## Observed bug
Anna's Archive slow-download pages can return a JavaScript countdown
before a download link is available. The internal browser returns that
waiting-room HTML and closes its incognito session. The downloader then
sleeps and fetches the URL again, which can create a new queue session
and **restart the countdown instead of reaching the download link**.
## Fix
- **Preserve the queue session:** keep the original browser tab open
while the site's own countdown and automatic navigation finish. HTTP 200
and cached-cookie waiting-room responses enter the same flow.
- **Return a consistent page:** capture HTML and readiness together in
one browser evaluation so navigation cannot pair a new page's status
with stale protection-page HTML. Share cache validation and
page-readiness rules across their callers.
- **Keep waiting cancellable and bounded:** poll cancellation while a
slow browser read remains pending, rather than repeatedly cancelling and
reissuing it. Apply a **300-second waiting-room limit** within the
existing browser watchdog.
- **Report queue timeouts accurately:** preserve the timeout across the
helper-process boundary and stop the solve without restarting the
browser or rotating mirrors.
Waiting-room detection is limited to Anna's Archive `/slow_download/`
pages containing an actual `.js-partner-countdown` element. The site
controls the countdown and refresh. External-bypasser behavior and
file-transfer timeouts are unchanged; the PR adds no deployment
configuration or dependencies.
## Validation
Validated at `c81e0a2`:
| Check | Result |
| --- | --- |
| Full Linux unit suite | **2,978 passed** on Python 3.14 in a non-root
environment with entrypoint test stubs enabled |
| Focused regression coverage | **30 passed**, covering countdown
completion, zero timers, navigation, both cookie-cache paths,
cancellation, stuck queues, slow reads, and timeout propagation |
| Navigation-race regression | Fails against the previous PR
implementation and passes with the fix |
| Python static checks | Ruff lint/format, BasedPyright for backend and
tests, and Vulture passed |
| Real Chromium fixture | Queue cookie persisted through 1.5-second DOM
reads and one automatic refresh; the CDP connection survived multiple
polling intervals |
| Live source check | Observed **19 → 14 → 9 → 4 → download link** while
retaining the browser session; the patched browser path also completed
the waiting room |
Full unit-suite command:
```sh
pytest tests/ -n 2 --tb=short -m "not integration and not e2e"
```
The live check validates waiting-room completion and link resolution.
Remote file-host availability remains a separate concern. The unit suite
emitted two existing Authlib deprecation warnings.
