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fix: handle_sse_response causing dangling client's read_stream #1812

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fix: handle_sse_response causing dangling client's read_stream #1812

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86ef957
draft commit of solution to issue #1811
ivanbelenky Dec 21, 2025
4419464
pragma no cover and standard error message
ivanbelenky Dec 21, 2025
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21 changes: 20 additions & 1 deletion src/mcp/client/streamable_http.py
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Original file line number Diff line number Diff line change
Expand Up @@ -428,11 +428,30 @@ async def _handle_sse_response(
return # Normal completion, no reconnect needed
except Exception as e: # pragma: no cover
logger.debug(f"SSE stream ended: {e}")
sse_error = e
else: # pragma: no cover
sse_error = None

# Stream ended without response - reconnect if we received an event with ID
if last_event_id is not None: # pragma: no branch
if last_event_id is not None:
logger.info("SSE stream disconnected, reconnecting...")
await self._handle_reconnection(ctx, last_event_id, retry_interval_ms)
else: # pragma: no cover
error_msg = "SSE stream disconnected without response"
if sse_error is not None:
error_msg = f"{error_msg}: {type(sse_error).__name__}: {sse_error}"
error_response = JSONRPCError(
jsonrpc="2.0",
id=ctx.session_message.message.root.id
if isinstance(ctx.session_message.message.root, JSONRPCRequest)
else "Unknown",
error=ErrorData(
code=-32000,
message=error_msg,
),
)
error_message = JSONRPCMessage(root=error_response)
await ctx.read_stream_writer.send(SessionMessage(error_message))

async def _handle_reconnection(
self,
Expand Down