NavigationProvider({ children }: { children: ReactNode }) {
   const { t, i18n } = useTranslation();
   // Held here as well as in Settings: this is the instance mounted on every boot, so a value only
@@ -66,18 +91,30 @@ export function NavigationProvider({ children }: { children: ReactNode }) {
   // and the address bar (stamped from it below) agree.
   const me = useMe();
   const page = reachablePage(chosenPage, me);
-  // Ephemeral: not persisted and not in the URL, so a reload returns to the normal feed (a search
-  // spends quota, so we never auto-replay it) — UNLESS it was zero-quota scrape-sourced, which rides
-  // in history.state and is free to re-fetch. The popstate handler derives it from history.state so
-  // Back steps player → search → feed instead of the search vanishing without a history entry.
-  const [ytSearch, setYtSearch] = useState<string | null>(() => {
-    const st = window.history.state;
-    return st?._yt && st?._ytScrape ? (st._yt as string) : null;
-  });
+  // The live YouTube search: named in the address (`yt`, and `ytn` for its count, lib/ytSearchUrlState)
+  // so a reload or a link opens it again; its own history entry, so Back steps player → search → feed.
+  // Whether it RUNS by itself is not the address's to say: `ytAsked` is the term this document was
+  // asked to search for (sent from the search box, or "Search YouTube" pressed), on the entries
+  // it has stayed on since — leaving the search ends it. Anything else — a reload, a link, a Back or
+  // a Forward onto a search — runs only when it costs no quota (Feed decides).
+  const [ytSearch, setYtSearch] = useState<string | null>(() =>
+    page === "feed" ? ytSearchFrom(new URLSearchParams(window.location.search)) : null,
+  );
+  const [ytCount, setYtCountState] = useState(() =>
+    ytCountFrom(new URLSearchParams(window.location.search)),
+  );
+  const [ytAsked, setYtAsked] = useState<string | null>(null);
+  const ytSearchRef = useLatest(ytSearch);
+  const ytCountRef = useLatest(ytCount);
+  // The search ends: off the screen, and no longer asked for.
+  const endYtSearch = useCallback(() => {
+    setYtSearch(null);
+    setYtAsked(null);
+  }, []);
   // The open channel page rides in history.state (_chan = id, _chanName = a name to show before the
   // detail loads) AND is mirrored to the address bar as ?chan=<id>, so Back closes it, a reload restores
-  // it, and a bookmarked ?chan link opens it (unlike ytSearch, which is dropped). Reload of an in-app
-  // entry reads history.state._chan; a fresh bookmark has only the ?chan param.
+  // it, and a bookmarked ?chan link opens it. Reload of an in-app entry reads history.state._chan; a
+  // fresh bookmark has only the ?chan param.
   const [channelView, setChannelView] = useState<ChannelView | null>(() =>
     channelViewFrom(window.history.state, window.location.search),
   );
@@ -107,31 +144,36 @@ export function NavigationProvider({ children }: { children: ReactNode }) {
       closeOverlaysThenNavigate(() => {
         // A channel page overlays the content column, so a nav click must close it even when the
         // underlying page is unchanged (e.g. "Feed" while a channel opened from the feed).
-        if (next === pageRef.current && !channelViewRef.current) {
+        // So must a live search on it, though that press ends only the search: the page's view stays.
+        const samePage = next === pageRef.current && !channelViewRef.current;
+        if (samePage && ytSearchRef.current == null) {
           then?.();
           return;
         }
         setChannelView(null); // leave any open channel page when navigating via the rail
+        // A live search under that channel ends too: the page opens at its root, which the address
+        // below names — the Feed press over a channel opened from a search included.
+        endYtSearch();
         setPageState(next);
         setAccountRaw(PAGE_KEY, next);
         // Push an in-app history entry so browser/mouse Back steps through pages instead of leaving
         // the app. A fresh { sfPage } (no carried-over _yt/_chan markers) so each page starts at its
-        // root, and the address bar reflects the page (feed is implicit) while clearing the
-        // view-specific params (chan/v/pl and the plex content keys pscope/psort/pshow/pf) — a page
-        // switch resets to that module's root. Feed filters (owned by FeedFiltersProvider) are left
-        // intact; the plex/channels keys re-mirror from PlexProvider / ChannelsProvider on return to
-        // their page. The item it was opened from is still focused: the state setters above have not
-        // re-rendered anything yet.
+        // root, and the address bar reflects the page (the feed too) while clearing `chan` and
+        // every module's own keys (pageRootParams) — a page switch resets to that module's root, and
+        // each module's store mirrors its state back in on its page. The item it was opened from is
+        // still focused: the state setters above have not re-rendered anything yet.
+        // The press on a search over its own page ends only the search: the page's view is the one
+        // on screen and stays named — its store, unchanged, writes nothing back in.
         rememberNavPosition();
         window.history.pushState(
           { sfPage: next, sfScroll: nextNavId() },
           "",
-          urlWithParams(pageRootParams(next)),
+          urlWithParams(samePage ? searchEndParams() : pageRootParams(next)),
         );
         notifyNav();
         then?.();
       }),
-    [pageRef, channelViewRef],
+    [pageRef, channelViewRef, ytSearchRef, endYtSearch],
   );
 
   // A sub-view (channel / YT search) is an OVERLAY, not a page change. Like setPage it never lands
@@ -139,10 +181,12 @@ export function NavigationProvider({ children }: { children: ReactNode }) {
   // inside one.
   const openChannel = useCallback((id: string, name?: string) => {
     closeOverlaysThenNavigate(() => {
-      const url = urlWithParams({ chan: id });
+      // The channel's address names the channel alone: the page under it keeps its own keys on its
+      // own entry, where Back finds them, and writes none while the channel stands over it (urlPage).
+      const url = channelUrl(id);
       if (window.history.state?._chan) {
         const st = window.history.state;
-        window.history.replaceState({ ...st, _chan: id, _chanName: name ?? null }, "", url);
+        replaceView({ ...st, _chan: id, _chanName: name ?? null }, url);
       } else {
         const st = rememberNavPosition();
         window.history.pushState({ ...st, _chan: id, _chanName: name ?? null }, "", url);
@@ -157,36 +201,67 @@ export function NavigationProvider({ children }: { children: ReactNode }) {
       // No owned history entry (e.g. opened straight from a ?chan bookmark), or none of this document
       // below it to step back to (a full tab, see backStaysInDocument): clear it in place — the
       // entry's channel marks and the ?chan param.
+      // A live search under it (the channel opened from its results) is on screen again, and named
+      // again: the channel's address carried none of it.
       setChannelView(null);
       const { _chan: _id, _chanName: _name, ...st } = window.history.state ?? {};
-      window.history.replaceState(st, "", urlWithParams({ chan: null }));
+      replaceView(
+        st,
+        urlWithParams({
+          ...closedChannelParams(),
+          ...ytSearchParams(ytSearchRef.current, ytCountRef.current),
+        }),
+      );
     }
-  }, []);
+  }, [ytSearchRef, ytCountRef]);
 
   const enterYtSearch = useCallback((q: string) => {
     setYtSearch(q);
-    // Drop any prior _ytScrape marker — the new search's source isn't known yet; Feed re-stamps it
-    // once the results resolve, so a reload only restores a confirmed scrape-sourced search.
-    const { _ytScrape: _drop, ...st } = window.history.state || {};
-    if (st._yt)
-      window.history.replaceState({ ...st, _yt: q }, ""); // refine current search
-    else {
-      // New sub-view entry.
-      const { _ytScrape: _dropToo, ...left } = rememberNavPosition();
-      window.history.pushState({ ...left, sfPage: "feed", _yt: q }, "");
+    setYtAsked(q);
+    const st = window.history.state ?? {};
+    const here = new URLSearchParams(window.location.search);
+    if (st._yt || ytSearchFrom(here) != null) {
+      // Refine the search on screen, in place, at the count it shows (one a link opened too: it
+      // is the first entry of this document, so its new `_yt` mark has nothing of ours below it).
+      replaceView({ ...st, _yt: q }, urlWithParams(ytSearchParams(q, ytCountFrom(here))));
+    } else {
+      // New sub-view entry, at the default count — ours (`_ytOwn`): leaving it steps back off it.
+      setYtCountState(DEFAULT_YT_COUNT);
+      const left = rememberNavPosition();
+      window.history.pushState(
+        { ...left, sfPage: "feed", _yt: q, _ytOwn: 1 },
+        "",
+        urlWithParams(ytSearchParams(q, DEFAULT_YT_COUNT)),
+      );
     }
   }, []);
 
+  // The press that runs the search on screen, where it did not run by itself.
+  const askYtSearch = useCallback(() => setYtAsked(ytSearchRef.current), [ytSearchRef]);
+
+  const setYtCount = useCallback(
+    (n: number) => {
+      setYtCountState(n);
+      replaceView(
+        window.history.state ?? {},
+        urlWithParams(ytSearchParams(ytSearchRef.current, n)),
+      );
+    },
+    [ytSearchRef],
+  );
+
   const exitYtSearch = useCallback(() => {
     // Pop our search entry (so Forward still works); fall back to a clear in place if we don't own
-    // one, or there is no entry of this document below it (a full tab, see backStaysInDocument).
-    if (window.history.state?._yt && backStaysInDocument()) window.history.back();
+    // one — a search a link or a reload opened is marked (`_yt`) but was pushed by nobody: below it is
+    // another site, or nothing — or there is no entry of this document below it (a full tab, see
+    // backStaysInDocument).
+    if (window.history.state?._ytOwn && backStaysInDocument()) window.history.back();
     else {
-      setYtSearch(null);
-      const { _yt: _q, _ytScrape: _scrape, ...st } = window.history.state ?? {};
-      window.history.replaceState(st, "");
+      endYtSearch();
+      const { _yt: _q, _ytOwn: _own, ...st } = window.history.state ?? {};
+      replaceView(st, urlWithParams(ytSearchParams(null, DEFAULT_YT_COUNT)));
     }
-  }, []);
+  }, [endYtSearch]);
 
   // Leaving the feed ends any live YouTube search, so coming back shows the normal feed. Adjusted
   // DURING the render that changes the page, against the page we were last on: as an effect it ran
@@ -196,7 +271,7 @@ export function NavigationProvider({ children }: { children: ReactNode }) {
   const [pageSearchWasOn, setPageSearchWasOn] = useState(page);
   if (pageSearchWasOn !== page) {
     setPageSearchWasOn(page);
-    if (page !== "feed") setYtSearch(null);
+    if (page !== "feed") endYtSearch();
   }
 
   // The browser tab names the place and the object in it (DESIGN § Composition, "Where am I"):
@@ -233,25 +308,33 @@ export function NavigationProvider({ children }: { children: ReactNode }) {
   // then sync state from history.state on popstate — the browser restores each entry's URL for us, so
   // the popstate handler only needs to read history.state.
   useEffect(() => {
-    // A reload drops a stale _yt EXCEPT when scrape-sourced (zero quota): then keep _yt + _ytScrape
-    // so it restores and re-fetches free (ytSearch above already initialised from it). _chan/_chanName
-    // are always kept so a channel page survives F5.
+    // The entry of a search the address names carries its `_yt` mark, whichever way it opened (sent
+    // from the box, a reload, a link): a channel opened from its results reads the search under it
+    // from that mark. A mark left without one (an older build's entry) goes. _chan/_chanName are
+    // always kept so a channel page survives F5.
     const st = window.history.state || {};
-    // Mirror the resolved initial page to the address bar (feed implicit) so a page reached from the
-    // stored landing pref — not just from the URL — is itself bookmarkable. urlWithParams preserves any
-    // ?chan / ?v / ?pl / filter params the loaders already read.
+    // Mirror the resolved initial page to the address bar (the feed too) so a page reached from the
+    // stored landing pref — not just from the URL — is itself bookmarkable. urlWithParams keeps the
+    // shell's keys (?chan, a player's) and the page's own; other pages' go (below).
     // A retired page's link — or the remembered last page, when that is what opened — also opens its
     // part of the page that replaced it (an `at` tab).
     const linked = new URLSearchParams(window.location.search).get("page");
     const remembered = getAccountRaw(PAGE_KEY);
+    // A link can carry another page's keys (hand-edited, or written by an older build): the page
+    // opens without them, so its address names only what it shows — and a channel page open over it
+    // shows none of the page's own (an older build's channel links carried the feed's filters).
+    const shown = channelViewFrom(st, window.location.search);
     const url = urlWithParams({
+      ...nulls(shown ? moduleUrlKeys() : foreignUrlKeys(mountPage)),
       ...retiredParams(linked ?? (resolvePage(remembered) === mountPage ? remembered : null)),
-      page: mountPage === "feed" ? null : mountPage,
+      page: mountPage,
     });
-    if (st._yt && st._ytScrape) {
-      window.history.replaceState({ ...st, sfPage: mountPage }, "", url);
+    const named =
+      mountPage === "feed" ? ytSearchFrom(new URLSearchParams(window.location.search)) : null;
+    if (named != null) {
+      window.history.replaceState({ ...st, _yt: named, sfPage: mountPage }, "", url);
     } else {
-      const { _yt: _staleYt, _ytScrape: _staleScrape, ...rest } = st;
+      const { _yt: _staleYt, _ytScrape: _staleScrape, _ytOwn: _staleOwn, ...rest } = st;
       window.history.replaceState({ ...rest, sfPage: mountPage }, "", url);
     }
     function onPop(e: PopStateEvent) {
@@ -267,13 +350,22 @@ export function NavigationProvider({ children }: { children: ReactNode }) {
         window.history.replaceState(
           { ...window.history.state, sfPage: p },
           "",
-          urlWithParams({ ...retiredParams(sf), page: p === "feed" ? null : p }),
+          urlWithParams({ ...retiredParams(sf), page: p }),
         );
       setPageState(p);
       setAccountRaw(PAGE_KEY, p);
-      // The YouTube-search sub-view and the channel page ride in history.state, so Back/Forward
-      // restores or clears them to match the entry we landed on.
-      setYtSearch((e.state?._yt as string) ?? null);
+      // The YouTube search is read from the address the browser restored, so Back/Forward opens or
+      // clears it to match the entry we landed on. One landed on without it has ended: a Forward back
+      // onto it is not asked for, and an API search waits for a press.
+      // A channel page opened from its results stands over it: its entry carries the search's mark
+      // (its address does not), and the search stays under it — closing a player over that channel
+      // lands there, and is no leaving of the search.
+      const here = new URLSearchParams(window.location.search);
+      const under = e.state?._chan && typeof e.state._yt === "string" ? e.state._yt : null;
+      const landed = p === "feed" ? (ytSearchFrom(here) ?? under) : null;
+      setYtSearch(landed);
+      if (landed == null) setYtAsked(null);
+      setYtCountState(ytCountFrom(here));
       // The channel page rides in history.state._chan, with a ?chan URL fallback for a fresh bookmark
       // entry (URL-only, no _chan) — reading e.state alone would wrongly close the channel when a
       // popstate lands here (e.g. after an overlay's programmatic history.back()). channelViewFrom
@@ -285,12 +377,26 @@ export function NavigationProvider({ children }: { children: ReactNode }) {
   }, [mountPage]);
 
