fix(uploads): finish the sweeps round 1 left half-done

Deep-review round 2, on round 1's own fix commit. It found MORE than round 1
did (28 raw, against 13), and most of it was mine -- a new piece of UI attracts
findings a backend-only diff never does. The pattern in almost all of them is
the same: a principle applied to the site that prompted it and not to its
siblings.

* `display_text` reached three of the FIVE writers of a user-supplied name.
  `POST /api/downloads` and `POST /api/downloads/edit` still handed Postgres an
  unbounded string, so a 300-character name pasted into the Add-download dialog
  or the editor was a bare 500 (main.py re-raises every DataError but the NUL
  case). Four of the seven reviewers found it independently. The bound now lives
  in `models.py`, the three columns are DECLARED with it, and the guard for the
  next writer is parsed rather than remembered: every `display_name` /
  `display_uploader` assignment under `app/routes/` must go through the helper.
  That guard immediately found two more -- the Google sign-in callback writes
  the profile name into the same 255-wide column -- so it is six, not five.

* The connection release reached one of the THREE routes that read their own
  body. The screenshot route (10 MiB, from a phone) and the client log sink both
  still held a pooled connection idle-in-transaction for the length of the
  upload, which is the invariant db.py sizes the pool on. All three now call
  `db.release_read_connection`, whose precondition -- nothing pending on the
  shared session -- is CHECKED rather than described, because a whole-session
  rollback discarding a caller's staged write is a mistake this repo has already
  made once. `test_body_limit.py` holds the rule for the next such route.

* The AST drift registry keyed its sites by (module, limit expression), so a
  second route copied from the first collapsed onto the same entry and went
  uncovered -- the exact hole the registry exists to close. Keyed per call site
  now, and it carries the release requirement too.

* The dialog's own refusal was announced once and never again: two over-cap
  picks leave an identical node with identical text, and an untouched live
  region says nothing. It is keyed per pick now, the drop zone reads as invalid
  and points at the sentence, and the reason is reachable from the control
  rather than only from a one-shot announcement.

* Two tests rebuilt the blind spot they were written to remove: the dialog's cap
  test sat nowhere near the boundary (a `>` loosened to `>=` survived it, which
  is the mutation round 1 fixed on the server side), and the header-precedence
  test only covered an exact-case duplicate while a differently-cased one would
  have been COMBINED onto the wire rather than replaced. Both fixed, and the
  merge now dedupes case-insensitively because header names are.

Also: the upload dialog's unstubbed usage query was firing a real request from
jsdom in a neighbouring suite and leaking a delayed "connection lost" toast
across test boundaries; `GET /api/downloads/usage` had no test at all though the
whole client-side check hangs off it; and the comment claiming the edge 413 is
readable now says what was measured -- readable to 200 MiB over loopback, a bare
`onerror` through a proxy -- so the pre-send check is named as the mechanism and
that branch as the backstop it is.

Every test added or changed here was mutation-checked. One mutation SURVIVED and
is recorded rather than papered over: the `tooBig` term inside `submit()` cannot
be reached, because `ui/Button` swallows the activation itself, so it is marked
as belt and braces instead of being described as the guard.

backend/app/db.py

@@ -34,3 +34,31 @@ def get_db() -> Iterator[Session]:
         yield db
     finally:
         db.close()
+
+
+def release_read_connection(db: Session) -> None:
+    """End a request's READ transaction so its pooled connection goes back BEFORE a long await.
+
+    SQLAlchemy 2.0 autobegins on the first SELECT, so a request that has merely authenticated is
+    already holding one of the connections above — `idle in transaction` to Postgres, and nothing
+    times it out. A route that then awaits something slow (a request body still arriving, an
+    external fetch) pins it for the whole wait, which is precisely the invariant the pool is sized
+    on in the comment above. Measured: the next checkout after this call reuses the very backend
+    that was released, and a 1.8 s upload goes from one sustained `idle in transaction` to none.
+
+    Every route that reads its own body from a dependency needs this, and `test_body_limit.py`
+    holds that — the three that do are the ones with a raised (or self-imposed) body ceiling, and
+    they got here one at a time, which is how the upload route ended up the only one fixed.
+
+    The caller must have NOTHING PENDING, and that is checked rather than described. The session is
+    shared with every dependency that ran before, so a rollback here would silently discard a write
+    one of them staged — `service.enqueue` already learned that lesson the expensive way and uses a
+    SAVEPOINT for it. CLAUDE.md: a rule stated in a comment must also be enforced in code.
+    """
+    if db.new or db.deleted or db.dirty:
+        raise RuntimeError(
+            "release_read_connection() with pending work: something ahead of this dependency "
+            "staged a write, which ending the transaction would discard. Commit it first, or do "
+            "it after the await."
+        )
+    db.rollback()

backend/app/downloads/pipeline.py

@@ -25,7 +25,7 @@ from app.downloads.jobdb import (
 )
 from app.downloads.stated import StatedFailure
 from app.downloads.status import JobStatus
-from app.models import DownloadJob, MediaAsset
+from app.models import DISPLAY_TEXT_MAX, DownloadJob, MediaAsset
 from app.notifications import create_notification
 from app.titles import normalize_title
 
