Reported 2026-09-27: click avatar -> Change Account -> cancel in the Google
chooser -> back to a signed-out app, then "cannot sign-in because the callback
url was not released".
Two independent defects:
1. ChangeAccountAsync ran `await SignOutYouTubeAsync(); await SignInAsync();`.
SignOutYouTubeAsync -> TokenStore.Clear() -> deletes ytLlive.auth, so the
working account's token was destroyed before the browser even opened. It is
now just `await SignInAsync()`: success overwrites the token via the
sessionChanged hook, cancel/failure keeps the current session. The explicit
sign-out was never needed.
2. Abandoning the browser gives the app no signal, so the OAuth attempt held
localhost:8765 for its full 5-minute timeout and a retry could not bind. A
new AuthenticateAsync now cancels and awaits the abandoned attempt first.
That takeover is serialised by a SemaphoreSlim: the first version cleared
the in-flight marker before awaiting, so a caller arriving in that window saw
a free port and raced to bind it -- reproducing the very failure it was
written to prevent. My own test caught that; reasoning had "proved" it fine.
Also adds an `openBrowser` ctor seam so tests never shell out to a real
browser, and corrects the ai.md line that documented "Logout / Change Account ->
SignOutYouTubeAsync" as intended behaviour.
Test: YouTubeAuthServiceTests.RetryingAfterAnAbandonedAttempt_ReleasesTheCallbackPort
Full suite 370/370, 0 warnings. Coverage gap noted in HANDOFF.md: the ordering
fix has no automated test because _youtubeAuth is hardcoded in MainViewModel
and ChangeAccountAsync is private.
The reported cross-instance effect is NOT this cause and stays open -- no code
path can sign out a second instance (per-instance TokenStore, local delete, no
server-side revoke).
gramps
44344c9327