fix(e12): close the eighteen findings the E12 review round left standing

The deep review of the branch raised 47 findings, 18 of which survived adversarial
verification. Grouped by what they actually were:

**The size ceiling inverted at its boundary.** `remaining_bytes` clamped to 0 for a user
already at their storage cap, and `build_ydl_opts` reads 0 as "no limit" — so the one
user over quota was the only one downloading with no ceiling at all. `check_enqueue`
could not catch it: it ran while the job was queued and the user was still under the cap.
The arithmetic moves into `quota.remaining_bytes` (where every other max_bytes decision
lives, and where it can be tested), and the worker now fails the job outright rather than
proceeding unbounded — as a non-retryable `quota_exceeded`, since retrying cannot help
until space is freed.

**Silent failures in the new account panel.** All three actions went through `quiet: true`
endpoints, which suppress the global error dialog on the promise that the caller reports
inline — with no `onError`, that promise was broken and a refusal rendered as nothing. On
the broken-SMTP instance this panel exists for, an admin would read silence as "the mail
went out". The co-invalidation set and the email-off predicate move to `lib/adminUsers`,
shared with the pending-access queue, so the two copies of these mutations cannot drift
apart again — which is how half of this was lost in the first place.

**A rollback recipe that destroyed data without working.** `alembic downgrade -1` steps
back one migration, but a release routinely ships several (0.80.0 shipped four): it drops
the newest one's columns and leaves the schema at a revision the older image also cannot
resolve, i.e. the crash loop it was meant to escape, minus the data. The dump restore is
now the recommended path, and the alembic route asks the target version for its own head
revision instead of counting backwards.

Also: redirects named in the urlguard docstring beside the DNS-rebinding residual they
share a fix with (SEC-17); a malformed port refused as `bad_port` instead of escaping as
a 500; the pull cooldown extended to the sibling route spending the same QuotaAction;
restore stops the app before dropping its tables; the PowerShell cleanup can no longer
decide the script's verdict on 5.1, nor report the wrong exit code; the documented
one-liners hardened to match the scripts; the registry's retention window stated where
pinning is advertised; the two banners made mutually exclusive so neither can shadow the
other; `hover:bg-hover` (a utility this project never generated) replaced by the
`selectable` recipe; the clipboard helper reused; and the sync cooldown's copy swept to
the two callers that discarded it.

Verified: gate green (vitest 678, pytest 949), and the panel, the row hover and the reset
banner UAT'd on localdev.

backend/app/downloads/errors.py

@@ -8,9 +8,19 @@ explanation (and decides whether a retry makes sense). The raw text stays availa
 `_RETRIABLE_MARKERS` — kept here as the single source of truth for "what kind of failure is this".
 """
 
+# Failure texts the WORKER itself raises, as opposed to ones yt-dlp/ffmpeg produce. They live here,
+# beside the rules that classify them, because a message and its category drifting apart is exactly
+# how a category silently becomes unreachable — the rule below matches a fragment of each, and
+# test_download_errors pins that they still classify as intended.
+QUOTA_FULL_MESSAGE = "Your download storage is full — free up space, then try again."
+NETWORK_REDACTED_MESSAGE = "The server could not reach that address."
+
 # (marker, category) — first match wins, so order most-specific → most-general. Matching is
 # case-insensitive on a substring, against the raw yt-dlp/ffmpeg message.
 _RULES: tuple[tuple[str, str], ...] = (
+    # Our own refusal: the worker found the user already at their storage cap (SEC-13). Placed
+    # first — it is our wording, so it can never be a false match on an upstream message.
+    ("download storage is full", "quota_exceeded"),
     # Login / age / members / bot-check — the user must be signed in (we deliberately are not).
     ("sign in to confirm your age", "login_required"),
     ("confirm your age", "login_required"),
@@ -91,3 +101,20 @@ def classify(msg: str | None) -> str:
         if marker in low:
             return category
     return "unknown"
+
+
+def user_error_text(source_kind: str, msg: str, code: str) -> str:
+    """The failure text to STORE on the job, given the raw message and its category.
+
+    SEC-12: for a user-supplied URL, a transport-level failure text distinguishes "connection
+    refused" from "HTTP Error 401" from "timed out" per host:port — which is a port scanner with
+    extra steps, since the raw text is shown to the user behind the details disclosure. `urlguard`
+    stops the fetch aiming at our own network; this stops the remaining readout.
+
+    Only the network class, and only for ``url`` jobs: a YouTube job has no user-chosen host, and
+    every other class (login_required, geo_blocked, drm, …) is real, useful diagnosis. A separate
+    function rather than an inline branch in the worker so it can be pinned by a test — the raw
+    text leaking back is a security regression that would otherwise pass a green suite."""
+    if source_kind == "url" and code == "network":
+        return NETWORK_REDACTED_MESSAGE
+    return msg