@@ -597,7 +597,7 @@ def _download(
             }
             if job and not job.display_name and meta.title:
                 # display_name is VARCHAR(255) — clip a long title (see _fill_asset_meta_early).
-                fields["display_name"] = meta.title[:255]
+                fields["display_name"] = meta.title[:DISPLAY_TEXT_MAX]
             # Atomic terminal write: finalizes ONLY while the row is still running, so a child that
             # finishes just after a route cancel/pause can't resurrect it (see finalize_if_running).
             finalized = service.finalize_if_running(db, job_id, **fields)

backend/app/downloads/service.py

@@ -20,7 +20,7 @@ from app.downloads import credentials
 from app.downloads import edit as editmod
 from app.downloads import formats, mediakind, quota, storage
 from app.downloads.status import HOLDING, JobStatus
-from app.models import Channel, DownloadJob, MediaAsset, Video
+from app.models import DISPLAY_TEXT_MAX, Channel, DownloadJob, MediaAsset, Video
 
 
 class EditError(Exception):
@@ -31,26 +31,6 @@ class EditError(Exception):
         super().__init__(reason)
 
 
-# The width of every user-supplied display string on a job (`DownloadJob.display_name`,
-# `display_uploader`): `String(255)`. `test_upload.py` holds this against the columns
-# themselves so the two cannot drift — a number in a comment is exactly how that drift happens.
-DISPLAY_TEXT_MAX = 255
-
-
-def display_text(raw: str | None) -> str | None:
-    """A user-supplied display string on its way into one of those columns: stripped, truncated,
-    blank → None.
-
-    One definition because there are three writers and they had drifted: the metadata PATCH
-    truncated, the upload ingest did not, and since P1 the upload's name arrives in a REQUEST HEADER
-    where nothing bounds its length — so a long enough one reached Postgres as a `DataError`, i.e. a
-    500 after the whole file had already been transferred. Truncating is the right answer rather
-    than refusing: the name is a label on a file the user has already sent, and losing the tail of it
-    is not worth failing the upload over.
-    """
-    return (raw or "").strip()[:DISPLAY_TEXT_MAX] or None
-
-
 def source_url(source_kind: str, source_ref: str) -> str:
     """The URL yt-dlp should fetch. YouTube stores the 11-char id (the adapter reconstructs the watch
     URL); ad-hoc sources store the URL verbatim."""
@@ -199,7 +179,7 @@ def enqueue(
         profile_id=profile_id,
         profile_snapshot=spec,
         display_name=display_name
-        or (asset.title[:255] if asset.status == "ready" and asset.title else None),
+        or (asset.title[:DISPLAY_TEXT_MAX] if asset.status == "ready" and asset.title else None),
         status="queued",
         queue_pos=next_queue_pos(db),
     )
@@ -218,10 +198,13 @@ def enqueue(
 
 
 def _clip_title(source_title: str | None, display_name: str | None) -> str:
+    # Clipped to DISPLAY_TEXT_MAX, not to a literal: this feeds `DownloadJob.display_name` through
+    # `enqueue_edit`, the same column `display_text` guards. A machine-made title, so it is clipped
+    # rather than run through `display_text` — blank here means "no title", not None.
     if display_name:
-        return display_name[:255]
+        return display_name[:DISPLAY_TEXT_MAX]
     base = source_title or "Clip"
-    return f"{base} (clip)"[:255]
+    return f"{base} (clip)"[:DISPLAY_TEXT_MAX]
 
 
 def enqueue_edit(
@@ -275,7 +258,7 @@ def enqueue_edit(
         source_asset_id=src_asset.id,
         edit_spec=spec,
         profile_snapshot={},
-        display_name=display_name or asset.title,
+        display_name=display_name or asset.title[:DISPLAY_TEXT_MAX],
         status="queued",
         queue_pos=next_queue_pos(db),
     )

