Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@src/app/endpoints/streaming_query.py`:
- Around line 483-485: The compaction-path except block yields
http_exception_stream_event(e) without preserving the negotiated media type,
causing text-mode errors to lose plain-text formatting; update the except
handler in streaming_query.py to pass the negotiated media type into the
formatter (e.g., call http_exception_stream_event(e, media_type) or route this
branch through stream_http_error_event(e, media_type)) so MEDIA_TYPE_TEXT
requests get the same media-type-aware error shape as the non-compaction path.

In `@src/utils/stream_interrupt.py`:
- Around line 35-43: Update type hints and docstrings in
src/utils/stream_interrupt.py: replace all uses of Optional[ResponseInput] with
the modern union ResponseInput | None (including signatures of
persist_interrupted_turn and register_interrupt_callback) and remove the
Optional import; add Google-style docstring sections (Parameters, Returns,
Raises) for background_update_topic_summary,
shutdown_background_topic_summary_tasks, persist_interrupted_turn, and
register_interrupt_callback (ensure register_interrupt_callback documents the
Raises clause), and add a short docstring for the nested async def
on_interrupt() -> None explaining its purpose and exceptions; keep identifiers
intact (background_update_topic_summary,
shutdown_background_topic_summary_tasks, persist_interrupted_turn,
register_interrupt_callback, on_interrupt) so reviewers can locate the changes.

In `@src/utils/streaming_sse.py`:
- Around line 27-29: The type annotation for the media_type parameter in
stream_http_error_event uses Optional[str]; update it to the modern union syntax
str | None (i.e., change "media_type: Optional[str] = MEDIA_TYPE_JSON" to
"media_type: str | None = MEDIA_TYPE_JSON") and remove any now-unnecessary
Optional import if present; keep the function name stream_http_error_event and
default value MEDIA_TYPE_JSON unchanged.

In `@tests/unit/utils/test_stream_interrupt.py`:
- Around line 114-115: Replace the fragile fixed sleep (await
asyncio.sleep(0.01)) with an explicit completion mechanism: have the test wait
for the actual work to finish by either awaiting the spawned task, waiting on an
asyncio.Event set by the background callback, or draining
utils.stream_interrupt.background_topic_summary_tasks (e.g., await all tasks in
that set) so the assertion only runs after the consumer/callback has completed;
update the spots mentioned (around lines with await asyncio.sleep, and similarly
at the other locations noted) to use one of these explicit waits and ensure the
cancelled consumer task is awaited/joined instead of relying on time-based
sleeps.
- Around line 188-193: The test uses AsyncMock instances but asserts them with
sync assertions; change append_turn_mock.assert_called_once_with(...) to
await-based assertion append_turn_mock.assert_awaited_once_with(...) and
likewise change get_topic_summary_mock.assert_called_once_with(...) to
get_topic_summary_mock.assert_awaited_once_with(...). Also remove timing-based
await asyncio.sleep(0.1) and replace with deterministic synchronization: await
the spawned background task or wait on an asyncio.Event/Task.result() that the
test triggers so the AsyncMocks are guaranteed to have been awaited before
asserting.

---

Outside diff comments:
In `@tests/unit/utils/test_streaming_sse.py`:
- Around line 268-278: The test for text media type currently only checks that
shield_violation_generator produced items; update the
test_shield_violation_generator_text to also assert that the generated content
contains the expected violation message ("Violation message"). Locate the async
test_shield_violation_generator_text and after collecting result from
shield_violation_generator(..., MEDIA_TYPE_TEXT) add a content assertion (e.g.,
join or inspect result items) to confirm the string "Violation message" appears,
mirroring the JSON test's thoroughness.