   const state = useMemo<NavigationState>(
-    () => ({ page, channelView, ytSearch }),
-    [page, channelView, ytSearch],
+    () => ({
+      page,
+      channelView,
+      ytSearch,
+      ytCount,
+      ytSearchAsked: ytSearch != null && ytAsked === ytSearch,
+    }),
+    [page, channelView, ytSearch, ytCount, ytAsked],
   );
   const actions = useMemo<NavigationActions>(
-    () => ({ setPage, openChannel, closeChannel, enterYtSearch, exitYtSearch }),
-    [setPage, openChannel, closeChannel, enterYtSearch, exitYtSearch],
+    () => ({
+      setPage,
+      openChannel,
+      closeChannel,
+      enterYtSearch,
+      exitYtSearch,
+      askYtSearch,
+      setYtCount,
+    }),
+    [setPage, openChannel, closeChannel, enterYtSearch, exitYtSearch, askYtSearch, setYtCount],
   );
 
   return (

frontend/src/features/navigation/NavigationProvider.ytSearch.dom.test.tsx

@@ -0,0 +1,320 @@
+// @vitest-environment jsdom
+//
+// The live YouTube search in the address: sent from the search box it gets its own entry naming the
+// term (and its count), a reload or a link opens it again, Back/Forward read it from the address the
+// browser restored — and only a search asked for in this document counts as asked (an API search
+// reopened any other way waits for a press, Feed's part).
+import { describe, it, expect, afterEach, beforeEach, vi } from "vitest";
+import { renderHook, act, cleanup } from "@testing-library/react";
+import { QueryClient, QueryClientProvider } from "@tanstack/react-query";
+import type { ReactNode } from "react";
+
+vi.mock("react-i18next", async (importOriginal) => {
+  const actual = await importOriginal<typeof import("react-i18next")>();
+  return {
+    ...actual,
+    useTranslation: () => ({ t: (k: string) => k, i18n: { language: "en" } }),
+  };
+});
+
+import { NavigationProvider } from "./NavigationProvider";
+import { useNavigation, useNavigationActions } from "./navigationContext";
+import { qk } from "../../lib/queryKeys";
+import { claimLocalData } from "../../lib/storage";
+
+let qc = new QueryClient();
+const wrapper = ({ children }: { children: ReactNode }) => (
+  <QueryClientProvider client={qc}>
+    <NavigationProvider>{children}</NavigationProvider>
+  </QueryClientProvider>
+);
+const render = () =>
+  renderHook(() => ({ ...useNavigation(), ...useNavigationActions() }), { wrapper });
+const search = () => new URLSearchParams(window.location.search);
+
+/** No entry of this document under the current one (a bookmark opened in a new tab). */
+function stubNoEntryBelow() {
+  Object.defineProperty(window, "navigation", {
+    configurable: true,
+    value: {
+      currentEntry: { index: 1 },
+      entries: () => [{ sameDocument: false }, { sameDocument: true }],
+    },
+  });
+}
+
+beforeEach(() => {
+  qc = new QueryClient();
+  qc.setQueryData(qk.me(), { id: 1, role: "admin", plex_enabled: true });
+  localStorage.clear();
+  claimLocalData(1);
+  window.history.replaceState({ sfPage: "feed" }, "", "/?page=feed&q=lofi");
+});
+afterEach(() => {
+  cleanup();
+  vi.restoreAllMocks();
+  Reflect.deleteProperty(window, "navigation");
+});
+
+describe("NavigationProvider · the YouTube search in the address", () => {
+  it("names a search sent from the box on an entry of its own, over the feed's", () => {
+    const { result } = render();
+    const depth = window.history.length;
+    act(() => result.current.enterYtSearch("lofi"));
+    expect(window.history.length).toBe(depth + 1);
+    expect(search().get("yt")).toBe("lofi");
+    expect(search().get("q")).toBe("lofi"); // the feed's own keys stay
+    expect(search().get("ytn")).toBeNull(); // the default count is left out
+    expect(result.current.ytSearch).toBe("lofi");
+    expect(result.current.ytSearchAsked).toBe(true);
+  });
+
+  it("refines the search on screen in place, at the count it shows", () => {
+    const { result } = render();
+    act(() => result.current.enterYtSearch("lofi"));
+    act(() => result.current.setYtCount(60));
+    expect(search().get("ytn")).toBe("60");
+    const depth = window.history.length;
+    act(() => result.current.enterYtSearch("lofi beats"));
+    expect(window.history.length).toBe(depth);
+    expect(search().get("yt")).toBe("lofi beats");
+    expect(search().get("ytn")).toBe("60");
+    expect(result.current.ytCount).toBe(60);
+  });
+
+  it("a new search starts at the default count", () => {
+    const { result } = render();
+    act(() => result.current.enterYtSearch("lofi"));
+    act(() => result.current.setYtCount(40));
+    stubNoEntryBelow(); // left in place, so the next search is a new entry
+    vi.spyOn(window.history, "back").mockImplementation(() => {});
+    act(() => result.current.exitYtSearch());
+    act(() => result.current.enterYtSearch("jazz"));
+    expect(result.current.ytCount).toBe(20);
+    expect(search().get("ytn")).toBeNull();
+  });
+
+  it("writes the count, and clears it back at the default", () => {
+    const { result } = render();
+    act(() => result.current.enterYtSearch("lofi"));
+    act(() => result.current.setYtCount(100));
+    expect(search().get("ytn")).toBe("100");
+    act(() => result.current.setYtCount(20));
+    expect(search().get("ytn")).toBeNull();
+  });
+
+  it("reopens the search a reload or a link names, not as asked", () => {
+    window.history.replaceState(null, "", "/?page=feed&yt=lofi&ytn=40");
+    const { result } = render();
+    expect(result.current.ytSearch).toBe("lofi");
+    expect(result.current.ytCount).toBe(40);
+    expect(result.current.ytSearchAsked).toBe(false);
+    expect(search().get("yt")).toBe("lofi"); // the mount's own stamp keeps it
+    act(() => result.current.askYtSearch());
+    expect(result.current.ytSearchAsked).toBe(true);
+  });
+
+  it("refines a search a link opened in place too, at the count it shows", () => {
+    window.history.replaceState(null, "", "/?page=feed&yt=lofi&ytn=40");
+    const { result } = render();
+    const depth = window.history.length;
+    act(() => result.current.enterYtSearch("jazz"));
+    expect(window.history.length).toBe(depth);
+    expect([search().get("yt"), search().get("ytn")]).toEqual(["jazz", "40"]);
+  });
+
+  it("Back onto an entry whose address alone names the search reopens it", () => {
+    const { result } = render();
+    window.history.replaceState({ sfPage: "feed" }, "", "/?page=feed&yt=lofi");
+    act(() => {
+      window.dispatchEvent(new PopStateEvent("popstate", { state: window.history.state }));
+    });
+    expect(result.current.ytSearch).toBe("lofi");
+  });
+
+  it("keeps the search mark of an entry the reload started from", () => {
+    window.history.replaceState({ sfPage: "feed", _yt: "lofi" }, "", "/?page=feed&yt=lofi");
+    render();
+    expect(window.history.state?._yt).toBe("lofi");
+  });
+
+  it("marks the entry of a search the address opened (a reload, a link)", () => {
+    window.history.replaceState({ sfPage: "feed" }, "", "/?page=feed&yt=lofi");
+    render();
+    expect(window.history.state?._yt).toBe("lofi");
+  });
+
+  it("drops an older build's search mark the address does not name", () => {
+    window.history.replaceState(
+      { sfPage: "feed", _yt: "lofi", _ytScrape: true },
+      "",
+      "/?page=feed",
+    );
+    const { result } = render();
+    expect(result.current.ytSearch).toBeNull();
+    expect(window.history.state?._yt).toBeUndefined();
+    expect(window.history.state?._ytScrape).toBeUndefined();
+  });
+
+  it("names no search under another page", () => {
+    window.history.replaceState(null, "", "/?page=plex&yt=lofi");
+    const { result } = render();
+    expect(result.current.page).toBe("plex");
+    expect(result.current.ytSearch).toBeNull();
+    expect(search().get("yt")).toBeNull();
+  });
+
+  it("Back/Forward read the search from the address the browser restored, not as asked", () => {
+    const { result } = render();
+    act(() => result.current.enterYtSearch("lofi"));
+    window.history.replaceState({ sfPage: "feed", _yt: "jazz" }, "", "/?page=feed&yt=jazz&ytn=60");
+    act(() => {
+      window.dispatchEvent(new PopStateEvent("popstate", { state: window.history.state }));
+    });
+    expect(result.current.ytSearch).toBe("jazz");
+    expect(result.current.ytCount).toBe(60);
+    expect(result.current.ytSearchAsked).toBe(false);
+
+    window.history.replaceState({ sfPage: "feed" }, "", "/?page=feed&q=lofi");
+    act(() => {
+      window.dispatchEvent(new PopStateEvent("popstate", { state: window.history.state }));
+    });
+    expect(result.current.ytSearch).toBeNull();
+  });
+
+  it("leaving a search with no entry of this document below clears it from the address", () => {
+    window.history.replaceState(null, "", "/?page=feed&yt=lofi&ytn=40");
+    const { result } = render();
+    stubNoEntryBelow();
+    const back = vi.spyOn(window.history, "back").mockImplementation(() => {});
+    act(() => result.current.exitYtSearch());
+    expect(back).not.toHaveBeenCalled();
+    expect(result.current.ytSearch).toBeNull();
+    expect(search().get("yt")).toBeNull();
+    expect(search().get("ytn")).toBeNull();
+  });
+
+  it("a search left by Back and reached again by Forward is not asked for", () => {
+    const { result } = render();
+    act(() => result.current.enterYtSearch("lofi"));
+    expect(result.current.ytSearchAsked).toBe(true);
+    window.history.replaceState({ sfPage: "feed" }, "", "/?page=feed&q=lofi");
+    act(() => {
+      window.dispatchEvent(new PopStateEvent("popstate", { state: window.history.state }));
+    });
+    window.history.replaceState({ sfPage: "feed", _yt: "lofi" }, "", "/?page=feed&yt=lofi");
+    act(() => {
+      window.dispatchEvent(new PopStateEvent("popstate", { state: window.history.state }));
+    });
+    expect(result.current.ytSearch).toBe("lofi");
+    expect(result.current.ytSearchAsked).toBe(false);
+  });
+
+  it("a search left in place is not asked for when it is opened again by a link", () => {
+    window.history.replaceState(null, "", "/?page=feed&yt=lofi");
+    const { result } = render();
+    act(() => result.current.askYtSearch());
+    stubNoEntryBelow();
+    act(() => result.current.exitYtSearch());
+    window.history.replaceState({ sfPage: "feed" }, "", "/?page=feed&yt=lofi");
+    act(() => {
+      window.dispatchEvent(new PopStateEvent("popstate", { state: window.history.state }));
+    });
+    expect(result.current.ytSearchAsked).toBe(false);
+  });
+
+  it("the Feed press over a channel opened from the search opens the plain feed", () => {
+    const { result } = render();
+    act(() => result.current.enterYtSearch("lofi"));
+    act(() => result.current.openChannel("UC1"));
+    act(() => result.current.setPage("feed"));
+    expect(result.current.channelView).toBeNull();
+    expect(result.current.ytSearch).toBeNull();
+    expect(search().get("yt")).toBeNull();
+  });
+
+  it("the Feed press on the search itself opens the plain feed, as over a channel", () => {
+    const { result } = render();
+    act(() => result.current.enterYtSearch("lofi"));
+    const depth = window.history.length;
+    act(() => result.current.setPage("feed"));
+    expect(result.current.ytSearch).toBeNull();
+    expect(search().get("yt")).toBeNull();
+    expect(window.history.length).toBe(depth + 1); // its own entry: Back returns to the search
+  });
+
+  it("the Feed press on the search keeps the feed's own view in the address", () => {
+    window.history.replaceState({ sfPage: "feed" }, "", "/?page=feed&show=all&sort=oldest");
+    const { result } = render();
+    act(() => result.current.enterYtSearch("lofi"));
+    act(() => result.current.setPage("feed"));
+    expect(search().get("yt")).toBeNull();
+    expect([search().get("show"), search().get("sort")]).toEqual(["all", "oldest"]);
+  });
+
+  it("a search sent from the box is left by a step back off its own entry", () => {
+    const { result } = render();
+    act(() => result.current.enterYtSearch("lofi"));
+    const back = vi.spyOn(window.history, "back").mockImplementation(() => {});
+    act(() => result.current.exitYtSearch());
+    expect(back).toHaveBeenCalledTimes(1);
+  });
+
+  it("a search a link opened is left in place, not by a step back off the document", () => {
+    window.history.replaceState(null, "", "/?page=feed&yt=lofi");
+    const { result } = render();
+    const back = vi.spyOn(window.history, "back");
+    act(() => result.current.exitYtSearch());
+    expect(back).not.toHaveBeenCalled();
+    expect(result.current.ytSearch).toBeNull();
+    expect(search().get("yt")).toBeNull();
+  });
+
+  it("a landing on a channel opened from the search (an overlay over it closing) keeps the search", () => {
+    const { result } = render();
+    act(() => result.current.enterYtSearch("lofi"));
+    act(() => result.current.openChannel("UC1"));
+    // A player over the channel closed: the step back lands on the channel's own entry.
+    act(() => {
+      window.dispatchEvent(new PopStateEvent("popstate", { state: window.history.state }));
+    });
+    expect(result.current.ytSearch).toBe("lofi");
+    expect(result.current.ytSearchAsked).toBe(true);
+    // Back off the channel: the search it stood over is still the one asked for.
+    window.history.replaceState({ sfPage: "feed", _yt: "lofi" }, "", "/?page=feed&yt=lofi");
+    act(() => {
+      window.dispatchEvent(new PopStateEvent("popstate", { state: window.history.state }));
+    });
+    expect(result.current.ytSearchAsked).toBe(true);
+  });
+
+  it("a landing on a channel opened from a search the address opened keeps the search", () => {
+    window.history.replaceState({ sfPage: "feed" }, "", "/?page=feed&yt=lofi");
+    const { result } = render();
+    act(() => result.current.openChannel("UC1"));
+    act(() => {
+      window.dispatchEvent(new PopStateEvent("popstate", { state: window.history.state }));
+    });
+    expect(result.current.ytSearch).toBe("lofi");
+  });
+
+  it("a channel closed in place over the search names the search again", () => {
+    const { result } = render();
+    act(() => result.current.enterYtSearch("lofi"));
+    act(() => result.current.setYtCount(40));
+    act(() => result.current.openChannel("UC1"));
+    expect(search().get("yt")).toBeNull();
+    stubNoEntryBelow();
+    act(() => result.current.closeChannel());
+    expect(result.current.ytSearch).toBe("lofi");
+    expect([search().get("yt"), search().get("ytn")]).toEqual(["lofi", "40"]);
+  });
+
+  it("a page switch takes the search off the address", () => {
+    const { result } = render();
+    act(() => result.current.enterYtSearch("lofi"));
+    act(() => result.current.setPage("home"));
+    expect(result.current.ytSearch).toBeNull();
+    expect(search().get("yt")).toBeNull();
+  });
+});