backend/app/downloads/upload.py

@@ -25,7 +25,7 @@ from sqlalchemy.orm import Session
 from app.config import settings
 from app.downloads import edit as editmod
 from app.downloads import mediakind, probe, quota, service, storage
-from app.models import DownloadJob, MediaAsset
+from app.models import DownloadJob, MediaAsset, display_text
 
 
 def _title_from_filename(filename: str) -> str:
@@ -99,7 +99,7 @@ def ingest_upload(
             source_kind="upload",
             source_ref=ref,
             profile_snapshot={},
-            display_name=service.display_text(display_name),
+            display_name=display_text(display_name),
             status="done",
             progress=100,
             queue_pos=service.next_queue_pos(db),

backend/app/models.py

@@ -23,6 +23,34 @@ from sqlalchemy.dialects.postgresql import JSONB, TSVECTOR
 from sqlalchemy.orm import Mapped, mapped_column, relationship, validates
 
 from app.db import Base
+
+# Every user-supplied display string in this schema shares one width, and it lives HERE so the
+# columns below are declared with it rather than with a literal: a name a person typed goes into
+# `User.display_name` (their Google profile name), `DownloadJob.display_name` and
+# `DownloadJob.display_uploader`. A value wider than the column is a psycopg DataError, which
+# `main.py` re-raises for everything but the NUL case — i.e. a bare 500 for a name somebody pasted.
+DISPLAY_TEXT_MAX = 255
+
+
+def display_text(raw: str | None) -> str | None:
+    """A user-supplied display string on its way into one of those columns: stripped, truncated,
+    blank -> None.
+
+    One definition because there are SIX writers and they had drifted: `POST /api/downloads`,
+    `POST /api/downloads/edit`, `POST /api/downloads/upload`, the metadata PATCH's two fields, and
+    the Google sign-in callback. Only the PATCH truncated. Truncating is the right answer rather
+    than refusing: the name is a label on work the user has already done — a file already
+    transferred, an account already authenticated — and losing its tail is not worth failing the
+    request over.
+
+    `test_upload.py` holds both halves: that every route assigning one of these fields goes through
+    this helper (parsed, not grepped), and that each of those routes truncates rather than 500s. A
+    sweep is exactly the kind of thing that gets done five-sixths of the way, which is how this
+    ended up being written twice.
+    """
+    return (raw or "").strip()[:DISPLAY_TEXT_MAX] or None
+
+
 from app.utils import canonical_email
 
 
@@ -114,7 +142,7 @@ class User(Base, TimestampMixin, CanonicalEmailMixin):
     # not cleared eagerly — it simply stops counting).
     diagnostics_level: Mapped[str | None] = mapped_column(String(8))
     diagnostics_until: Mapped[datetime | None] = mapped_column(DateTime(timezone=True))
-    display_name: Mapped[str | None] = mapped_column(String(255))
+    display_name: Mapped[str | None] = mapped_column(String(DISPLAY_TEXT_MAX))
     avatar_url: Mapped[str | None] = mapped_column(String(1024))
     role: Mapped[str] = mapped_column(String(16), default="user", server_default="user")
     # The user's own YouTube channel id, resolved lazily (channels.list?mine=true) and
@@ -953,11 +981,11 @@ class DownloadJob(Base, TimestampMixin, UpdatedAtMixin):
         ForeignKey("download_profiles.id", ondelete="SET NULL")
     )
     profile_snapshot: Mapped[dict] = mapped_column(JSON)
-    display_name: Mapped[str | None] = mapped_column(String(255))
+    display_name: Mapped[str | None] = mapped_column(String(DISPLAY_TEXT_MAX))
     # Per-user display overrides + extras (like display_name — metadata only, never the file).
     # `display_uploader`/`display_uploader_url` override the asset's auto channel name/link;
     # `extra_links` is an optional list of extra reference URLs shown on the card + watch page.
-    display_uploader: Mapped[str | None] = mapped_column(String(255))
+    display_uploader: Mapped[str | None] = mapped_column(String(DISPLAY_TEXT_MAX))
     display_uploader_url: Mapped[str | None] = mapped_column(Text)
     extra_links: Mapped[list | None] = mapped_column(JSON)
     status: Mapped[str] = mapped_column(

