_handle_active_session_busy_message (the busy_session_handler most
platform adapters register) demotes busy_input_mode='interrupt' to
queue semantics for two reasons: active subagents (#30170) and, as of
this week, context compression in flight (#56391) — interrupting while
compression holds the state.db lock races a new turn against the
pre-rotation parent session, and if that new turn also grows past the
compression threshold it starts its own uncancellable compression on
the same stale parent, forking orphaned compression siblings.
_handle_message has its own, independent inline "PRIORITY" busy-path
(reached directly with a live running agent — see the `if _quick_key in
self._running_agents:` guard, exercised end-to-end by the existing
tests/gateway/test_running_agent_session_toggles.py harness). Its own
comment says it mirrors _handle_active_session_busy_message's subagent-
demotion rationale verbatim, and it does demote for active subagents,
but it never checked _session_has_compression_in_flight, so a plain-text
follow-up landing on this path while compression is mid-flight still
called running_agent.interrupt() unconditionally.
Fix: add the same _session_has_compression_in_flight(session_key) check
before the PRIORITY interrupt call, demoting to queue exactly like the
sibling path.
Tests: tests/gateway/test_priority_path_compression_demotion_56391.py
drives _handle_message end-to-end (reusing the test_running_agent_
session_toggles.py harness pattern) with a live running agent and a
mocked compression lock. Mutation-verified: reverting the fix makes the
demotion test fail (interrupt() gets called) against the pre-fix code;
a control test pins the unchanged default-interrupt behavior when no
compression lock is held.
pierrenode
d33becd877