frontend/src/features/navigation/channelOverPage.dom.test.tsx

@@ -0,0 +1,111 @@
+// @vitest-environment jsdom
+//
+// The channel page opens over any page, and its address names the channel alone (the owner, 2026-10-05:
+// it used to carry the feed's filters, naming a sort the channel did not show). The page under it is
+// still mounted — its store lives at the root — and a change in it while the channel stands over it
+// (a background refetch, the header search) must not write its keys onto the channel's address. Closing
+// the channel brings them back. The real provider and the real stores; only the network is absent.
+import { describe, it, expect, vi, beforeEach, afterEach } from "vitest";
+import { act, cleanup, render, waitFor } from "@testing-library/react";
+import { QueryClient, QueryClientProvider } from "@tanstack/react-query";
+import { useEffect } from "react";
+
+vi.mock("react-i18next", async (importOriginal) => ({
+  ...(await importOriginal<typeof import("react-i18next")>()),
+  useTranslation: () => ({ t: (k: string) => k, i18n: { language: "en" } }),
+}));
+
+import { NavigationProvider } from "./NavigationProvider";
+import { ModuleStores } from "./ModuleStores";
+import { useNavigationActions, type NavigationActions } from "./navigationContext";
+import { useFeedFilters, useFeedFiltersActions } from "../../modules/feed";
+import { usePlexActions } from "../../modules/plex";
+import { useChannelsActions } from "../../modules/channels";
+import { useFilesActions } from "../../modules/files";
+import { usePlaylistsActions } from "../../modules/playlists";
+import { claimLocalData } from "../../lib/storage";
+
+type Probe = {
+  nav: NavigationActions;
+  change: Record<string, () => void>;
+};
+const probe: { current: Probe | null } = { current: null };
+
+function Probe() {
+  const nav = useNavigationActions();
+  const filters = useFeedFilters();
+  const { setFilters } = useFeedFiltersActions();
+  const plex = usePlexActions();
+  const channels = useChannelsActions();
+  const files = useFilesActions();
+  const playlists = usePlaylistsActions();
+  // Handed out after each render (an effect, not the render itself, may write outside it).
+  useEffect(() => {
+    probe.current = {
+      nav,
+      change: {
+        feed: () => setFilters({ ...filters, sort: "oldest" }),
+        plex: () => plex.setScope("movie"),
+        channels: () => channels.setView("hidden"),
+        files: () => files.setView({ kind: "folder", id: 3 }),
+        playlists: () => playlists.setSelectedId(5),
+        "plex search": () => plex.setQ("poirot"),
+        "channels search": () => channels.setSearch("tom"),
+        "files search": () => files.setSearch("notes"),
+        "playlists search": () => playlists.setSearch("jazz"),
+      },
+    };
+  });
+  return null;
+}
+
+// What each change above writes, once its page is what the address shows: [page, key, value]. A
+// search is written once the typing pauses.
+const WRITTEN: Record<string, [string, string, string]> = {
+  feed: ["feed", "sort", "oldest"],
+  plex: ["plex", "pscope", "movie"],
+  channels: ["channels", "ctab", "hidden"],
+  files: ["files", "folder", "3"],
+  playlists: ["playlists", "pl", "5"],
+  "plex search": ["plex", "pq", "poirot"],
+  "channels search": ["channels", "cq", "tom"],
+  "files search": ["files", "fq", "notes"],
+  "playlists search": ["playlists", "plq", "jazz"],
+};
+const PAUSE = () => new Promise((r) => setTimeout(r, 400));
+
+beforeEach(() => {
+  localStorage.clear();
+  claimLocalData(3);
+});
+afterEach(() => {
+  cleanup();
+  window.history.replaceState(null, "", "/");
+});
+
+const search = () => new URLSearchParams(window.location.search);
+
+describe.each(Object.keys(WRITTEN))("a channel page over %s", (change) => {
+  it("keeps the page's keys off its address, and they come back when it closes", async () => {
+    const [page, key, value] = WRITTEN[change]!;
+    // The page named even for the feed: a bare address opens on Home (the account's default).
+    window.history.replaceState({ sfPage: page }, "", `/?page=${page}`);
+    render(
+      <QueryClientProvider client={new QueryClient()}>
+        <NavigationProvider>
+          <ModuleStores>
+            <Probe />
+          </ModuleStores>
+        </NavigationProvider>
+      </QueryClientProvider>,
+    );
+    act(() => probe.current!.nav.openChannel("UC1", "One"));
+    act(() => probe.current!.change[change]!());
+    await act(PAUSE);
+    expect(search().get(key)).toBeNull();
+    expect(search().get("chan")).toBe("UC1");
+    act(() => probe.current!.nav.closeChannel());
+    await waitFor(() => expect(search().get("chan")).toBeNull());
+    await waitFor(() => expect(search().get(key)).toBe(value));
+  });
+});

frontend/src/features/navigation/moduleRegistry.ts

@@ -48,6 +48,21 @@ export const REGISTERED_PAGES: readonly Page[] = ALL.map((m) => m.id);
 
 const BY_ID = Object.fromEntries(ALL.map((m) => [m.id, m])) as Record<Page, ModuleDef>;
 
+// Every module's address-bar keys, and those of every module but `page`: what a page switch clears and
+// what a page opens without (NavigationProvider). Derived from the definitions, so a new module's keys
+// are cleared the day it declares them.
+const ALL_URL_KEYS: readonly string[] = ALL.flatMap((m) => m.urlKeys);
+export function moduleUrlKeys(): readonly string[] {
+  return ALL_URL_KEYS;
+}
+/** Every module's address-bar keys that carry typed text — what the client log keeps out (main.tsx). */
+export function typedUrlKeys(): readonly string[] {
+  return ALL.flatMap((m) => m.typedUrlKeys ?? []);
+}
+export function foreignUrlKeys(page: Page): readonly string[] {
+  return ALL.filter((m) => m.id !== page).flatMap((m) => m.urlKeys);
+}
+
 // Look up a module's definition by page id (every Page is covered, incl. settings).
 export function moduleDef(id: Page): ModuleDef {
   return BY_ID[id];

frontend/src/features/navigation/navigationContext.ts

@@ -1,5 +1,6 @@
 import { createContext, useContext } from "react";
 import type { Page } from "../../lib/urlState";
+import { DEFAULT_YT_COUNT } from "../../lib/ytSearchUrlState";
 import type { ChannelView } from "./navigationInit";
 
 // The navigation contexts + their hooks, split out of NavigationProvider so that file exports only
@@ -15,8 +16,13 @@ export interface NavigationState {
   page: Page;
   /** The open channel page (null = none). Overlays `page`; rides in history.state._chan. */
   channelView: ChannelView | null;
-  /** Live YouTube search term (null = normal feed). A feed sub-view; rides in history.state._yt. */
+  /** Live YouTube search term (null = normal feed). A feed sub-view, named in the address (`yt`). */
   ytSearch: string | null;
+  /** How many results the search gathers (`ytn`). */
+  ytCount: number;
+  /** The search on screen was asked for in this document (sent from the search box, or run again by
+   *  a press), not only reopened by a reload, a link or Back. An API search runs only when asked. */
+  ytSearchAsked: boolean;
 }
 
 export interface NavigationActions {
@@ -33,12 +39,17 @@ export interface NavigationActions {
   closeChannel: () => void;
   enterYtSearch: (q: string) => void;
   exitYtSearch: () => void;
+  /** Run the search on screen: the "Search YouTube" press. */
+  askYtSearch: () => void;
+  setYtCount: (n: number) => void;
 }
 
 export const NavigationStateContext = createContext<NavigationState>({
   page: "feed",
   channelView: null,
   ytSearch: null,
+  ytCount: DEFAULT_YT_COUNT,
+  ytSearchAsked: false,
 });
 export const NavigationActionsContext = createContext<NavigationActions>({
   setPage: () => {},
@@ -46,6 +57,8 @@ export const NavigationActionsContext = createContext<NavigationActions>({
   closeChannel: () => {},
   enterYtSearch: () => {},
   exitYtSearch: () => {},
+  askYtSearch: () => {},
+  setYtCount: () => {},
 });
 
 export function useNavigation(): NavigationState {

frontend/src/features/navigation/urlPage.ts

@@ -0,0 +1,9 @@
+import type { Page } from "../../lib/urlState";
+import type { NavigationState } from "./navigationContext";
+
+/** The page whose own keys the address bar carries: none while the channel page stands over it, so
+ *  every module store writes its keys (`useUrlMirror`) only while its page is what the screen shows.
+ *  A plain function beside the context, not a hook in it: the stores' tests mock that module. */
+export function urlPage(nav: Pick<NavigationState, "page" | "channelView">): Page | null {
+  return nav.channelView ? null : nav.page;
+}

frontend/src/features/player/ClipPanel.dom.test.tsx

@@ -30,10 +30,11 @@ vi.mock("../../lib/downloadQueue", () => ({ showInTray: (id: number) => showInTr
 const notifyActionError = vi.fn();
 vi.mock("../../lib/actionErrors", async (importOriginal) => {
   const actual = await importOriginal<typeof import("../../lib/actionErrors")>();
-  return { ...actual, notifyActionError: (e: unknown, t: string) => notifyActionError(e, t) };
+  return { ...actual, notifyActionError: (e: unknown, t: NotifText) => notifyActionError(e, t) };
 });
 
 import ClipPanel, { type ClipCrop, type ClipSource } from "./ClipPanel";
+import { msg, type NotifText } from "../../lib/notifications";
 