backend/app/downloads/pipeline.py

@@ -440,13 +440,19 @@ def _download(
                 cookiefile = credentials.resolve_cookiefile(
                     cdb, user_id, url, asset_sig, spec, staging
                 )
-            # SEC-13: what this user has left. `check_enqueue` only compares the CURRENT footprint
-            # against the cap — a download's size is unknown until it finishes, so a single job could
-            # previously blow through the cap by any amount. Handing the remainder to yt-dlp as
-            # `max_filesize` makes the format selector refuse an oversized file up front instead.
-            lim = quota.resolve(cdb, user_id)
-            if not lim.unlimited:
-                remaining_bytes = max(0, lim.max_bytes - quota.footprint(cdb, user_id))
+            # SEC-13: what this user has left. `check_enqueue` only compared the footprint as it
+            # stood when the job was QUEUED — a download's size is unknown until it finishes, so a
+            # single job could previously blow through the cap by any amount. Handing the remainder
+            # to yt-dlp as `max_filesize` makes the format selector refuse an oversized file up
+            # front instead.
+            remaining_bytes = quota.remaining_bytes(cdb, user_id)
+        # …and zero is a REFUSAL, not "no limit". Earlier jobs of this user may have filled the cap
+        # while this one sat in the queue, and 0 is not an expressible yt-dlp `max_filesize`, so
+        # passing it down would leave the ceiling unset — the one user already at their cap would be
+        # the only one downloading unbounded. Fail the job here instead. Not retryable until they
+        # free space, which is what the `quota_exceeded` category tells them.
+        if remaining_bytes == 0:
+            raise RuntimeError(dlerrors.QUOTA_FULL_MESSAGE)
         info = _media_info(
             _extract_with_fallback(
                 job_id,
@@ -551,14 +557,8 @@ def _download(
     except Exception as exc:  # noqa: BLE001 — surface any failure to the user, keep worker alive
         msg = str(exc)[:500]
         code = dlerrors.classify(msg)
-        # SEC-12: for a user-supplied URL, a transport-level failure text distinguishes "connection
-        # refused" from "HTTP Error 401" from "timed out" per host:port — which is a port scanner
-        # with extra steps, since the raw text is shown to the user behind the details disclosure.
-        # The urlguard above stops it aiming at our own network; this stops the remaining readout.
-        # Only the network class, and only for `url` jobs: a YouTube job has no user-chosen host, and
-        # every other class (login_required, geo_blocked, drm, …) is real, useful diagnosis.
-        if source_kind == "url" and code == "network":
-            msg = "The server could not reach that address."
+        # SEC-12: redact a transport-level readout for user-supplied URLs (see user_error_text).
+        msg = dlerrors.user_error_text(source_kind, msg, code)
         with SessionLocal() as db:
             asset = db.get(MediaAsset, asset_id)
             if asset:

backend/app/downloads/quota.py

@@ -6,7 +6,9 @@ Limits come from a per-user DownloadQuota row if the admin set one, else the sys
 `unlimited` (e.g. the admin's own account) bypasses the byte cap.
 
 Enforcement split: max_jobs + max_bytes are checked at enqueue (they bound holdings); per-user
-max_concurrent is enforced by the worker at claim time (it bounds simultaneous downloads).
+max_concurrent is enforced by the worker at claim time (it bounds simultaneous downloads). max_bytes
+is checked a SECOND time in the worker, via `remaining_bytes` — enqueue can only compare the
+footprint as it stood when the job was created, and earlier jobs may have filled the cap since.
 """
 
 from dataclasses import dataclass
@@ -122,6 +124,21 @@ def check_enqueue(db: Session, user_id: int) -> None:
         raise QuotaExceeded("max_bytes", lim.max_bytes, used)
 
