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fix: gracefully terminate active Streamable HTTP sessions during shutdown (#2150) #2746

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fix: gracefully terminate active Streamable HTTP sessions during shutdown (#2150) #2746

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686d483
fix: gracefully terminate active StreamableHTTP sessions during shutdown
kaushik701 Jun 1, 2026
e37d8aa
fix: close SSE stream writers in terminate() to allow graceful comple…
kaushik701 Jun 1, 2026
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5 changes: 5 additions & 0 deletions src/mcp/server/streamable_http.py
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Original file line number Diff line number Diff line change
Expand Up @@ -771,6 +771,11 @@ async def terminate(self) -> None:
self._terminated = True
logger.info(f"Terminating session: {self.mcp_session_id}")

# Close all SSE stream writers to allow EventSourceResponse to complete gracefully
for writer in list(self._sse_stream_writers.values()):
writer.close()
self._sse_stream_writers.clear()

# We need a copy of the keys to avoid modification during iteration
request_stream_keys = list(self._request_streams.keys())

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6 changes: 6 additions & 0 deletions src/mcp/server/streamable_http_manager.py
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Expand Up @@ -133,6 +133,12 @@ async def lifespan(app: Starlette) -> AsyncIterator[None]:
yield # Let the application run
finally:
logger.info("StreamableHTTP session manager shutting down")
# Gracefully terminate all active sessions before cancelling tasks
for transport in list(self._server_instances.values()):
try:
await transport.terminate()
except Exception:
logger.debug("Error terminating transport during shutdown", exc_info=True)
# Cancel task group to stop all spawned tasks
tg.cancel_scope.cancel()
self._task_group = None
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