 afterEach(() => {
   cleanup();
@@ -188,7 +189,7 @@ describe("ClipPanel", () => {
       display_name: "The bit",
     });
     expect(notify).toHaveBeenCalledWith(
-      expect.objectContaining({ level: "success", message: "clip.queued" }),
+      expect.objectContaining({ level: "success", message: msg("clip.queued") }),
     );
     // Its View opens the tray on the new clip.
     (
@@ -214,7 +215,7 @@ describe("ClipPanel", () => {
     fireEvent.click(screen.getByRole("button", { name: "clip.cut" }));
     await waitFor(() => expect(notifyActionError).toHaveBeenCalledTimes(1));
     expect(notifyActionError.mock.calls[0]![0]).toBe(err);
-    expect(notifyActionError.mock.calls[0]![1]).toBe("clip.failed");
+    expect(notifyActionError.mock.calls[0]![1]).toEqual(msg("clip.failed"));
     expect(onClose).not.toHaveBeenCalled();
     expect((screen.getByRole("button", { name: "clip.cut" }) as HTMLButtonElement).disabled).toBe(
       false,

frontend/src/features/player/ClipPanel.tsx

@@ -5,7 +5,7 @@ import { Crop, Crosshair, Maximize, Minus, Plus, Repeat, Scissors, X } from "luc
 import { api, type ClipRequest } from "../../lib/api";
 import { DISPLAY_NAME_MAX } from "../../lib/api/downloads";
 import { invalidateDownloads } from "../../lib/downloads";
-import { notify } from "../../lib/notifications";
+import { msg, notify } from "../../lib/notifications";
 import { notifyActionError } from "../../lib/actionErrors";
 import { showInTray } from "../../lib/downloadQueue";
 import { log } from "../../lib/log";
@@ -197,14 +197,14 @@ export default function ClipPanel({
       log.info("clip.queued", "clip queued", { source: src.source, seconds: Math.round(length) });
       notify({
         level: "success",
-        message: t("clip.queued"),
-        action: { label: t("clip.view"), onClick: () => showInTray(job.id) },
+        message: msg("clip.queued"),
+        action: { label: msg("clip.view"), onClick: () => showInTray(job.id) },
       });
       onClose();
     } catch (err) {
       // A refusal the server explains (too long, quota) is already in the error dialog; a lost
       // connection or a 404 is not, and must not leave the panel looking as if nothing happened.
-      notifyActionError(err, t("clip.failed"));
+      notifyActionError(err, msg("clip.failed"));
       setBusy(false);
     }
   };

frontend/src/features/player/LinkedPlayer.tsx

@@ -0,0 +1,39 @@
+import { lazy, Suspense, useState } from "react";
+import { useQueryClient } from "@tanstack/react-query";
+import { type Video, type VideoStatus } from "../../lib/api";
+import { qk } from "../../lib/queryKeys";
+import { notifyActionError } from "../../lib/actionErrors";
+import { useStableCallback } from "../../lib/useLatest";
+import { writeVideoState } from "../video/videoWrites";
+import { useOpenLinkedPlayer } from "./useOpenLinkedPlayer";
+import { msg } from "../../lib/notifications";
+
+const PlayerModal = lazy(() => import("./PlayerModal"));
+
+/** The shell's player, for an address that names one over a page that hosts none of its own (the
+ *  channel manager, where the watched-videos dialog played it; any page a link names): the video
+ *  alone. Decided at boot, once — `hosted` is whether the page on screen then opens it itself. */
+export function LinkedPlayer({ hosted }: { hosted: boolean }) {
+  const qc = useQueryClient();
+  const [own] = useState(!hosted);
+  const [video, setVideo] = useState<Video | null>(null);
+  useOpenLinkedPlayer(
+    own,
+    () => undefined,
+    (v) => setVideo(v),
+  );
+  const onState = useStableCallback((id: string, status: VideoStatus) => {
+    const write = writeVideoState(qc, id, status);
+    write
+      .then(() => qc.invalidateQueries({ queryKey: qk.feed() }))
+      .catch((e: unknown) => notifyActionError(e, msg("errors.writeFailed.videoState")));
+    return write;
+  });
+  const close = useStableCallback(() => setVideo(null));
+  if (!video) return null;
+  return (
+    <Suspense fallback={null}>
+      <PlayerModal video={video} startAt={null} onClose={close} onState={onState} />
+    </Suspense>
+  );
+}

frontend/src/features/player/PlayerModal.dom.test.tsx

@@ -40,7 +40,7 @@ import { closeKeyboardHelp, toggleKeyboardHelp } from "../../lib/keymap";
 import { ConfirmProvider } from "../../components/ui/ConfirmProvider";
 import { useConfirm } from "../../components/ui/confirmContext";
 import { api, type Me, type Video, type VideoStatus } from "../../lib/api";
-import { clearAll, notify } from "../../lib/notifications";
+import { clearAll, notify, raw } from "../../lib/notifications";
 import { qk } from "../../lib/queryKeys";
 import { writeVideoState } from "../video/videoWrites";
 
@@ -111,6 +111,7 @@ function renderModal(ui: ReactNode) {
 afterEach(() => {
   cleanup();
   vi.restoreAllMocks();
+  window.history.replaceState(null, "", "/");
   started.length = 0;
   loaded.length = 0;
   seeks.length = 0;
@@ -313,7 +314,7 @@ describe("PlayerModal — toasts raised while it is open", () => {
         onState={() => Promise.resolve()}
       />,
     );
-    act(() => void notify({ level: "error", message: "Couldn't remove the video." }));
+    act(() => void notify({ level: "error", message: raw("Couldn't remove the video.") }));
     expect(screen.getByTestId("player-modal").textContent).toContain("Couldn't remove the video.");
   });
 
@@ -335,7 +336,7 @@ describe("PlayerModal — toasts raised while it is open", () => {
     Object.defineProperty(document, "fullscreenElement", { configurable: true, get: () => stage });
     try {
       act(() => void document.dispatchEvent(new Event("fullscreenchange")));
-      act(() => void notify({ level: "error", message: "Connection lost" }));
+      act(() => void notify({ level: "error", message: raw("Connection lost") }));
       await waitFor(() => expect(stage.textContent).toContain("Connection lost"));
     } finally {
       delete (document as { fullscreenElement?: unknown }).fullscreenElement;

frontend/src/features/player/PlayerModal.tsx

@@ -68,6 +68,7 @@ import {
 import { canFullscreenElements, fullscreenElement } from "../../lib/fullscreen";
 import { dispatch, isActivationTarget, setScopeCoveredProbe, useKeyScope } from "../../lib/keymap";
 import { useBackToClose } from "../../lib/history";
+import { linkedPlayer, playerParamUpdates, type PlayerPanelTab } from "../../lib/playerUrlState";
 import ChannelNameLink from "../video/ChannelNameLink";
 import Toaster from "../../components/ui/Toaster";
 import { useOverlayOrder } from "../../components/ui/overlayOrder";
@@ -222,8 +223,6 @@ export default function PlayerModal({
   const { openChannel } = useNavigationActions();
   const qc = useQueryClient();
   const { ref: descFadeRef, style: descFadeStyle } = useScrollFade();
-  // Browser/mouse Back closes the player instead of leaving the page.
-  useBackToClose(onClose);
   // Freeze the launch queue: the player steps through the SAME filtered + sorted list it was
   // opened with, for its whole session. The live feed refetches and reorders/drops items under
   // us — e.g. auto-marking each video watched near its end removes it from a filtered feed — which
@@ -277,6 +276,25 @@ export default function PlayerModal({
     setRelatedOf(active.id);
     setRelated(null);
   }
+  // An address that names the item this player opens on (a reload, a bookmark) names its view too: the
+  // related video playing in place over it and the panel's tab come back with it. Read once.
+  const [linked] = useState(() => {
+    const here = linkedPlayer();
+    return here && here.watch === video.id ? here : null;
+  });
+  const linkedRelated = useQuery({
+    queryKey: qk.videoRow(linked?.related ?? ""),
+    queryFn: () => api.videoRow(linked!.related!),
+    enabled: !!linked?.related,
+    retry: false,
+  });
+  const [relatedAdopted, setRelatedAdopted] = useState(false);
+  if (!relatedAdopted && linkedRelated.data) {
+    setRelatedAdopted(true);
+    // Only over the item it was named with: a step of the queue before it arrived left that one.
+    if (active.id === linked?.watch && !related)
+      setRelated({ video: linkedRelated.data, startAt: null });
+  }
   const subject = related?.video ?? active;
   const subjectResume = related
     ? (related.startAt ?? related.video.position_seconds ?? 0)
@@ -753,7 +771,7 @@ export default function PlayerModal({
   // take the side panel's place of the description, a tab beside it; stacked, a drawer over the video
   // opened from a button beside the ⓘ. The list is the OPENED video's: one played from it leaves the
   // list in place, to try the next one (the owner's pick).
-  const [panelTab, setPanelTab] = useState<"description" | "related">("description");
+  const [panelTab, setPanelTab] = useState<PlayerPanelTab>(linked?.panel ?? "description");
   const [relatedOpen, setRelatedOpen] = useState(false);
   // The drawer is the stacked layout's: going wide while it is open, the list moves into the panel's
   // tab instead. Left open, it reopened unasked when the window narrowed again.
@@ -762,6 +780,17 @@ export default function PlayerModal({
     setPanelTab("related");
   }
   const panelTabs = useTabPanel();
+  // Browser/mouse Back closes the player instead of leaving the page. Its entry's address names what
+  // it plays (the queue's item, a related one over it) and the wide panel's tab, so a reload or a
+  // bookmark reopens it as it is; the page's own entry under it never carries them.
+  useBackToClose(
+    onClose,
+    playerParamUpdates({
+      watch: active.id,
+      related: related?.video.id ?? null,
+      panel: wide ? panelTab : "description",
+    }),
+  );
   // Turned off on this instance (a daily limit of 0): no tab, no button — nothing that could only
   // be refused.
   const relatedOn = useMe().related_enabled;