 
+def remaining_bytes(db: Session, user_id: int) -> int | None:
+    """Storage this user may still spend on ONE download: ``None`` for an unlimited user, else the
+    cap minus the current footprint, floored at 0.
+
+    Zero is a real answer, not "no limit" — it means the cap is already met and the caller must
+    REFUSE rather than proceed unbounded. `check_enqueue` cannot make that refusal on the caller's
+    behalf: it ran when the job was queued, while the user was still under the cap, and the jobs
+    that filled it have landed since. Keeping the arithmetic here (rather than inline in the worker)
+    is what keeps every max_bytes decision in this module."""
+    lim = resolve(db, user_id)
+    if lim.unlimited:
+        return None
+    return max(0, lim.max_bytes - footprint(db, user_id))
+
+
 def check_upload(db: Session, user_id: int, add_bytes: int) -> None:
     """Like check_enqueue, but for an upload whose size is KNOWN at ingest: also reject when adding
     this file would push the footprint over max_bytes. A download can't pre-check its size (unknown

backend/app/downloads/urlguard.py

@@ -10,11 +10,19 @@ What this closes: a URL whose host resolves to a loopback / private / link-local
 is refused, at enqueue AND again in the worker before extraction. Both, because DNS can answer
 differently between the two moments, and the worker is where the socket is actually opened.
 
-What it does NOT close, stated plainly rather than implied: a host that passes the worker's check
-and then answers yt-dlp's own resolution with an internal address (DNS rebinding). Closing that
-needs the connection itself to be gated — a custom socket factory inside yt-dlp — which is a much
-larger change than this one. The two checks here stop the straightforward case (typing
-``http://127.0.0.1:6379`` or an internal hostname into the box), which is the reachable one.
+What it does NOT close, stated plainly rather than implied, because both need the same fix — gating
+the connection itself with a custom socket factory inside yt-dlp, a much larger change than this:
+
+* DNS rebinding: a host that passes the worker's check and then answers yt-dlp's own resolution
+  with an internal address.
+* HTTP redirects: a public host that answers 3xx with an internal ``Location``. yt-dlp follows it,
+  and only the URL the user TYPED was ever judged here. An attacker-controlled host or any public
+  open redirect reaches it, so this is the cheaper of the two — but it still buys only what a
+  media-shaped internal response yields, since a non-media body fails the mp4 remux and stores
+  nothing. Tracked as SEC-17.
+
+The two checks here stop the straightforward case (typing ``http://127.0.0.1:6379`` or an internal
+hostname into the box), which is the reachable one.
 
 Not used for YouTube jobs: those resolve to a fixed public host from an 11-char id, so there is no
 user-controlled destination to guard.
@@ -28,6 +36,7 @@ from urllib.parse import urlparse
 # vocabulary (frontend `localizeDetail`) — keep them stable.
 REASON_SCHEME = "scheme"  # not http(s)
 REASON_NO_HOST = "no_host"  # URL carries no hostname
+REASON_BAD_PORT = "bad_port"  # ":99999" / ":abc" — urlparse only raises on ACCESS, 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
 
@@ -79,7 +88,15 @@ def check_url(raw: str) -> None:
     host = u.hostname
     if not host:
         raise BlockedUrl(REASON_NO_HOST)
-    for addr in _resolve(host, u.port):
+    # `.port` is a lazily-parsed property: it raises ValueError for ":99999" or ":abc" on ACCESS,
+    # not at urlparse() time, and `.hostname` above happily returns first. Unguarded, one typo
+    # escapes the caller's `except BlockedUrl` as a 500 instead of the structured 422 this whole
+    # module exists to return.
+    try:
+        port = u.port
+    except ValueError as exc:
+        raise BlockedUrl(REASON_BAD_PORT) from exc
+    for addr in _resolve(host, port):
         try:
             ip = ipaddress.ip_address(addr)
         except ValueError:  # getaddrinfo returned something unparseable; treat as unusable

backend/app/routes/playlists.py

@@ -29,9 +29,22 @@ router = APIRouter(prefix="/api/playlists", tags=["playlists"])
 # caller owns and then every item in each, against the instance-wide YouTube budget. Its own
 # limiter rather than a shared one — spending the manual subscription-import allowance must not
 # also close the playlist button, and vice versa.
+#
+# It guards EVERY route that spends under QuotaAction.PLAYLISTS_PULL, not just the bulk one: a
+# scripted loop over the single-playlist re-pull drains the same shared budget, and limiting one of
+# two routes with the same quota action is the asymmetric fix this codebase keeps re-learning.
+# Deliberately NOT on the push side (`push-plan` / `push`): those run on every push attempt,
+# including the no-op "already up to date" path, so a 3-per-10-minute allowance would refuse
+# legitimate work. Their exposure is tracked as SEC-18 instead.
 _playlist_pull_limiter = RateLimiter(max_events=3, window_seconds=600)
 
