Python: Emit SSE keepalive comments during idle AG-UI event streams#6965
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Python: Emit SSE keepalive comments during idle AG-UI event streams#6965kartikmadan11 wants to merge 2 commits into
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Pull request overview
This PR improves robustness of the Python AG-UI FastAPI SSE endpoint by emitting periodic SSE keepalive comments during idle gaps, preventing reverse proxies and EventSource clients from closing otherwise-healthy long-running streams (notably during “silent” reasoning/model phases). It adds a configurable keepalive_seconds parameter and validates the behavior with new endpoint tests.
Changes:
- Add
keepalive_seconds(default15) toadd_agent_framework_fastapi_endpointand emit: keepaliveSSE comments during idle gaps. - Refactor streaming to use a dedicated producer task feeding an
asyncio.Queue, so keepalive timeouts only affectqueue.get()rather than the protocol generator. - Add tests covering keepalive emission, disabled keepalive, and ensuring fast streams don’t interleave keepalives.
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.
| File | Description |
|---|---|
| python/packages/ag-ui/agent_framework_ag_ui/_endpoint.py | Adds configurable SSE keepalive support and introduces a producer/queue pattern to avoid canceling the underlying event generator on idle timeouts. |
| python/packages/ag-ui/tests/ag_ui/test_endpoint.py | Adds tests verifying keepalive behavior during idle gaps and ensuring disabling/fast-stream behavior works as intended. |
Reverse proxies and browser EventSource runtimes close connections that go silent for too long. Reasoning models can think for 30-60s without emitting events, triggering these timeouts. Adds a keepalive_seconds parameter (default 15) to add_agent_framework_fastapi_endpoint. The event iterator runs in a dedicated producer task feeding an asyncio.Queue so wait_for timeouts only cancel queue.get() rather than the generator itself, which would corrupt ContextVar state used by OTel hooks. Fixes microsoft#6941
reject negative keepalive_seconds early with ValueError bound event queue with maxsize=1 to preserve backpressure and avoid unbounded memory growth
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Thanks for your contribution, @kartikmadan11. I had this inflight and it's now published as #6980. |
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Reverse proxies and browser EventSource runtimes close connections that go silent for too long. Reasoning models can think for 30-60s without emitting events, triggering these timeouts.
Adds a
keepalive_secondsparameter (default 15) toadd_agent_framework_fastapi_endpoint. The event iterator runs in a dedicated producer task feeding anasyncio.Queuesowait_fortimeouts only cancelqueue.get()rather than the generator itself, which would corrupt ContextVar state used by OTel hooks.Fixes #6941