frontend/src/features/player/PlayerModal.url.dom.test.tsx

@@ -0,0 +1,196 @@
+// @vitest-environment jsdom
+//
+// The URL is the view: the YouTube player names what it plays in its own history entry — the item of
+// the queue, a related video played in place over it, the wide panel's tab — so a reload or a bookmark
+// reopens it as it was, and Back lands on the page's address without it. Its own file: the overlay
+// history is module state, and these read the address the closed players of other tests step back over.
+//
+// `window.YT` is a fake installed before the player's API loader first runs (see PlayerModal.dom.test).
+import { afterEach, beforeAll, beforeEach, describe, expect, it, vi } from "vitest";
+import { act, fireEvent, render, screen, waitFor } from "@testing-library/react";
+import { QueryClient, QueryClientProvider } from "@tanstack/react-query";
+
+vi.mock("react-i18next", async (importOriginal) => ({
+  ...(await importOriginal<typeof import("react-i18next")>()),
+  useTranslation: () => ({ t: (k: string) => k, i18n: { language: "en" } }),
+}));
+vi.mock("../navigation/navigationContext", () => ({
+  useNavigationActions: () => ({ openChannel: vi.fn() }),
+}));
+vi.mock("../video/AddToPlaylist", () => ({ default: () => null }));
+vi.mock("../downloads/DownloadButton", () => ({ default: () => null }));
+
+import PlayerModal from "./PlayerModal";
+import { api, type Me, type Video } from "../../lib/api";
+import { qk } from "../../lib/queryKeys";
+
+beforeAll(() => {
+  class Stub {
+    observe() {}
+    unobserve() {}
+    disconnect() {}
+    takeRecords() {
+      return [];
+    }
+  }
+  globalThis.ResizeObserver ??= Stub as unknown as typeof ResizeObserver;
+  globalThis.IntersectionObserver ??= Stub as unknown as typeof IntersectionObserver;
+});
+
+const started: { videoId: string; start: number | undefined }[] = [];
+let playerEvents: { onReady?: () => void } = {};
+const fakePlayer = new Proxy(
+  { getCurrentTime: () => 0, getDuration: () => 3000, getVideoData: () => null },
+  { get: (t, k) => (k in t ? t[k as keyof typeof t] : k === "then" ? undefined : () => undefined) },
+);
+window.YT = {
+  Player: function (
+    _el: unknown,
+    opts: { videoId: string; playerVars: { start?: number }; events?: typeof playerEvents },
+  ) {
+    started.push({ videoId: opts.videoId, start: opts.playerVars.start });
+    playerEvents = opts.events ?? {};
+    return fakePlayer;
+  } as never,
+};
+const lastStart = () => started[started.length - 1];
+
+const vid = (id: string, position_seconds = 0): Video =>
+  ({
+    id,
+    title: `Video ${id}`,
+    channel_id: "UCx",
+    channel_title: "Channel",
+    status: "new",
+    position_seconds,
+    duration_seconds: 3000,
+    watch_url: `https://www.youtube.com/watch?v=${id}`,
+  }) as unknown as Video;
+const related = (id: string, position_seconds = 0) => ({
+  ...vid(id, position_seconds),
+  followed: false,
+});
+
+// The wide layout (the side panel with its tabs): jsdom has no matchMedia, so one is put in.
+function wideWindow() {
+  window.matchMedia = ((q: string) => ({
+    matches: q === "(min-width: 1280px)",
+    media: q,
+    addEventListener: () => {},
+    removeEventListener: () => {},
+  })) as unknown as typeof window.matchMedia;
+}
+
+function renderModal(video: Video, queue: Video[]) {
+  const qc = new QueryClient({ defaultOptions: { queries: { retry: false } } });
+  qc.setQueryData(qk.me(), { related_enabled: true } as Me);
+  return render(
+    <QueryClientProvider client={qc}>
+      <PlayerModal
+        video={video}
+        queue={queue}
+        onClose={() => {}}
+        onState={() => Promise.resolve()}
+      />
+    </QueryClientProvider>,
+  );
+}
+
+// A closed player steps back over its entry a task later (jsdom's back(), like a browser's).
+async function closeAndLand(unmount: () => void) {
+  const landed = new Promise((r) => window.addEventListener("popstate", r, { once: true }));
+  unmount();
+  await act(() => landed);
+}
+
+const here = () => new URLSearchParams(window.location.search);
+
+beforeEach(() => {
+  vi.spyOn(api, "videoDetail").mockReturnValue(new Promise(() => {}));
+  vi.spyOn(api, "related").mockResolvedValue({
+    items: [related("rel1"), related("rel2", 120)],
+    has_more: false,
+    next_cursor: null,
+  });
+});
+afterEach(() => {
+  vi.restoreAllMocks();
+  delete (window as { matchMedia?: unknown }).matchMedia;
+  started.length = 0;
+});
+
+describe("the player's address", () => {
+  it("names the item playing now in its own entry, a step of the queue too", async () => {
+    window.history.replaceState({ sfPage: "feed" }, "", "/?q=talks");
+    const r = renderModal(vid("A"), [vid("A"), vid("B")]);
+    await waitFor(() => expect(here().get("watch")).toBe("A"));
+    expect(here().get("q")).toBe("talks");
+    fireEvent.click(screen.getAllByRole("button", { name: "player.next" })[0]!);
+    await waitFor(() => expect(here().get("watch")).toBe("B"));
+    await closeAndLand(r.unmount);
+    expect(window.location.search).toBe("?q=talks");
+  });
+
+  it("wide: names the related video playing over it and the panel's tab, and Back drops it", async () => {
+    wideWindow();
+    window.history.replaceState({ sfPage: "feed" }, "", "/");
+    const r = renderModal(vid("A", 40), [vid("A", 40)]);
+    act(() => playerEvents.onReady?.());
+    fireEvent.click(screen.getByRole("tab", { name: "player.related.title" }));
+    await waitFor(() => expect(here().get("wtab")).toBe("related"));
+    const rows = await screen.findAllByRole("link", { name: "Video rel2" });
+    fireEvent.click(rows.find((a) => a.hasAttribute("data-nav-open"))!);
+    await waitFor(() => expect(here().get("wrel")).toBe("rel2"));
+    expect(here().get("watch")).toBe("A");
+    fireEvent.click(screen.getByRole("button", { name: "player.back" }));
+    await waitFor(() => expect(here().has("wrel")).toBe(false));
+    expect(here().get("watch")).toBe("A");
+    await closeAndLand(r.unmount);
+    expect(window.location.search).toBe("");
+  });
+
+  it("wide: a link's related video and panel tab come back over the item it names", async () => {
+    wideWindow();
+    window.history.replaceState({ sfPage: "feed" }, "", "/?watch=A&wrel=rel2&wtab=related");
+    const row = vi.spyOn(api, "videoRow").mockResolvedValue(vid("rel2", 120));
+    const r = renderModal(vid("A", 40), [vid("A", 40)]);
+    await waitFor(() => expect(lastStart()).toEqual({ videoId: "rel2", start: 120 }));
+    expect(row).toHaveBeenCalledWith("rel2");
+    const tab = screen.getByRole("tab", { name: "player.related.title" });
+    expect(tab.getAttribute("aria-selected")).toBe("true");
+    expect(screen.getByRole("button", { name: "player.back" })).toBeTruthy();
+    expect(here().get("wrel")).toBe("rel2");
+    await closeAndLand(r.unmount);
+    // The entry the link opened at named the player; once the player is gone, so is its name.
+    expect(window.location.search).toBe("");
+  });
+
+  it("a link's related video that arrives after the queue stepped on stays off the next item", async () => {
+    window.history.replaceState({ sfPage: "feed" }, "", "/?watch=A&wrel=rel2");
+    let arrive: (v: Video) => void = () => {};
+    vi.spyOn(api, "videoRow").mockReturnValue(new Promise<Video>((r) => (arrive = r)));
+    const r = renderModal(vid("A"), [vid("A"), vid("B")]);
+    fireEvent.click(screen.getAllByRole("button", { name: "player.next" })[0]!);
+    await waitFor(() => expect(here().get("watch")).toBe("B"));
+    await act(async () => {
+      arrive(vid("rel2", 120));
+      await new Promise((r) => setTimeout(r, 50)); // the query hands its answer on a tick later
+    });
+    expect(screen.getByRole("heading", { name: "Video B" })).toBeTruthy();
+    expect(here().has("wrel")).toBe(false);
+    await closeAndLand(r.unmount);
+  });
+
+  it("wide: a link naming another item brings none of its view", async () => {
+    wideWindow();
+    window.history.replaceState({ sfPage: "feed" }, "", "/?watch=Z&wrel=rel2&wtab=related");
+    const row = vi.spyOn(api, "videoRow").mockResolvedValue(vid("rel2", 120));
+    const r = renderModal(vid("A", 40), [vid("A", 40)]);
+    await waitFor(() => expect(here().get("watch")).toBe("A"));
+    expect(row).not.toHaveBeenCalled();
+    expect(here().has("wrel")).toBe(false);
+    expect(here().has("wtab")).toBe(false);
+    expect(lastStart()?.videoId).toBe("A");
+    await closeAndLand(r.unmount);
+  });
+});

frontend/src/features/player/RelatedVideos.tsx

@@ -26,6 +26,7 @@ import VideoCard from "../video/VideoCard";
 import { VideoMenu } from "../video/VideoMenu";
 import { announceVideoState } from "../video/stateNotice";
 import { writeVideoState, writeWatchLater } from "../video/videoWrites";
+import { msg } from "../../lib/notifications";
 
 /** Which list YouTube fills in — on the video's topic or with what trends in Hungary — is a mood,
  *  decided at the list, and the account keeps the last one (the owner's pick). */
@@ -100,7 +101,7 @@ export function RelatedVideos({
         announceVideoState(id, status, v, () => onState(id, "new"));
       })
       .catch((e: unknown) => {
-        notifyActionError(e, t("errors.writeFailed.videoState"));
+        notifyActionError(e, msg("errors.writeFailed.videoState"));
         settle(seq);
       });
   };
@@ -118,7 +119,7 @@ export function RelatedVideos({
       .catch((e: unknown) => {
         notifyActionError(
           e,
-          t(saved ? "errors.writeFailed.watchLaterAdd" : "errors.writeFailed.watchLaterRemove"),
+          msg(saved ? "errors.writeFailed.watchLaterAdd" : "errors.writeFailed.watchLaterRemove"),
         );
         settle(seq);
       });

frontend/src/features/player/useOpenLinkedPlayer.dom.test.tsx

@@ -0,0 +1,182 @@
+// @vitest-environment jsdom
+//
+// A reload or a bookmark of the YouTube player reopens it: the page that hosts it opens it once its list
+// is in — from the list, so it plays on through it, or alone from the catalog — and a page that hosts
+// none gets the shell's, the video alone. A video the catalog no longer has is said, not swallowed.
+import { afterEach, describe, expect, it, vi } from "vitest";
+import { cleanup, render, renderHook, screen, waitFor } from "@testing-library/react";
+import { QueryClient, QueryClientProvider } from "@tanstack/react-query";
+import type { ReactNode } from "react";
+
+vi.mock("react-i18next", async (importOriginal) => ({
+  ...(await importOriginal<typeof import("react-i18next")>()),
+  useTranslation: () => ({ t: (k: string) => k, i18n: { language: "en" } }),
+}));
+vi.mock("../../lib/actionErrors", () => ({ notifyActionError: vi.fn() }));
+// The player itself is not what is under test: it shows what it was opened on.
+vi.mock("./PlayerModal", () => ({
+  default: ({ video, queue }: { video: Video; queue?: Video[] }) => (
+    <p>
+      playing {video.id} {queue ? "in a list" : "alone"}
+    </p>
+  ),
+}));
+
+import { useOpenLinkedPlayer } from "./useOpenLinkedPlayer";
+import { LinkedPlayer } from "./LinkedPlayer";
+import { api, type Video } from "../../lib/api";
+import { notifyActionError } from "../../lib/actionErrors";
+import { msg } from "../../lib/notifications";
+import { qk } from "../../lib/queryKeys";
+
+const vid = (id: string) => ({ id, title: id }) as unknown as Video;
+
+function wrapper({ children }: { children: ReactNode }) {
+  const qc = new QueryClient({ defaultOptions: { queries: { retry: false } } });
+  return <QueryClientProvider client={qc}>{children}</QueryClientProvider>;
+}
+
+afterEach(() => {
+  cleanup();
+  vi.restoreAllMocks();
+  vi.mocked(notifyActionError).mockClear();
+  window.history.replaceState(null, "", "/");
+});
+
+describe("useOpenLinkedPlayer", () => {
+  it("opens the item from the host's list once the list is in, and only once", async () => {
+    window.history.replaceState(null, "", "/?watch=B");
+    const row = vi.spyOn(api, "videoRow");
+    const open = vi.fn();
+    const list = [vid("A"), vid("B")];
+    const { rerender } = renderHook(
+      ({ ready, rows }) => useOpenLinkedPlayer(ready, (id) => rows.find((v) => v.id === id), open),
+      { wrapper, initialProps: { ready: false, rows: list } },
+    );
+    expect(open).not.toHaveBeenCalled();
+    rerender({ ready: true, rows: list });
+    await waitFor(() => expect(open).toHaveBeenCalledWith(list[1], true));
+    // The list refetched (new rows for the same videos): the player it opened is not opened again.
+    rerender({ ready: true, rows: [vid("A"), vid("B")] });
+    expect(open).toHaveBeenCalledTimes(1);
+    expect(row).not.toHaveBeenCalled();
+  });
+
+  it("opens an item the list does not hold alone, its row from the catalog", async () => {
+    window.history.replaceState(null, "", "/?watch=Z");
+    vi.spyOn(api, "videoRow").mockResolvedValue(vid("Z"));
+    const open = vi.fn();
+    renderHook(() => useOpenLinkedPlayer(true, () => undefined, open), { wrapper });
+    await waitFor(() => expect(open).toHaveBeenCalledWith(vid("Z"), false));
+  });
+
+  it("says so when the catalog no longer has it", async () => {
+    window.history.replaceState(null, "", "/?watch=Z");
+    const gone = new Error("not found");
+    vi.spyOn(api, "videoRow").mockRejectedValue(gone);
+    const open = vi.fn();
+    renderHook(() => useOpenLinkedPlayer(true, () => undefined, open), { wrapper });
+    await waitFor(() =>
+      expect(notifyActionError).toHaveBeenCalledWith(gone, msg("player.linkedFailed")),
+    );
+    expect(open).not.toHaveBeenCalled();
+    // Said once: the address no longer names it, so a reload or a copied link does not say it again.
+    expect(new URLSearchParams(window.location.search).has("watch")).toBe(false);
+  });
+
+  it("leaves a player opened while the row was on its way alone, and its address", async () => {
+    window.history.replaceState(null, "", "/?watch=Z");
+    let answer: (v: Video) => void = () => {};
+    vi.spyOn(api, "videoRow").mockReturnValue(new Promise((r) => (answer = r)));
+    const open = vi.fn();
+    renderHook(() => useOpenLinkedPlayer(true, () => undefined, open), { wrapper });
+    // A card clicked meanwhile: its player names itself in the address.
+    window.history.replaceState(null, "", "/?watch=Y");
+    answer(vid("Z"));
+    await new Promise((r) => setTimeout(r, 20));
+    expect(open).not.toHaveBeenCalled();
+    expect(new URLSearchParams(window.location.search).get("watch")).toBe("Y");
+  });
+
+  it("does not clear the address of a player opened since when its catalog read fails", async () => {
+    window.history.replaceState(null, "", "/?watch=Z");
+    let refuse: (e: Error) => void = () => {};
+    vi.spyOn(api, "videoRow").mockReturnValue(new Promise((_, r) => (refuse = r)));
+    renderHook(() => useOpenLinkedPlayer(true, () => undefined, vi.fn()), { wrapper });
+    window.history.replaceState(null, "", "/?watch=Y");
+    refuse(new Error("not found"));
+    await new Promise((r) => setTimeout(r, 20));
+    expect(new URLSearchParams(window.location.search).get("watch")).toBe("Y");
+  });
+
+  it("given up over a moved list, keeps the address of a player opened since", async () => {
+    window.history.replaceState(null, "", "/?watch=Z");
+    const { rerender } = renderHook(
+      ({ scope }) => useOpenLinkedPlayer(false, () => undefined, vi.fn(), scope),
+      { wrapper, initialProps: { scope: 1 } },
+    );
+    window.history.replaceState(null, "", "/?watch=Y");
+    rerender({ scope: 2 });
+    await new Promise((r) => setTimeout(r, 20));
+    expect(new URLSearchParams(window.location.search).get("watch")).toBe("Y");
+  });
+
+  it("stops looking once it opened: the video leaving the list asks the catalog for nothing", async () => {
+    window.history.replaceState(null, "", "/?watch=B");
+    const row = vi.spyOn(api, "videoRow").mockResolvedValue(vid("B"));
+    const find = vi.fn((id: string) => (id === "B" ? vid("B") : undefined));
+    const { rerender } = renderHook(
+      ({ rows }) => useOpenLinkedPlayer(true, rows ? find : () => undefined, vi.fn()),
+      { wrapper, initialProps: { rows: true } },
+    );
+    await waitFor(() => expect(find).toHaveBeenCalled());
+    find.mockClear();
+    rerender({ rows: false });
+    rerender({ rows: true });
+    await new Promise((r) => setTimeout(r, 20));
+    expect(find).not.toHaveBeenCalled();
+    expect(row).not.toHaveBeenCalled();
+  });
+
+  it("opens nothing, and asks for nothing, for an address that names no player", async () => {
+    window.history.replaceState(null, "", "/?q=talks");
+    const row = vi.spyOn(api, "videoRow");
+    const open = vi.fn();
+    renderHook(() => useOpenLinkedPlayer(true, () => undefined, open), { wrapper });
+    await new Promise((r) => setTimeout(r, 20));
+    expect(open).not.toHaveBeenCalled();
+    expect(row).not.toHaveBeenCalled();
+  });
+});
+
+describe("the shell's LinkedPlayer", () => {
+  it("plays the video alone over a page that hosts no player", async () => {
+    window.history.replaceState(null, "", "/?page=channels&watch=Z");
+    vi.spyOn(api, "videoRow").mockResolvedValue(vid("Z"));
+    render(<LinkedPlayer hosted={false} />, { wrapper });
+    expect(await screen.findByText("playing Z alone")).toBeTruthy();
+  });
+
+  it("leaves it to a page that hosts its own, even once that page has fetched the row", async () => {
+    // The page plays it alone, from the catalog row it asked for: the same cache entry this one reads.
+    window.history.replaceState(null, "", "/?page=home&watch=Z");
+    const qc = new QueryClient({ defaultOptions: { queries: { retry: false } } });
+    qc.setQueryData(qk.videoRow("Z"), vid("Z"));
+    render(
+      <QueryClientProvider client={qc}>
+        <LinkedPlayer hosted />
+      </QueryClientProvider>,
+    );
+    await new Promise((r) => setTimeout(r, 20));
+    expect(screen.queryByText(/playing/)).toBeNull();
+  });
+
+  it("leaves it to a page that hosts its own", async () => {
+    window.history.replaceState(null, "", "/?watch=Z");
+    const row = vi.spyOn(api, "videoRow").mockResolvedValue(vid("Z"));
+    render(<LinkedPlayer hosted />, { wrapper });
+    await new Promise((r) => setTimeout(r, 20));
+    expect(row).not.toHaveBeenCalled();
+    expect(screen.queryByText(/playing/)).toBeNull();
+  });
+});

