`_process_message_background` finished a turn, found a queued
follow-up, and drained it via `await
self._process_message_background(pending_event, session_key)`. Each
chained follow-up added a frame to the call stack instead of starting
fresh. Under sustained pending-queue activity (e.g. a user sending
follow-ups faster than the agent finishes turns) the C stack would
exhaust at ~2000 nested frames and SIGSEGV the process.
Mirror the late-arrival drain pattern that already exists in the same
function: spawn a new `asyncio.create_task(...)` for the pending event
and return so the current frame can unwind. The new task takes
ownership via `_session_tasks[session_key]`.
The late-arrival drain in `finally` could now race with the in-band
drain across the `await typing_task` / `await stop_typing` window, so
add a guard: if `_session_tasks[session_key]` is no longer the current
task, an in-band drain already spawned a follow-up task — re-queue the
late-arrival event so that task picks it up after its current event,
instead of spawning a second concurrent task for the same session_key.
Regression test (`test_pending_drain_no_recursion.py`) chains 12
follow-ups and asserts the recorded
`_process_message_background` stack depth stays bounded at handler
entry. Pre-fix: depths grow linearly `[1,2,3,…,12]`. Post-fix: all
depths are `1`.
`test_duplicate_reply_suppression::test_stale_response_suppressed_when_interrupted`
called `_process_message_background` directly and implicitly relied on
the old recursive `await` semantic — updated to wait for the spawned
drain task before checking the sent list.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
When a model (e.g. mimo-v2-pro) streams intermediate text alongside tool
calls ("Let me search for that") but then returns empty after processing
tool results, the stream consumer already_sent flag is True from the
earlier text delivery. The gateway suppression check
(already_sent=True, failed=False → return None) would swallow the final
response, leaving the user staring at silence after the search.
Two changes:
1. gateway/run.py return path: skip already_sent suppression when the
final_response is "(empty)" or empty — the user needs to know the
agent finished even if streaming sent partial content earlier.
2. gateway/run.py response handler: convert the internal "(empty)"
sentinel to a user-friendly warning instead of delivering the raw
sentinel string.
Tests added for all empty/None/sentinel cases plus preserved existing
suppression behavior for normal non-empty responses.
Three fixes for the duplicate reply bug affecting all gateway platforms:
1. base.py: Suppress stale response when the session was interrupted by a
new message that hasn't been consumed yet. Checks both interrupt_event
and _pending_messages to avoid false positives. (#8221, #2483)
2. run.py (return path): Remove response_previewed guard from already_sent
check. Stream consumer's already_sent alone is authoritative — if
content was delivered via streaming, the duplicate send must be
suppressed regardless of the agent's response_previewed flag. (#8375)
3. run.py (queued-message path): Same fix — already_sent without
response_previewed now correctly marks the first response as already
streamed, preventing re-send before processing the queued message.
The response_previewed field is still produced by the agent (run_agent.py)
but is no longer required as a gate for duplicate suppression. The stream
consumer's already_sent flag is the delivery-level truth about what the
user actually saw.
Concepts from PR #8380 (konsisumer). Closes#8375, #8221, #2483.