backend/app/routes/auth.py

@@ -39,7 +39,7 @@ from app.auth import (
 )
 from app.config import settings
 from app.db import SessionLocal, get_db
-from app.models import AuthToken, DemoWhitelist, Invite, OAuthToken, User
+from app.models import AuthToken, DemoWhitelist, Invite, OAuthToken, User, display_text
 from app.ratelimit import RateLimiter, client_key
 from app.security import encrypt, hash_password, hash_token, verify_password
 from app.utils import canonical_email, valid_email
@@ -472,7 +472,7 @@ async def callback(
     if email:
         user.google_email = email
     _sync_google_email(db, user, email)
-    user.display_name = userinfo.get("name")
+    user.display_name = display_text(userinfo.get("name"))
     user.avatar_url = userinfo.get("picture")
     # ADMIN_EMAILS (env) is the bootstrap admin list and always wins, so the configured admin can't
     # be locked out. Everyone else's role is managed in the admin UI and stored in the DB, so a
@@ -594,7 +594,7 @@ def _complete_link(
     if linked_email:
         user.google_email = linked_email  # see the sign-in callback: the other half of the identity
     if not user.display_name:
-        user.display_name = userinfo.get("name")
+        user.display_name = display_text(userinfo.get("name"))
     if not user.avatar_url:
         user.avatar_url = userinfo.get("picture")
     _store_token(db, user, token)

backend/app/routes/debug_sessions.py

@@ -22,7 +22,7 @@ from sqlalchemy.orm import Session
 from app import audit, debugsession, logs, logsink
 from app.audit import AuditAction
 from app.auth import require_human
-from app.db import get_db
+from app.db import get_db, release_read_connection
 from app.issues import bundle, gitea
 from app.ratelimit import RateLimiter
 from app.refusal import refused
@@ -335,7 +335,13 @@ def _upload_target(
     return owned_or_404(db, DebugSession, sid, user, what="debug_session")
 
 
-async def _image_body(request: Request) -> bytes:
+async def _image_body(request: Request, db: Session = Depends(get_db)) -> bytes:
+    # The owner check above has already run, and it was a SELECT — so this session is holding a
+    # pooled connection `idle in transaction` and would hold it for the whole 10 MiB upload, from a
+    # client that may be on a phone. Hand it back first; the handler's own work re-takes one. The
+    # `session` object the handler holds is expired by this and reloads on its next attribute read,
+    # which is the correct moment to touch the database again.
+    release_read_connection(db)
     return await capped_body(request, debugsession.SCREENSHOT_MAX_BYTES)
 
 

backend/app/routes/diagnostics.py

@@ -31,7 +31,7 @@ from sqlalchemy.orm import Session
 
 from app import debugsession, diagnostics, logs, logsink
 from app.auth import current_user
-from app.db import get_db
+from app.db import get_db, release_read_connection
 from app.models import DebugSession, LogEvent, User
 from app.ratelimit import RateLimiter
 from app.routes._common import capped_body
@@ -73,7 +73,7 @@ class ClientEventsIn(BaseModel):
     events: list[ClientEvent] = Field(max_length=EVENTS_MAX)
 
 
-async def _parsed_events(request: Request) -> ClientEventsIn:
+async def _parsed_events(request: Request, db: Session = Depends(get_db)) -> ClientEventsIn:
     """The body as the model — parsed only after the size cap, which is why this is a dependency and
     not a plain body parameter (FastAPI reads a declared body in full before anything else runs).
 
@@ -83,6 +83,10 @@ async def _parsed_events(request: Request) -> ClientEventsIn:
     media_type = request.headers.get("content-type", "").split(";")[0].strip().lower()
     if media_type != "application/json" and not media_type.endswith("+json"):
         raise HTTPException(status_code=415, detail={"code": "json_required"})
+    # `current_user` resolved above on a SELECT, so this session is holding a pooled connection.
+    # Give it back before awaiting the body — the sink is a background beacon and its sender may be
+    # on a link far slower than the 512 KiB suggests. See `db.release_read_connection`.
+    release_read_connection(db)
     raw = await capped_body(request, BODY_MAX_BYTES)
     try:
         return ClientEventsIn.model_validate_json(raw)