 
+def _check_pull_cooldown(user: User) -> None:
+    """Shared gate so the two PLAYLISTS_PULL routes cannot drift apart again."""
+    if not _playlist_pull_limiter.allow(str(user.id)):
+        raise HTTPException(status_code=429, detail={"code": "sync_cooldown"})
+
+
 def _own_playlist(db: Session, user: User, playlist_id: int) -> Playlist:
     pl = db.get(Playlist, playlist_id)
     if pl is None or pl.user_id != user.id:
@@ -291,8 +304,7 @@ def sync_youtube(
             status_code=403,
             detail="Connect YouTube (read access) to sync your playlists.",
         )
-    if not _playlist_pull_limiter.allow(str(user.id)):
-        raise HTTPException(status_code=429, detail={"code": "sync_cooldown"})
+    _check_pull_cooldown(user)
     with quota.attribute(user.id, quota.QuotaAction.PLAYLISTS_PULL):
         return sync_user_playlists(db, user)
 
@@ -313,6 +325,7 @@ def revert_youtube(
         raise HTTPException(
             status_code=403, detail="Connect YouTube (read access) to sync your playlists."
         )
+    _check_pull_cooldown(user)
     try:
         with quota.attribute(user.id, quota.QuotaAction.PLAYLISTS_PULL):
             return repull_playlist(db, user, pl)

backend/tests/test_abuse_limits.py

@@ -85,3 +85,28 @@ def test_the_cooldown_is_per_user_not_global(db, as_user, make_user, monkeypatch
         ca.post("/api/sync/subscriptions")
     assert ca.post("/api/sync/subscriptions").status_code == 429
     assert as_user(b).post("/api/sync/subscriptions").status_code == 200
+
+
+def test_the_single_playlist_repull_shares_the_pull_cooldown(db, as_user, make_user, monkeypatch):
+    # SEC-14, the sweep half: `revert-youtube` spends under the SAME QuotaAction.PLAYLISTS_PULL key
+    # as the bulk `sync-youtube`, so limiting only one of them left the identical drain open one
+    # route over. Both must draw on the one allowance.
+    from app.models import Playlist
+    from app.routes import playlists as plroutes
+
+    user = make_user()
+    pl = Playlist(user_id=user.id, name="Linked", kind="youtube", yt_playlist_id="PL123")
+    db.add(pl)
+    db.commit()
+    monkeypatch.setattr(plroutes, "has_read_scope", lambda u: True)
+    monkeypatch.setattr(plroutes, "repull_playlist", lambda d, u, p: {"ok": True})
+    monkeypatch.setattr(plroutes, "sync_user_playlists", lambda d, u: {"ok": True})
+
+    c = as_user(user)
+    codes = [c.post(f"/api/playlists/{pl.id}/revert-youtube").status_code for _ in range(4)]
+    assert codes[:3] == [200, 200, 200]
+    assert codes[3] == 429
+    # One allowance, not one each: the bulk route is now on cooldown too.
+    r = c.post("/api/playlists/sync-youtube")
+    assert r.status_code == 429
+    assert r.json()["detail"] == {"code": "sync_cooldown"}

backend/tests/test_download_errors.py

@@ -1,5 +1,6 @@
 """Category classification of raw yt-dlp / ffmpeg download-failure strings (S2)."""
 
+from app.downloads import errors as dlerrors
 from app.downloads.errors import classify
 
 
@@ -54,3 +55,22 @@ def test_login_beats_generic_unavailable_when_both_present():
         "This video is unavailable"
     )
     assert classify(msg) == "login_required"
+
+
+def test_our_own_worker_refusals_classify_as_themselves():
+    # The worker raises these itself (not yt-dlp), and the rule that catches each one matches only a
+    # fragment of the text. Pinning message and rule together is what stops an edit to the wording
+    # from silently orphaning the category — the UI would then fall back to "Download failed".
+    assert classify(dlerrors.QUOTA_FULL_MESSAGE) == "quota_exceeded"
+
+
+def test_a_url_jobs_network_failure_is_redacted_but_youtube_keeps_its_text():
+    # SEC-12: the raw transport text for a user-chosen host:port is a port-scanner readout, so it is
+    # replaced for `url` jobs. Everything else must survive verbatim, or a real diagnosis is lost.
+    raw = "ERROR: Unable to download webpage: <urlopen error [Errno 111] Connection refused>"
+    assert dlerrors.user_error_text("url", raw, "network") == dlerrors.NETWORK_REDACTED_MESSAGE
+    # Same failure, but the destination was never user-chosen — nothing to leak, keep the detail.
+    assert dlerrors.user_error_text("youtube", raw, "network") == raw
+    # A user-chosen host, but a category that says something real about the CONTENT, not the network.
+    login = "ERROR: [facebook] 123: You must be logged in to see this post"
+    assert dlerrors.user_error_text("url", login, "login_required") == login

