fix(r5): address the eighth /code-review high round — 7 findings

The worst one was, again, the previous round's own fix.

- Round 7 stopped awaiting the HLS sweep so startup could serve immediately — which
  also made it run CONCURRENTLY with playback, and `sweep_orphans` snapshotted the
  live-session set BEFORE listing the root and rmtree'd outside the lock. Since
  `start_session` reuses a directory path for the same (key, offset, tag), a stale
  name can become a live session at any moment. Two guards now: nothing whose mtime
  is newer than this process's start is ever deleted, and the live check + rmtree
  happen together under the lock, one directory at a time.
- The sweep task is awaited after cancel, so shutdown can't leave it pending.
- `_rate_limiter` used a truthiness test on its timestamp, so a `now()` of exactly
  0.0 read as "never ran" — unreachable in production, but `now` exists to be
  injected and a test clock starting at 0 is the obvious choice.
- The RSS total-outage error now carries the first underlying error: "all N channels
  failed" is also what ONE dead feed id looks like on a small instance, and a red
  card the user can't act on is its own kind of dishonest.
- The WebKit fullscreen handling moved into `lib/fullscreen` and PlexPlayer uses it
  too — it had the same unprefixed-only reads in three places, including an Escape
  branch that would have closed the whole player instead of leaving fullscreen.
- The `--max` CSS comment claimed `inset: 0` did the sizing; Tailwind's `w-full` is
  still on the element and wins. Comment now states the real mechanism.

Verified in real Chrome (the pane can't composite or do native fullscreen):
- F fills the 1920x889 viewport; the exit pill renders top-right on the letterbox
  band and overlaps NO YouTube control — the collision this round suspected does not
  reproduce in this embed (its own buttons sit bottom-left / bottom-right).
- Four real ArrowDown presses while maximised: persisted volume 100 -> 80, with the
  level flash visible on screen.
- A real click on the exit pill un-maximises and returns focus to the card.
- lib/fullscreen driven from a real click: enter (innerHeight 889 -> 1024), the
  change listener fires exactly once per transition, exit returns to 889.

Backend suite 150 -> 158; the new sweep tests are mutation-checked, and they read
their cutoff from the filesystem rather than a clock (the container VM and the
bind-mounted host disagree by enough to make a clock-based assertion flaky).

backend/app/main.py

@@ -1,7 +1,7 @@
 import asyncio
 import logging
 import sys
-from contextlib import asynccontextmanager
+from contextlib import asynccontextmanager, suppress
 from pathlib import Path
 
 from fastapi import FastAPI, HTTPException
@@ -82,7 +82,13 @@ async def lifespan(app: FastAPI):
         yield
     finally:
         log.info("Siftlode shutting down")
+        # Awaited, not just cancelled: a bare `.cancel()` lets the loop close with the task still
+        # pending ("Task was destroyed but it is pending!" — noise that reads like a bug during
+        # triage). Cancelling does NOT interrupt the rmtree thread itself; this only makes our own
+        # bookkeeping honest.
         sweep.cancel()
+        with suppress(asyncio.CancelledError):
+            await sweep
         shutdown_scheduler()
 
 

backend/app/plex/stream.py

@@ -47,6 +47,10 @@ _SESSION_IDLE_S = 600  # reap a session with no access for this long
 # fail. Covered by test_plex_stream.py — this regex is the only thing standing between the sweep
 # and someone else's data.
 _SESSION_DIR_RE = re.compile(r"^\d+_\d+(_[^_]+_[+-]\d+\.\d{2})?$")
+# 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
+# for the same (rating_key, offset, tag), "stale name" is not the same as "stale directory".
+_PROCESS_START = time.time()
 
 _lock = threading.Lock()
 _sessions: dict[str, "HlsSession"] = {}
@@ -268,7 +272,7 @@ def wait_for(path: Path, timeout: float = 20.0) -> bool:
     return path.exists()
 
 
-def sweep_orphans() -> int:
+def sweep_orphans(older_than: float | None = None) -> int:
     """Delete OUR segment directories that no live session owns.
 
     Sessions live only in THIS process, so at startup every session directory under `_HLS_ROOT` is
@@ -278,18 +282,39 @@ def sweep_orphans() -> int:
 
     Only entries whose name matches `_SESSION_DIR_RE` are touched: the root is admin-configurable,
     so anything else under it belongs to someone else and is left alone. Blocking (rmtree) — call
-    it off the event loop."""
-    with _lock:
-        live = {s.dir for s in _sessions.values()}
+    it off the event loop.
+
+    TWO guards against deleting a LIVE session, because this now runs CONCURRENTLY with request
+    handling (the caller stopped awaiting it so startup isn't held up):
+    * `older_than` (default: this process's start) — a directory touched since we booted was made
+      by THIS run, so it is by definition not a leftover. This is the guard that matters, because
+      `start_session` REUSES the same path for the same (key, offset, tag): a stale directory can
+      become a live one at any moment.
+    * the live-session check and the rmtree happen together under `_lock`, so a session can't be
+      registered in the gap between them. The lock is held for one directory at a time — long
+      enough to be atomic, short enough that a boot-time sweep of a big backlog doesn't stall
+      playback."""
+    cutoff = _PROCESS_START if older_than is None else older_than
     dropped = 0
     try:
         entries = list(_HLS_ROOT.iterdir())
     except OSError:  # the root doesn't exist yet — nothing to sweep
         return 0
     for p in entries:
-        if p.is_dir() and p not in live and _SESSION_DIR_RE.match(p.name):
+        if not _SESSION_DIR_RE.match(p.name):
+            continue
+        if not p.is_dir():
+            continue
+        try:
+            if p.stat().st_mtime >= cutoff:
+                continue  # this run made (or reused) it — never ours to delete
+        except OSError:  # vanished under us (a concurrent restart of that session)
+            continue
+        with _lock:
+            if any(s.dir == p for s in _sessions.values()):
+                continue
             shutil.rmtree(p, ignore_errors=True)
-            dropped += 1
+        dropped += 1
     return dropped
 