frontend/src/features/player/useOpenLinkedPlayer.ts

@@ -0,0 +1,70 @@
+import { useEffect, useEffectEvent, useRef, useState } from "react";
+import { useQuery } from "@tanstack/react-query";
+import { api, type Video } from "../../lib/api";
+import { qk } from "../../lib/queryKeys";
+import { linkedPlayer, PLAYER_KEYS } from "../../lib/playerUrlState";
+import { clearParams } from "../../lib/urlState";
+import { notifyActionError } from "../../lib/actionErrors";
+import { msg } from "../../lib/notifications";
+
+/** Opens the player an address names (a reload, a bookmark — lib/playerUrlState) on the page that
+ *  hosts it, once: read as the host mounts, opened once its list is in (`ready`). From the list when the
+ *  item is in it (`find`), so the player plays on through the list; else alone, its row fetched from
+ *  the catalog. A row the catalog no longer has is said, not swallowed.
+ *
+ *  `scope` names the list the address put it over (a playlist, a live search): when the host moves to
+ *  another before it opened, the address under it named something else, and the player is given up —
+ *  opened later, it would start over a list nobody linked, unasked. So it is when a player opened
+ *  meanwhile (a card clicked while the row was on its way): the address names that one now. */
+export function useOpenLinkedPlayer(
+  ready: boolean,
+  find: (id: string) => Video | undefined,
+  open: (video: Video, inList: boolean) => void,
+  scope: string | number | null = null,
+): void {
+  const [linked] = useState(() => linkedPlayer()?.watch ?? null);
+  const [linkedScope] = useState(scope);
+  // Opened, said to be gone or given up, once. A ref for the effect (a StrictMode re-run of it must
+  // not open it twice); the state stops the lookup and the row fetch on screen after it.
+  const done = useRef(linked == null);
+  const [settled, setSettled] = useState(linked == null);
+  const moved = scope !== linkedScope;
+  const waiting = ready && !moved && !settled && linked != null;
+  const listed = waiting ? find(linked) : undefined;
+  const row = useQuery({
+    queryKey: qk.videoRow(linked ?? ""),
+    queryFn: () => api.videoRow(linked!),
+    enabled: waiting && !listed,
+    retry: false,
+  });
+  const openIt = useEffectEvent(open);
+  const failed = useEffectEvent((err: unknown) => {
+    notifyActionError(err, msg("player.linkedFailed"));
+    clearParams(...PLAYER_KEYS);
+  });
+  useEffect(() => {
+    if (done.current) return;
+    const settle = () => {
+      done.current = true;
+      // State, not derived: a one-way decision taken as the list or the row arrives. Derived from
+      // `listed`, the lookup and the row fetch would come back whenever the video left the list.
+      setSettled(true);
+    };
+    // A player opened since names its own: this one is not wanted any more.
+    if (linkedPlayer()?.watch !== linked) return settle();
+    if (moved) {
+      // The address goes on naming it under the new list (a reload would open it there).
+      clearParams(...PLAYER_KEYS);
+      return settle();
+    }
+    // Not before the host is ready: the row's cache entry is shared, so another opener's fetch fills
+    // it here too (a disabled query still reads the cache) — the shell's player over a page that
+    // plays its own would open a second one.
+    if (!ready) return;
+    if (listed) openIt(listed, true);
+    else if (row.data) openIt(row.data, false);
+    else if (row.isError) failed(row.error);
+    else return;
+    settle();
+  }, [linked, moved, ready, listed, row.data, row.isError, row.error]);
+}

frontend/src/features/plexCards/PlexCollectionAdd.tsx

@@ -8,6 +8,7 @@ import { PopoverSurface } from "../../components/ui/AnchoredPopover";
 import { useAnchoredPopover } from "../../components/ui/anchoredPopoverHooks";
 import { MembershipMenu } from "../../components/ui/MembershipMenu";
 import { SURFACE } from "../../components/ui/surfaces";
+import { msg } from "../../lib/notifications";
 
 // "Add to collection…" from a movie or show card's menu: a panel beside the card that ticks the title
 // into or out of its library's manual collections, and names a new one — created with this title in
@@ -67,7 +68,7 @@ export default function PlexCollectionAddAt({
       else await api.plexCollectionAddItem(c.id, ratingKey);
       qc.setQueryData<typeof list.data>(forKey, (old) => flipContains(old, c.id));
     } catch (e) {
-      notifyActionError(e, t("plex.collection.editFailed"));
+      notifyActionError(e, msg("plex.collection.editFailed"));
     }
     refresh();
     setBusy(false);
@@ -83,7 +84,7 @@ export default function PlexCollectionAddAt({
       made = true;
     } catch (e) {
       made = madeOnPlex(e);
-      notifyActionError(e, t("plex.collection.editFailed"));
+      notifyActionError(e, msg("plex.collection.editFailed"));
     }
     refresh();
     setBusy(false);

frontend/src/features/plexCards/PlexPlaylistAdd.tsx

@@ -12,6 +12,7 @@ import Modal from "../../components/ui/Modal";
 import { Pressable } from "../../components/ui/Pressable";
 import { Input } from "../../components/ui/Input";
 import { SURFACE } from "../../components/ui/surfaces";
+import { msg } from "../../lib/notifications";
 
 // What we're adding: a single leaf (movie/episode) or a whole group (a season or an entire show, as a
 // set of episode rating_keys). Groups get a tri-state (none / some / all) per playlist.
@@ -80,7 +81,7 @@ export default function PlexPlaylistAdd({
     } catch (e) {
       notifyActionError(
         e,
-        t(allIn ? "plex.playlistAdd.removeFailed" : "plex.playlistAdd.addFailed"),
+        msg(allIn ? "plex.playlistAdd.removeFailed" : "plex.playlistAdd.addFailed"),
       );
     }
     refresh();
@@ -104,7 +105,7 @@ export default function PlexPlaylistAdd({
     } catch (e) {
       // The create may already have landed when the add fails — `refresh()` in `finally` is what
       // makes that half-done state visible instead of leaving a playlist the dialog never lists.
-      notifyActionError(e, t("plex.playlistAdd.createFailed"));
+      notifyActionError(e, msg("plex.playlistAdd.createFailed"));
     }
     refresh();
     setBusy(false);

frontend/src/features/plexCards/plexCards.lang.dom.test.tsx

@@ -74,6 +74,8 @@ describe("a season's name", () => {
     ["Season 1", 1, "plex.seasonTitle(1)"],
     ["Specials", 0, "plex.specials"],
     ["Book One: Water", 1, "Book One: Water"],
+    ["Season 4", null, "Season 4"],
+    ["", null, "plex.playlist.seasonUnknown"],
   ])("Plex's %j (season %s) reads %j", (title, n, shown) => {
     render(<SeasonCard se={season(title, n)} onOpen={vi.fn()} />);
     expect(screen.getByText(shown)).toBeTruthy();

frontend/src/features/plexCards/usePlexCardActions.tsx

@@ -10,6 +10,7 @@ import { pinPlex, useComfortPin } from "../comfort/comfortPin";
 import { useCopyItems } from "../../components/ui/copyItems";
 import PlexPlaylistAdd, { type PlexAddTarget } from "./PlexPlaylistAdd";
 import { type ActionMenuItem } from "../../components/ui/ActionMenu";
+import { raw } from "../../lib/notifications";
 
 // A Plex title's ONE action list (docs/DESIGN.md "Action placement"): the right-click, the
 // long-press, Shift+F10 and the card's "…" open a menu built here, so every poster grid and rail
@@ -151,7 +152,7 @@ export function usePlexCardActions(handlers: PlexActionHandlers, open: boolean)
           ]
         : []),
       ...copy(c.title, null).map((it) => ({ ...it, separatorBefore: !onInfo })),
-      ...(withPin ? pin.item(pinPlex(c), c.title) : []),
+      ...(withPin ? pin.item(pinPlex(c), raw(c.title)) : []),
     ];
   };
 

frontend/src/features/video/AddToPlaylist.tsx

@@ -13,6 +13,7 @@ import { useAnchoredPopover } from "../../components/ui/anchoredPopoverHooks";
 import { IconButton } from "../../components/ui/IconButton";
 import { MembershipMenu } from "../../components/ui/MembershipMenu";
 import { SURFACE } from "../../components/ui/surfaces";
+import { msg } from "../../lib/notifications";
 
 // A small anchored menu for toggling a video's membership in the user's playlists, with inline
 // "new playlist" creation. Its body is the shared MembershipMenu (as the channel tag editor's).
@@ -122,7 +123,7 @@ function MembershipPanel({
         old?.map((p) => (p.id === pl.id ? { ...p, has_video: !p.has_video } : p)),
       );
     } catch (e) {
-      notifyActionError(e, t(pl.has_video ? "playlists.removeFailed" : "playlists.addFailed"));
+      notifyActionError(e, msg(pl.has_video ? "playlists.removeFailed" : "playlists.addFailed"));
     }
     refresh();
     setBusy(false);
@@ -137,7 +138,7 @@ function MembershipPanel({
       await addPlaylistItem(qc, pl, videoId);
       made = true;
     } catch (e) {
-      notifyActionError(e, t("playlists.addFailed"));
+      notifyActionError(e, msg("playlists.addFailed"));
     }
     refresh();
     setBusy(false);

frontend/src/features/video/ChannelNameLink.dom.test.tsx

@@ -48,8 +48,9 @@ describe("ChannelNameLink", () => {
   it("is an anchor whose href opens this channel on the current page", () => {
     const { link } = renderLink();
     expect(link.tagName).toBe("A");
-    // The same URL openChannel pushes: the current page's query plus ?chan=<id>.
-    expect(link.getAttribute("href")).toBe(`/?page=feed&show=unwatched&chan=${CH}`);
+    // The same URL openChannel pushes: the current page plus ?chan=<id> — not the page's own keys,
+    // which named a view the channel does not show (`show=unwatched` here).
+    expect(link.getAttribute("href")).toBe(`/?page=feed&chan=${CH}`);
   });
 
   it("takes the in-app path on a plain left click, and suppresses the browser navigation", () => {
@@ -73,11 +74,16 @@ describe("ChannelNameLink", () => {
     expect(onOpenInApp).not.toHaveBeenCalled();
   });
 