backend/app/routes/downloads.py

@@ -24,7 +24,7 @@ from sqlalchemy.orm import Session
 from app import audit, sysconfig
 from app.auth import admin_user, require_human
 from app.config import settings
-from app.db import get_db
+from app.db import get_db, release_read_connection
 from app.downloads import credentials as dlcreds
 from app.downloads import edit as editmod
 from app.downloads import links as linksmod
@@ -39,6 +39,7 @@ from app.models import (
     DownloadShare,
     MediaAsset,
     User,
+    display_text,
 )
 from app.routes._common import capped_stream_to, get_or_404, not_found, owned_or_404
 from app.security import hash_password
@@ -400,7 +401,7 @@ def enqueue_download(
                 status_code=422, detail={"code": "url_blocked", "reason": e.reason}
             ) from e
     spec, profile_id = _resolve_spec(db, user, body.profile_id, body.spec)
-    display_name = (body.display_name or "").strip() or None
+    display_name = display_text(body.display_name)
     try:
         job = service.enqueue(db, user.id, source_kind, source_ref, spec, profile_id, display_name)
     except quota.QuotaExceeded as e:
@@ -463,17 +464,11 @@ async def spool_upload(
     empty, quota, probe or move error, a client that vanished mid-upload — it is removed."""
     cap = sysconfig.get_int(db, "download_upload_max_bytes")
     user_id = user.id
-    # Hand the pooled connection back BEFORE the transfer starts. Resolving `user` and reading the
-    # cap were both SELECTs, and SQLAlchemy 2.0 autobegins a transaction on the first one — so
-    # without this the session sits `idle in transaction` holding one of the twenty pooled
-    # connections for as long as the client cares to keep sending. That is the invariant `db.py`
-    # sizes the pool on, and `plex/playback.py` records the production incident that taught it;
-    # reading the body here instead of letting FastAPI spool it (P1) is what put this route at risk
-    # of breaking it. Auth only reads, so ending the read transaction loses nothing, and the
-    # handler's first query autobegins a fresh one — one ROLLBACK round-trip against a minute of
-    # held connection. Everything this dependency still needs is already an int in hand: touching
-    # an ORM attribute below would reload `user` and check a connection straight back out.
-    db.rollback()
+    # Hand the pooled connection back BEFORE the transfer starts — see `db.release_read_connection`
+    # for why, and for the precondition it enforces. Everything this dependency still needs is
+    # already an int or a header in hand: touching an ORM attribute below would reload `user` and
+    # check a connection straight back out.
+    release_read_connection(db)
     staging = Path(settings.download_root) / ".staging" / "uploads"
     staging.mkdir(parents=True, exist_ok=True)
     fd, tmp = tempfile.mkstemp(dir=str(staging))
@@ -491,7 +486,7 @@ async def spool_upload(
             size=size,
             user_id=user_id,
             filename=_header_text(request, UPLOAD_FILENAME_HEADER) or "upload",
-            display_name=service.display_text(_header_text(request, UPLOAD_DISPLAY_NAME_HEADER)),
+            display_name=display_text(_header_text(request, UPLOAD_DISPLAY_NAME_HEADER)),
         )
     finally:
         tmp_path.unlink(missing_ok=True)
@@ -546,7 +541,7 @@ def enqueue_edit(
     if source_job.status != "done" or source_job.asset_id is None:
         raise refused(409, "edit_unfinished")
     spec = body.edit_spec
-    display_name = (body.display_name or "").strip() or None
+    display_name = display_text(body.display_name)
     try:
         job = service.enqueue_edit(db, user.id, source_job, spec, display_name)
     except quota.QuotaExceeded as e:
@@ -690,9 +685,9 @@ def update_download_meta(
     job = owned_or_404(db, DownloadJob, job_id, user, what="download")
     sent = body.model_fields_set
     if "display_name" in sent:
-        job.display_name = service.display_text(body.display_name)
+        job.display_name = display_text(body.display_name)
     if "display_uploader" in sent:
-        job.display_uploader = service.display_text(body.display_uploader)
+        job.display_uploader = display_text(body.display_uploader)
     if "display_uploader_url" in sent:
         job.display_uploader_url = _clean_url(body.display_uploader_url)
     if "extra_links" in sent:

backend/app/worker.py

@@ -43,7 +43,7 @@ from app.downloads.jobdb import (
     _staging_dir,
 )
 from app.downloads.status import STOPPED_BY_ROUTE, JobStatus
-from app.models import DownloadJob, MediaAsset
+from app.models import DISPLAY_TEXT_MAX, DownloadJob, MediaAsset
 
 log = logs.get_logger(__name__)
 _stop = threading.Event()
@@ -562,7 +562,7 @@ def _finish_from_cache(job_id: int, asset_id: int) -> None:
             fields = {"status": JobStatus.DONE, "progress": 100, "phase": None}
             if not job.display_name and asset.title:
                 # display_name is VARCHAR(255); a title can be longer (e.g. a recipe in the title).
-                fields["display_name"] = asset.title[:255]
+                fields["display_name"] = asset.title[:DISPLAY_TEXT_MAX]
             asset.last_access_at = datetime.now(timezone.utc)
             # Atomic finalize: only marks the job done while it is still running, so a concurrent
             # cancel/pause is never resurrected (see service.finalize_if_running).