 

backend/app/sync/runner.py

@@ -60,13 +60,19 @@ def run_rss_poll(db: Session, channels: list[Channel] | None = None) -> dict[str
 
     Raises RuntimeError when NOTHING could be polled (`failed == total`, total > 0): a run that
     achieved literally nothing is a failed run, and only an exception turns the scheduler card red
-    — a returned count leaves it green with the outage buried in the summary line."""
+    — a returned count leaves it green with the outage buried in the summary line. The message
+    carries the FIRST underlying error, because on a small instance "all channels failed" is also
+    what a single dead feed id looks like."""
     if channels is None:
         channels = db.execute(select(Channel)).scalars().all()
     total = len(channels)
     new = 0
     done = 0
     failed = 0
+    # Kept for the total-outage message: "failed for all N channels" alone can't tell an egress
+    # outage from one permanently dead feed id — which is the whole difference on an instance with
+    # a single subscription, where BOTH render as 100% failed.
+    first_error: str | None = None
     # Fetch feeds concurrently (network-bound, no DB), then apply inserts on this thread as
     # each fetch returns — a SQLAlchemy session isn't thread-safe. Pass the channel id (a
     # plain str) to the workers; the ORM instance is touched only here on the main thread.
@@ -86,17 +92,20 @@ def run_rss_poll(db: Session, channels: list[Channel] | None = None) -> dict[str
             except RssError as exc:
                 log.warning("RSS poll skipped for channel %s: %s", channel.id, exc)
                 failed += 1
-            except Exception:
+                first_error = first_error or f"{channel.id}: {exc}"
+            except Exception as exc:
                 log.exception("RSS fetch failed for channel %s", channel.id)
                 failed += 1
+                first_error = first_error or f"{channel.id}: {exc}"
             else:
                 try:
                     new += apply_rss_feed(db, channel, entries)
-                except Exception:
+                except Exception as exc:
                     # A write failure (read-only DB, failover) leaves the channel just as un-polled
                     # as an unreachable feed — count it, or a wholly broken run reports "failed=0".
                     db.rollback()
                     failed += 1
+                    first_error = first_error or f"{channel.id} (apply): {exc}"
                     log.exception("RSS apply failed for channel %s", channel.id)
             # One place that advances the counter, whatever happened above.
             done += 1
@@ -106,9 +115,12 @@ def run_rss_poll(db: Session, channels: list[Channel] | None = None) -> dict[str
     if total and failed == total:
         # Nothing was polled at all — an egress outage (the tinyproxy-after-reboot incident), a
         # dead DNS, a read-only database. Returning normally would record the run as `ok` with the
-        # failure hidden inside the result string, i.e. a green pill for a total outage; the count
-        # in the message keeps the summary just as informative.
-        raise RuntimeError(f"RSS poll failed for all {total} channels")
+        # failure hidden inside the result string, i.e. a green pill for a total outage.
+        # The first error TRAVELS WITH the message on purpose: on an instance with one or two
+        # subscriptions "all channels failed" is also what ONE dead feed id looks like, and a red
+        # card the user can't act on is its own kind of dishonest. `channel: HTTP 404` says
+        # "fix this subscription"; `Connection refused` says "the egress is down".
+        raise RuntimeError(f"RSS poll failed for all {total} channels — first: {first_error}")
     return {"new": new, "failed": failed}
 
 

backend/app/worker.py

@@ -330,11 +330,17 @@ _CANCEL_POLL_INTERVAL_S = 1.0
 def _rate_limiter(interval_s: float, *, now=time.monotonic):
     """`should_run()` → True at most once per `interval_s` (the first call always passes).
     `now` is injectable so tests drive a clock instead of patching the global one."""
-    state = {"at": 0.0}
+    # `None`, not 0.0: "never ran" has to be a VALUE, not a falsy timestamp. A truthiness test here
+    # reads a legitimate `now() == 0.0` as "never ran" and lets a second call straight through —
+    # unreachable with real `time.monotonic()`, but `now` exists to be injected, and a test clock
+    # starting at 0 is the obvious choice. That would let a throttle test encode the wrong
+    # behaviour and still pass.
+    state: dict[str, float | None] = {"at": None}
 
     def should_run() -> bool:
         t = now()
-        if state["at"] and t - state["at"] < interval_s:
+        last = state["at"]
+        if last is not None and t - last < interval_s:
             return False
         state["at"] = t
         return True