-  it("does not lose the rest of the address bar", () => {
-    window.history.replaceState({}, "", "/?page=channels&q=abc");
+  // The address names only what the screen shows: the channel over the page, not the page's filters
+  // (a link's new tab once opened the channel under the feed's search and sort).
+  it("keeps the page and the shell's keys, and leaves the page's and another channel's behind", () => {
+    window.history.replaceState(
+      {},
+      "",
+      "/?page=channels&q=abc&ctab=hidden&chtab=about&m=signup#x=1",
+    );
     const { link } = renderLink();
-    expect(link.getAttribute("href")).toContain("page=channels");
-    expect(link.getAttribute("href")).toContain("q=abc");
+    expect(link.getAttribute("href")).toBe(`/?page=channels&chan=${CH}&m=signup#x=1`);
   });
 
   it("gives a channel with no title yet an accessible name", () => {

frontend/src/features/video/ChannelNameLink.tsx

@@ -1,15 +1,15 @@
 import { forwardRef, type AnchorHTMLAttributes } from "react";
 import { useTranslation } from "react-i18next";
 import { isPlainLeftClick } from "../../lib/nav";
-import { urlWithParams } from "../../lib/urlState";
+import { channelUrl } from "../../lib/urlState";
 
 // A channel name that is a REAL link. The player showed it as a `<button>`, so the browser's own
 // gestures did nothing on it: middle-click and Ctrl/Cmd-click opened no tab, on a thing that looks
 // exactly like a link (the YouTube icon right next to it IS an anchor and does open one). The video
 // card's channel name had the same `<button>`, so it renders through here too.
 //
-// The href is the same URL `openChannel` pushes — `?chan=<id>` on the current page — so a new tab
-// lands where the in-app navigation would have. A plain left click is still handled in-app, because
+// The href is the same URL `openChannel` pushes (`channelUrl`: the channel over the current page,
+// without the page's own keys) — so a new tab lands where the in-app navigation would have. A plain left click is still handled in-app, because
 // the SPA path does more than navigate (the player has to close first and reclaim its own
 // Back-to-close history entry; see lib/history.closeOverlaysThenNavigate).
 type Props = Omit<AnchorHTMLAttributes<HTMLAnchorElement>, "href" | "onClick" | "title"> & {
@@ -33,7 +33,7 @@ const ChannelNameLink = forwardRef<HTMLAnchorElement, Props>(function ChannelNam
     <a
       {...rest}
       ref={ref}
-      href={urlWithParams({ chan: channelId })}
+      href={channelUrl(channelId)}
       title={tooltip}
       onClick={(e) => {
         if (stopPropagation) e.stopPropagation();

frontend/src/features/video/stateNotice.ts

@@ -1,5 +1,5 @@
 import i18n from "../../i18n";
-import { notify, resolveVideo } from "../../lib/notifications";
+import { msg, notify, raw, resolveVideo } from "../../lib/notifications";
 import type { Video, VideoStatus } from "../../lib/api";
 
 /** What a notice names the video by; any of it may be unknown to the surface that marked it. */
@@ -24,9 +24,9 @@ export function announceVideoState(
   const hidden = status === "hidden";
   notify({
     message: video?.title
-      ? i18n.t(hidden ? "feed.hiddenNamed" : "feed.markedWatchedNamed", { title: video.title })
-      : i18n.t(hidden ? "feed.hidden" : "feed.markedWatched"),
-    action: { label: i18n.t(hidden ? "feed.undo" : "feed.unwatch"), onClick: undo },
+      ? msg(hidden ? "feed.hiddenNamed" : "feed.markedWatchedNamed", { title: raw(video.title) })
+      : msg(hidden ? "feed.hidden" : "feed.markedWatched"),
+    action: { label: msg(hidden ? "feed.undo" : "feed.unwatch"), onClick: undo },
     meta: {
       kind: hidden ? "video-hidden" : "video-watched",
       videoId: id,

frontend/src/features/video/useVideoActions.tsx

@@ -27,6 +27,7 @@ import { useCopyItems } from "../../components/ui/copyItems";
 import { useNavigationActions } from "../navigation/navigationContext";
 import { type ActionMenuItem } from "../../components/ui/ActionMenu";
 import { VideoFollowUp, type VideoFollowUpState } from "./VideoFollowUp";
+import { raw } from "../../lib/notifications";
 
 // A video's ONE action list (docs/DESIGN.md "Action placement"). The right-click, the
 // long-press, Shift+F10 and the card's "…" all open a menu built here, so the feed, a channel page
@@ -198,7 +199,7 @@ export function useVideoActions(handlers: VideoActionHandlers, open: boolean) {
             },
           ]
         : []),
-      ...(withPin ? pin.item(pinVideo(v.id), v.title ?? "") : []),
+      ...(withPin ? pin.item(pinVideo(v.id), raw(v.title ?? "")) : []),
     ];
   };
 

frontend/src/features/wizard/OnboardingWizard.dialog.dom.test.tsx

@@ -23,7 +23,7 @@ vi.mock("../../lib/onboarding", () => ({ beginGrant: vi.fn(), endOnboarding: vi.
 
 import OnboardingWizard from "./OnboardingWizard";
 import { api, type Me } from "../../lib/api";
-import { clearAll, notify } from "../../lib/notifications";
+import { clearAll, notify, raw } from "../../lib/notifications";
 
 const me = { id: 1, email: "a@b", can_read: false, can_write: false } as unknown as Me;
 
@@ -110,7 +110,7 @@ describe("the onboarding wizard as a dialog", () => {
     document.body.appendChild(outside);
     outside.focus();
     const { unmount } = mount();
-    act(() => void notify({ level: "error", message: "offline" }));
+    act(() => void notify({ level: "error", message: raw("offline") }));
     const dismissToast = screen.getByTitle("notifications.dismiss");
     dismissToast.focus();
     expect(document.activeElement).toBe(dismissToast);
@@ -126,7 +126,7 @@ describe("the onboarding wizard as a dialog", () => {
     // unreachable from the keyboard. `ui/Modal` spans the whole dialog for exactly this reason.
     mount();
     const panel = screen.getByRole("dialog");
-    act(() => void notify({ level: "error", message: "offline" }));
+    act(() => void notify({ level: "error", message: raw("offline") }));
     try {
       const dismissToast = screen.getByTitle("notifications.dismiss");
       expect(panel.contains(dismissToast)).toBe(false);

frontend/src/i18n/backendIds.contract.test.ts

@@ -1,7 +1,15 @@
+import { execFileSync } from "node:child_process";
 import { readdirSync, readFileSync } from "node:fs";
+import { fileURLToPath } from "node:url";
 import { describe, expect, it } from "vitest";
 
 import { RUN_STATUSES } from "../lib/activityUrlState";
+import {
+  REFUSAL_BY_REASON,
+  REFUSAL_FAMILIES,
+  REFUSAL_FIXED,
+  REFUSAL_UNSHOWN,
+} from "../lib/api/refusalCodes";
 import { vocabKey } from "../lib/vocab";
 
 // Every id the BACKEND owns and the UI names must have its name in both languages. The UI looks these
@@ -21,6 +29,25 @@ import { vocabKey } from "../lib/vocab";
 const backend = (file: string) =>
   readFileSync(new URL(`../../../backend/app/${file}`, import.meta.url), "utf-8");
 
+// Every refusal the backend can answer, read from its syntax tree by `backend/tests/refusal_sites.py`
+// (stdlib `ast`, on the host's Python, as the ruff lane is): each code with every reason it can be sent
+// with — a reason in a variable followed to its `Literal` type, its helper's every call, its map — and
+// what it could not follow, which fails below. It also hands back every `Literal` alias it read.
+type RefusalScan = {
+  codes: Record<string, { reasons: string[]; unread: string[]; reasonless: string[] }>;
+  unreadCodes: string[];
+  errors: string[];
+  notRefusals: string[];
+  excluded: Record<string, number>;
+  aliases: Record<string, Record<string, string[]>>;
+};
+const scan = JSON.parse(
+  execFileSync("python", ["-I", "backend/tests/refusal_sites.py"], {
+    cwd: fileURLToPath(new URL("../../../", import.meta.url)),
+    encoding: "utf-8",
+  }),
+) as RefusalScan;
+
 const mods = import.meta.glob("./locales/*/*.json", { eager: true }) as Record<
   string,
   { default: Record<string, unknown> }
@@ -48,12 +75,11 @@ const keysOf = (lang: string): Set<string> => {
 const specs = [
   ...backend("sysconfig.py").matchAll(/ConfigSpec\(\s*"(\w+)",\s*"(\w+)",\s*"(\w+)",\s*"(\w+)"/g),
 ].map((m) => ({ key: m[1]!, type: m[2]!, group: m[3]!, attr: m[4]! }));
-// A choice key's options, as config.py spells them: `<attr>: <Alias> = …` → `<Alias> = Literal[…]`.
+// A choice key's options, as config.py spells them: `<attr>: <Alias> = …`, the alias's values from the scan.
 const configPy = backend("config.py");
 const choicesOf = (attr: string): string[] => {
   const alias = configPy.match(new RegExp(`^\\s+${attr}: (\\w+) =`, "m"))?.[1];
-  const body = alias && configPy.match(new RegExp(`^${alias} = Literal\\[([^\\]]*)\\]`, "m"))?.[1];
-  return [...(body ?? "").matchAll(/"(\w+)"/g)].map((m) => m[1]!);
+  return (alias && scan.aliases["config.py"]?.[alias]) || [];
 };
 const choiceIds = specs
   .filter((s) => s.type === "choice")
@@ -84,20 +110,10 @@ const runEnum = (name: string) =>
 const runStatuses = runEnum("RunStatus");
 const runTriggers = runEnum("RunTrigger");
 const quotaActions = enumValues("quota.py");
-// The admin actions' refusal reasons → `errors.admin.<reason>`. The codes are read from
-// `localizeDetail`'s own ADMIN_REFUSALS, so a code added there is scanned here too; a detail dict
-// ruff wraps over several lines still matches.
-const adminCodes = [
-  ...(
-    readFileSync(new URL("../lib/api/core.ts", import.meta.url), "utf-8").match(
-      /ADMIN_REFUSALS = new Set\(\[([^\]]*)\]/,
-    )?.[1] ?? ""
-  ).matchAll(/"(\w+)"/g),
-].map((m) => m[1]!);
-const adminRefusals = [
-  ...backend("routes/admin.py").matchAll(/\{\s*"code":\s*"(\w+)",\s*"reason":\s*"(\w+)"/g),
-].filter((m) => adminCodes.includes(m[1]!));
-const adminReasons = [...new Set(adminRefusals.map((m) => m[2]!))];
+// The admin actions' refusals → `errors.admin.<reason>`: the codes recorded under that prefix.
+const adminCodes = Object.entries(REFUSAL_FAMILIES)
+  .filter(([, f]) => f.prefix === "errors.admin")
+  .map(([code]) => code);
 // The download failure catalog's host-specific entries → `downloads.errors.fail.catalog.<detail>`.
 // A code holds a dot (`facebook.login_wall`), so the reverse check strips the prefix and the part
 // rather than splitting on dots.
@@ -118,102 +134,46 @@ const failCategories = [
   ]),
 ];
 
