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fix(server): add timeout to MCP connection initialization #2922

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fix(server): add timeout to MCP connection initialization #2922

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15 changes: 14 additions & 1 deletion backend/chainlit/server.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1482,7 +1482,20 @@ async def _mcp_session_runner() -> None:
)

# Wait for the background task to finish initialisation.
await ready_event.wait()
try:
await asyncio.wait_for(ready_event.wait(), timeout=30)
except asyncio.TimeoutError:
task.cancel()
try:
await task
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@cubic-dev-ai cubic-dev-ai Bot May 10, 2026

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P1: The timeout path can still hang because it awaits the cancelled MCP task without any second timeout.

Prompt for AI agents 
Check if this issue is valid — if so, understand the root cause and fix it. At backend/chainlit/server.py, line 1490:

<comment>The timeout path can still hang because it awaits the cancelled MCP task without any second timeout.</comment>

<file context>
@@ -1482,7 +1482,20 @@ async def _mcp_session_runner() -> None:
+    except asyncio.TimeoutError:
+        task.cancel()
+        try:
+            await task
+        except BaseException:
+            pass
</file context>

except BaseException:
pass
return JSONResponse(
status_code=504,
content={
"detail": f"MCP connection to '{payload.name}' timed out during initialization"
},
)

if "error" in result_holder:
# The task already exited and cleaned up its exit stack.
Expand Down