SurfSense/surfsense_backend/app/tasks/chat
CREDO23 c3db25302b perf(chat): kill auto-pin preflight + speculative build, rely on reactive 429 recovery
The preflight pattern probed the LLM with a 1-token ping before each
cold turn (when requested_llm_config_id==0, llm_config_id<0, and the
45s healthy TTL had expired) to detect 429s before fanning out into
planner/classifier/title-gen. To absorb its ~1-5s RTT cost we built the
agent speculatively in parallel; on 429 we discarded the build and
repinned.

Three problems with that design:

1. False security. Provider rate limits are token-bucket. A 1-token
   ping consumes ~5 tokens; the real request consumes 10-50K. The
   probe can return 200 while the real call still 429s.
2. Pure overhead in the common case. On warm-agent-cache turns the
   probe dominates wall time: ~2.5s of TTFT pure tax for ~99% of users
   who never see a 429.
3. The in-stream recovery loop (catch of _is_provider_rate_limited
   gated by not _first_event_logged) already does the right thing
   reactively: mark_runtime_cooldown -> resolve_or_get_pinned_llm_config_id
   with exclude_config_ids={previous} -> rebuild agent -> retry the
   stream. Preflight was never the only safety net; it was a redundant
   probe in front of one.

Changes:
- Delete _preflight_llm, _settle_speculative_agent_build, and the
  _PREFLIGHT_TIMEOUT_SEC / _PREFLIGHT_MAX_TOKENS constants.
- Drop the parallel agent_build_task / preflight_task plumbing in
  both stream_new_chat and stream_resume_chat; build the agent inline
  with await _build_main_agent_for_thread(...).
- Drop the unused is_recently_healthy / mark_healthy imports here
  (still exported from auto_model_pin_service since OpenRouter
  catalogue refresh and a few tests reference clear_healthy).
- Remove the obsolete preflight + settle-speculative tests from
  test_stream_new_chat_contract.py.

Net: -447 LOC. ~2.5s removed from TTFT on every cold preflight-eligible
turn. 429 recovery path is unchanged - same repin/rebuild/retry, just
not paid in advance on the healthy path.
2026-05-20 11:03:08 +02:00
..
streaming chat/stream_new_chat: emit one SSE frame per pending interrupt 2026-05-13 20:59:48 +02:00
content_builder.py feat: improved document, folder mentions rendering 2026-05-09 22:15:51 -07:00
persistence.py feat: improved document, folder mentions rendering 2026-05-09 22:15:51 -07:00
stream_new_chat.py perf(chat): kill auto-pin preflight + speculative build, rely on reactive 429 recovery 2026-05-20 11:03:08 +02:00