backend/tests/test_download_limits.py

@@ -10,6 +10,7 @@ Uses the `db` fixture (real Postgres) — skipped when no database is reachable.
 its OWN session, so every test COMMITS its setup before calling it.
 """
 
+from app.downloads import quota
 from app.models import DownloadJob, DownloadQuota, MediaAsset, User
 from app.worker import _claim_job
 
@@ -169,3 +170,61 @@ def test_list_downloads_is_capped(db, monkeypatch):
     monkeypatch.setattr(dl, "_MAX_LIST", 2)
     rows = dl.list_downloads(user=u, db=db)
     assert len(rows) == 2  # bounded by the cap, not the 3 rows on disk
+
+
+# --- E12 · S3 · the worker-side max_bytes remainder ------------------------------------------
+
+
+def _sized_asset(db, size_bytes, ref):
+    a = MediaAsset(
+        source_kind="url",
+        source_ref=ref,
+        format_sig="s",
+        status="ready",
+        ref_count=1,
+        size_bytes=size_bytes,
+    )
+    db.add(a)
+    db.flush()
+    return a
+
+
+def test_remaining_bytes_is_none_for_an_unlimited_user(db):
+    u = User(email="unlimited@example.com")
+    db.add(u)
+    db.flush()
+    _quota(db, u.id, max_concurrent=2, unlimited=True)
+    db.flush()
+    # None, not a number: "no cap" and "no budget left" must never be the same value downstream —
+    # build_ydl_opts leaves max_filesize unset for both, so only the caller can tell them apart.
+    assert quota.remaining_bytes(db, u.id) is None
+
+
+def test_remaining_bytes_is_the_unspent_part_of_the_cap(db):
+    u = User(email="partial@example.com")
+    db.add(u)
+    db.flush()
+    db.add(
+        DownloadQuota(user_id=u.id, max_bytes=1000, max_concurrent=2, max_jobs=100, unlimited=False)
+    )
+    a = _sized_asset(db, 400, "partial-1")
+    _job(db, u.id, queue_pos=0, status="done", asset_id=a.id)
+    db.flush()
+    assert quota.remaining_bytes(db, u.id) == 600
+
+
+def test_remaining_bytes_is_zero_once_the_cap_is_met(db):
+    # THE case this exists for: `check_enqueue` let these jobs in while the user was under the cap,
+    # and an earlier one has filled it since. Zero is what makes the worker refuse; if this ever
+    # returned the raw negative or None instead, the user already over quota would be the only one
+    # downloading with no size ceiling at all.
+    u = User(email="atcap@example.com")
+    db.add(u)
+    db.flush()
+    db.add(
+        DownloadQuota(user_id=u.id, max_bytes=1000, max_concurrent=2, max_jobs=100, unlimited=False)
+    )
+    a = _sized_asset(db, 1500, "atcap-1")  # overshot: one job finished larger than the remainder
+    _job(db, u.id, queue_pos=0, status="done", asset_id=a.id)
+    db.flush()
+    assert quota.remaining_bytes(db, u.id) == 0

backend/tests/test_urlguard.py

@@ -85,3 +85,12 @@ def test_non_http_schemes_are_refused_before_any_lookup(monkeypatch, url):
 
 def test_a_url_without_a_host_is_refused():
     assert _blocked_reason("http:///just/a/path") == urlguard.REASON_NO_HOST
+
+
+def test_a_malformed_port_is_a_refusal_not_a_crash(monkeypatch):
+    # `urlparse(...).port` raises ValueError on ACCESS, not at parse time, and `.hostname` returns
+    # first — so an unguarded read turns a user typo into a 500 that escapes the caller's
+    # `except BlockedUrl` and loses the localized detail this module exists to produce.
+    _stub_dns(monkeypatch, ["93.184.216.34"])
+    assert _blocked_reason("http://example.com:99999/v.mp4") == urlguard.REASON_BAD_PORT
+    assert _blocked_reason("http://example.com:abc/v.mp4") == urlguard.REASON_BAD_PORT