Replace the earlier frontend-reset approach with a backend side-channel
approach that preserves the queue (event, data) tuple shape.
Problem (Opus catch):
- Live SSE frames emitted by _sse() in api/streaming.py:2296 carried no
'id:' field. Only journal-replay frames (via _sse_with_id) emitted IDs.
- Frontend's _lastRunJournalSeq cursor stayed at 0 during live streaming.
- Mid-stream error → reconnect-to-replay arrived with after_seq=0.
- Server replayed every journaled event from seq 1.
- assistantText (closure-scoped) had accumulated all live tokens already
→ double-rendered output.
Fix:
- api/config.py: STREAM_LAST_EVENT_ID: dict = {} module-level dict.
- api/streaming.py put(): capture journal event_id, write to
STREAM_LAST_EVENT_ID[stream_id]. Keep queue tuple as (event, data).
- api/routes.py _handle_sse_stream: read STREAM_LAST_EVENT_ID[stream_id]
at emit time, use _sse_with_id when set.
- api/streaming.py finally block: pop STREAM_LAST_EVENT_ID for cleanup.
Why side-channel instead of 3-tuple:
- Earlier attempt (queue tuple → (event, data, event_id)) broke 4 existing
tests: test_cancel_interrupt, test_sprint42, test_sprint51,
test_issue1857_usage_overwrite. These all unpack 'event, data = q.get()'.
- Frontend-reset approach (reset assistantText before replay) broke 3
other tests: test_smooth_text_fade, test_streaming_markdown,
test_streaming_race_fix. _wireSSE must NOT reset accumulators because
legacy reconnect doesn't replay events; only journal-replay does.
Side-channel preserves both invariants:
- Queue contract stays (event, data) — legacy consumers unbroken.
- Frontend accumulators stay alive on _wireSSE — legacy reconnect unbroken.
- Live SSE emits 'id:' so the journal cursor advances correctly.
6 regression tests added in test_stage364_opus_live_sse_event_id.py.
1 existing test (test_run_journal_streaming_static.test_streaming_journals_sse_events_before_queue_delivery) updated to be tuple-shape-agnostic.
Test results:
- Full pytest: 5713 passed, 10 skipped, 1 xfailed, 2 xpassed, 0 failed
- Previously-failing 5 tests: ALL PASS
- 6 new regression tests: ALL PASS
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