When a user hits /new or /resume before the previous session finishes
initializing, session.close runs while the previous session.create's
_build thread is still constructing the agent. session.close pops
_sessions[sid] and closes whatever slash_worker it finds (None at that
point — _build hasn't installed it yet), then returns. _build keeps
running in the background, installs the slash_worker subprocess and
registers an approval-notify callback on a session dict that's now
unreachable via _sessions. The subprocess leaks until process exit;
the notify callback lingers in the global registry.
Fix: _build now tracks what it allocates (worker, notify_registered)
and checks in its finally block whether _sessions[sid] still points
to the session it's building for. If not, the build was orphaned by
a racing close, so clean up the subprocess and unregister the notify
ourselves.
tui_gateway/server.py:
- _build reads _sessions.get(sid) safely (returns early if already gone)
- tracks allocated worker + notify registration
- finally checks orphan status and cleans up
Tests (tests/test_tui_gateway_server.py): 2 new cases.
- test_session_create_close_race_does_not_orphan_worker: slow
_make_agent, close mid-build, verify worker.close() and
unregister_gateway_notify both fire from the build thread's
cleanup path.
- test_session_create_no_race_keeps_worker_alive: regression guard —
happy path does NOT over-eagerly clean up a live worker.
Validated: against the unpatched code, the race test fails with
'orphan worker was not cleaned up — closed_workers=[]'. Live E2E
against the live Python environment confirmed the cleanup fires
exactly when the race happens.
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