First module of the tool/ coverage task. It is the one the task was raised
for: _start_callback_server's runtime path had never been exercised, and it
is the only tool/ module with no network dependency, so it needs no mocking.
Driven over real HTTP against 127.0.0.1 on a port the module picks, rather
than with a faked request object. The branches worth protecting only exist
once a socket is involved -- particularly the /favicon.ico fetch that must be
answered without being recorded, since treating it as the callback retires the
server before Google ever redirects and surfaces to the user as a consent
timeout. Both serve-loop exits are covered: a result arriving, and the
deadline passing (monkeypatched negative rather than waiting out 300s).
Writing them surfaced a teardown race, not a bug in the module: calling
server_close() while the worker is still inside handle_request() pulls the
socket out from under it and raises on the thread. Invisible normally and
deterministic under --cov, whose tracer widens the window -- so the tests
retire the thread through the loop's own exit condition before closing, via
one _retire helper. Verified over 6 consecutive --cov runs.
crdt_sync 259 -> 268 passed, still 100%. tool/ is not yet in the coverage
source, so the config flip stays last, per the prompt.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01CFSGeWxHPY5rHUGrPqhcmG