-// What a structured 404 says is gone → `errors.notFound.<what>`: every `not_found("x")` and every
-// `owned_or_404(..., what="x")` / `get_or_404(..., what="x")` under routes/, read from the sources.
-const routeFiles = (dir = "routes"): string[] =>
-  readdirSync(new URL(`../../../backend/app/${dir}/`, import.meta.url), {
+// Every backend source, by its path under app/.
+const appPaths = (dir = ""): string[] =>
+  readdirSync(new URL(`../../../backend/app/${dir}`, import.meta.url), {
     withFileTypes: true,
   }).flatMap((e) =>
     e.isDirectory()
-      ? routeFiles(`${dir}/${e.name}`)
+      ? e.name === "__pycache__"
+        ? []
+        : appPaths(`${dir}${e.name}/`)
       : e.name.endsWith(".py")
-        ? [`${dir}/${e.name}`]
+        ? [`${dir}${e.name}`]
         : [],
   );
-const routeSources = (): string[] => routeFiles().map(backend);
 // The words a job's result gives for not doing its work → `scheduler.skip.<vocabKey(word)>` (the Scheduler
 // page, the run notice and the audit row name them; lib/jobResult). Read as the `"skipped": "…"` /
 // `"reason": "…"` literals of the non-HTTP backend: under routes/ (and main.py) a `reason` is a refusal
 // code, which `errors.*` names. A word from an exception's text is not a literal and is not covered.
-const appFiles = (dir: string): string[] =>
-  readdirSync(new URL(`../../../backend/app/${dir}`, import.meta.url), {
-    withFileTypes: true,
-  }).flatMap((e) =>
-    e.isDirectory()
-      ? e.name === "routes" || e.name === "__pycache__"
-        ? []
-        : appFiles(`${dir}${e.name}/`)
-      : e.name.endsWith(".py") && `${dir}${e.name}` !== "main.py"
-        ? [`${dir}${e.name}`]
-        : [],
-  );
 const skipWords = [
   ...new Set(
-    appFiles("").flatMap((f) =>
-      [...backend(f).matchAll(/"(?:skipped|reason)": "([^"]+)"/g)].map((m) => m[1]!),
-    ),
-  ),
-];
-// A target the scan cannot read — `what=SOME_CONSTANT` — is a 404 no locale is checked for (one hid
-// `debug_session`). Only the helpers' own pass-through in `_common.py` may name it by variable.
-const opaqueWhats = routeFiles()
-  .filter((f) => !f.endsWith("/_common.py"))
-  .flatMap((f) =>
-    [...backend(f).matchAll(/not_found\((?!"|\))[^)]*\)|what=(?!")\S+/g)].map(
-      (m) => `${f}: ${m[0]}`,
-    ),
-  );
-const goneWhats = [
-  ...new Set(
-    routeSources().flatMap((src) =>
-      [...src.matchAll(/not_found\("(\w+)"\)|what="(\w+)"/g)].map((m) => (m[1] ?? m[2])!),
-    ),
-  ),
-];
-// Every generic refusal → `errors.refused.<reason>`: each `refused(<status>, "<reason>")` anywhere in
-// the backend (not `_refused`, a router's own family), plus the values of the settings map, which
-// `setting_refused` picks from at runtime, and every `FolderError` reason.
-const appSources = (dir = ""): string[] =>
-  readdirSync(new URL(`../../../backend/app/${dir}`, import.meta.url), {
-    withFileTypes: true,
-  }).flatMap((e) =>
-    e.isDirectory()
-      ? appSources(`${dir}${e.name}/`)
-      : e.name.endsWith(".py")
-        ? [backend(`${dir}${e.name}`)]
-        : [],
-  );
-const refusedReasons = [
-  ...new Set([
-    ...appSources().flatMap((src) =>
-      [...src.matchAll(/(?<![\w.])refused\(\s*\d+,\s*"(\w+)"/g)].map((m) => m[1]!),
-    ),
-    // A folder change the rules refuse travels as `FolderError("<reason>")` and is answered with
-    // `refused(409, e.reason)`, which the pattern above cannot read.
-    ...appSources().flatMap((src) =>
-      [...src.matchAll(/FolderError\("(\w+)"\)/g)].map((m) => m[1]!),
-    ),
-    ...[
-      ...(backend("refusal.py").split("_SETTING_REASONS = {")[1]?.split("}")[0] ?? "").matchAll(
-        /:\s*"(\w+)"/g,
+    appPaths()
+      .filter((f) => !f.startsWith("routes/") && f !== "main.py")
+      .flatMap((f) =>
+        [...backend(f).matchAll(/"(?:skipped|reason)": "([^"]+)"/g)].map((m) => m[1]!),
       ),
-    ].map((m) => m[1]!),
-  ]),
-];
-// A refused YouTube action → `errors.youtube.<reason>`, the reasons read from their Literal.
-const youtubeReasons = [
-  ...(
-    backend("youtube/client.py").match(/^YouTubeRefusal = Literal\[([^\]]*)\]/m)?.[1] ?? ""
-  ).matchAll(/"(\w+)"/g),
-].map((m) => m[1]!);
-// A clip the server will not cut → `clip.errors.<reason>`: every `ClipError("<reason>"…)` in the backend
-// (a reason may carry its numbers after it: `ClipError("too_long", limit_s=…)`).
-const clipReasons = [
-  ...new Set(
-    appSources().flatMap((src) => [...src.matchAll(/ClipError\("(\w+)"[,)]/g)].map((m) => m[1]!)),
   ),
 ];
 
+const backendCodes = Object.keys(scan.codes);
+const recordedCodes = [
+  ...Object.keys(REFUSAL_FAMILIES),
+  ...Object.keys(REFUSAL_BY_REASON),
+  ...Object.keys(REFUSAL_FIXED),
+  ...Object.keys(REFUSAL_UNSHOWN),
+];
+// The codes whose reason picks the sentence, and what each can carry as its reason.
+const reasoned = [...Object.keys(REFUSAL_FAMILIES), ...Object.keys(REFUSAL_BY_REASON)];
+const reasonsOf: Record<string, string[]> = Object.fromEntries(
+  reasoned.map((code) => [code, scan.codes[code]?.reasons ?? []]),
+);
+
 // The closed English vocabularies the backend WRITES into data, named through `vocab.<group>`
 // (lib/vocab) by their letters-and-digits key. A word the backend adds shows in English until named —
 // so each list is read from its source here: the TMDB crew jobs kept, every auto-tag the tagger can
@@ -275,10 +235,11 @@ describe("backend ids have their names in both languages", () => {
     expect(runTriggers).toEqual(expect.arrayContaining(["scheduled", "ad_hoc"]));
     expect(adminCodes).toEqual(expect.arrayContaining(["activate", "resend"]));
     expect(failDetails).toEqual(expect.arrayContaining(["facebook.login_wall"]));
-    expect(goneWhats).toEqual(expect.arrayContaining(["playlist", "download", "job"]));
-    expect(opaqueWhats).toEqual([]);
-    expect(youtubeReasons).toEqual(["quota", "reconnect", "unavailable", "gone"]);
-    expect(clipReasons).toEqual(expect.arrayContaining(["too_long", "past_end", "bad_crop"]));
+    expect(reasonsOf.not_found).toEqual(
+      expect.arrayContaining(["playlist", "download", "job", "user", "debug_session"]),
+    );
+    expect(reasonsOf.youtube).toEqual(["gone", "quota", "reconnect", "unavailable"]);
+    expect(reasonsOf.clip).toEqual(expect.arrayContaining(["too_long", "past_end", "bad_crop"]));
     expect(crewJobs).toEqual(
       expect.arrayContaining(["Director", "Creator", "Director of Photography"]),
     );
@@ -294,11 +255,46 @@ describe("backend ids have their names in both languages", () => {
         "no service user",
       ]),
     );
-    expect(refusedReasons).toEqual(
-      expect.arrayContaining(["weak_password", "setting_too_low", "plex_write_failed"]),
+    expect(reasonsOf.refused).toEqual(
+      expect.arrayContaining([
+        "weak_password",
+        "setting_too_low",
+        "plex_write_failed",
+        "file_folder_gone",
+      ]),
     );
-    // Every code the frontend localizes is raised somewhere the scan can see.
-    expect(adminCodes.filter((c) => !adminRefusals.some((m) => m[1] === c))).toEqual([]);
+  });
+
+  it("every refusal code the backend answers is said by exactly one record, and no record names another", () => {
+    expect(backendCodes).toEqual(expect.arrayContaining(["refused", "playlist", "too_large"]));
+    expect(backendCodes.filter((c) => recordedCodes.filter((r) => r === c).length !== 1)).toEqual(
+      [],
+    );
+    expect(recordedCodes.filter((c) => !backendCodes.includes(c))).toEqual([]);
+  });
+
+  it("every refusal code and reason is one the scan can follow", () => {
+    // The modules set aside as not refusals still use the key.
+    expect(Object.keys(scan.excluded).sort()).toEqual(scan.notRefusals);
+    expect(scan.unreadCodes).toEqual([]);
+    expect(scan.errors).toEqual([]);
+    // A reason it could not follow is a sentence nobody is asked for, unless no screen says that code.
+    expect(
+      Object.entries(scan.codes)
+        .filter(([code]) => !(code in REFUSAL_UNSHOWN))
+        .flatMap(([, c]) => c.unread),
+    ).toEqual([]);
+    // A code whose reason picks the sentence, sent without one, says only its fallback.
+    expect(reasoned.flatMap((code) => scan.codes[code]?.reasonless ?? [])).toEqual([]);
+  });
+
+  it("every code whose reason picks the sentence is read with a reason (a scan that matches nothing is green over nothing)", () => {
+    expect(Object.entries(reasonsOf).filter(([, rs]) => rs.length === 0)).toEqual([]);
+  });
+
+  it("a code whose reasons share sentences names every reason it is sent with, and no other", () => {
+    for (const [code, { reasons }] of Object.entries(REFUSAL_BY_REASON))
+      expect(Object.keys(reasons).sort(), code).toEqual([...reasonsOf[code]!].sort());
   });
 
   it("the run list's status chips are the server's run statuses", () => {
@@ -418,33 +414,6 @@ describe("backend ids have their names in both languages", () => {
       expect([...named].filter((d) => !failDetails.includes(d))).toEqual([]);
     });
 
-    it(`${lang}: every "that is gone" a 404 names, and every YouTube refusal`, () => {
-      expect(missing(goneWhats.map((w) => `errors.notFound.${w}`))).toEqual([]);
-      expect(
-        [...idsUnder(keys, "errors.notFound")].filter(
-          (w) => w !== "generic" && !goneWhats.includes(w),
-        ),
-      ).toEqual([]);
-      expect(missing(youtubeReasons.map((r) => `errors.youtube.${r}`))).toEqual([]);
-      expect(
-        [...idsUnder(keys, "errors.youtube")].filter((r) => !youtubeReasons.includes(r)),
-      ).toEqual([]);
-    });
-
-    it(`${lang}: every generic refusal the backend can answer, and none it cannot`, () => {
-      expect(missing(refusedReasons.map((r) => `errors.refused.${r}`))).toEqual([]);
-      expect(
-        [...idsUnder(keys, "errors.refused")].filter((r) => !refusedReasons.includes(r)),
-      ).toEqual([]);
-    });
-
-    it(`${lang}: every reason a clip is refused, and none it cannot be`, () => {
-      expect(missing(clipReasons.map((r) => `clip.errors.${r}`))).toEqual([]);
-      expect([...idsUnder(keys, "clip.errors")].filter((r) => !clipReasons.includes(r))).toEqual(
-        [],
-      );
-    });
-
     it(`${lang}: every crew job, auto-tag and built-in profile the backend writes, and no other`, () => {
       for (const [group, words] of Object.entries(VOCAB)) {
         const wanted = words.map((w) => `vocab.${group}.${vocabKey(w)}`);
@@ -456,11 +425,49 @@ describe("backend ids have their names in both languages", () => {
       }
     });
 
-    it(`${lang}: every admin refusal reason`, () => {
-      expect(missing(adminReasons.map((r) => `errors.admin.${r}`))).toEqual([]);
-      expect([...idsUnder(keys, "errors.admin")].filter((r) => !adminReasons.includes(r))).toEqual(
-        [],
-      );
+    it(`${lang}: every refusal the backend can answer has its sentence`, () => {
+      const wanted = [
+        ...Object.entries(REFUSAL_FAMILIES).flatMap(([code, f]) => [
+          ...reasonsOf[code]!.map((r) => `${f.prefix}.${r}${"suffix" in f ? f.suffix : ""}`),
+          f.fallback,
+        ]),
+        ...Object.values(REFUSAL_BY_REASON).flatMap((f) => [
+          ...Object.values(f.reasons),
+          f.fallback,
+        ]),
+        ...Object.values(REFUSAL_FIXED),
+        "errors.generic",
+      ];
+      expect(missing([...new Set(wanted)])).toEqual([]);
+    });
+
+    it(`${lang}: no sentence for a refusal reason the backend cannot send`, () => {
+      // By prefix: the admin actions share `errors.admin`. A suffixed family shares its prefix with more
+      // than its refusals — the sign-in screens' `gate`, `addressLabel` — so only an id with the
+      // refusal's own key counts as a reason there.
+      const byPrefix = new Map<
+        string,
+        { suffix: string; reasons: Set<string>; spare: Set<string> }
+      >();
+      for (const [code, f] of Object.entries(REFUSAL_FAMILIES)) {
+        const p = byPrefix.get(f.prefix) ?? {
+          suffix: "suffix" in f ? f.suffix : "",
+          reasons: new Set<string>(),
+          spare: new Set<string>(),
+        };
+        for (const r of reasonsOf[code]!) p.reasons.add(r);
+        if (f.fallback.startsWith(`${f.prefix}.`))
+          p.spare.add(f.fallback.slice(f.prefix.length + 1));
+        byPrefix.set(f.prefix, p);
+      }
+      for (const [prefix, { suffix, reasons, spare }] of byPrefix)
+        expect(
+          [...idsUnder(keys, prefix)].filter(
+            (r) =>
+              (!suffix || keys.has(`${prefix}.${r}${suffix}`)) && !spare.has(r) && !reasons.has(r),
+          ),
+          prefix,
+        ).toEqual([]);
     });
   }
 });

frontend/src/i18n/locales/en/downloads.json

@@ -219,6 +219,7 @@
     "edit": {
       "empty_edit": "Choose a trim range or crop area first",
       "source_not_ready": "The source download isn't ready to edit",
+      "not_media": "Only video and audio can be edited",
       "generic": "Couldn't create that edit"
     },
     "upload": {

frontend/src/i18n/locales/en/feed.json

@@ -75,6 +75,9 @@
     "clearNow": "Clear now",
     "cleared_one": "Cleared {{count}} result",
     "cleared_other": "Cleared {{count}} results",
-    "showHint": "How many results to fetch at a time — “Load more” pulls another batch of this size."
+    "showHint": "How many results to fetch at a time — “Load more” pulls another batch of this size.",
+    "notRunTitle": "Not searched yet",
+    "notRunBody": "A YouTube API search spends 100 units of the shared daily quota, so a reload, a link, Back or Forward doesn't start one by itself.",
+    "runAgain": "Search YouTube"
   }
 }