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Fix unhandled TaskGroup exceptions that occur in transport layer #999

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Fix unhandled TaskGroup exceptions that occur in transport layer #999

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18 changes: 13 additions & 5 deletions src/mcp/client/sse.py
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Original file line number Diff line number Diff line change
Expand Up @@ -51,8 +51,8 @@ async def sse_client(
read_stream_writer, read_stream = anyio.create_memory_object_stream(0)
write_stream, write_stream_reader = anyio.create_memory_object_stream(0)

async with anyio.create_task_group() as tg:
try:
try:
async with anyio.create_task_group() as tg:
logger.debug(f"Connecting to SSE endpoint: {remove_request_params(url)}")
async with httpx_client_factory(
headers=headers, auth=auth, timeout=httpx.Timeout(timeout, read=sse_read_timeout)
Expand Down Expand Up @@ -139,6 +139,14 @@ async def post_writer(endpoint_url: str):
yield read_stream, write_stream
finally:
tg.cancel_scope.cancel()
finally:
await read_stream_writer.aclose()
await write_stream.aclose()
except Exception as e:
logger.error(f"TaskGroup exception in SSE transport: {e}")
try:
await read_stream_writer.send(e)
except Exception:
logger.error(f"Failed to send TaskGroup exception to read stream: {e}")
raise

finally:
await read_stream_writer.aclose()
await write_stream.aclose()
17 changes: 12 additions & 5 deletions src/mcp/client/streamable_http.py
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Original file line number Diff line number Diff line change
Expand Up @@ -471,8 +471,8 @@ async def streamablehttp_client(
read_stream_writer, read_stream = anyio.create_memory_object_stream[SessionMessage | Exception](0)
write_stream, write_stream_reader = anyio.create_memory_object_stream[SessionMessage](0)

async with anyio.create_task_group() as tg:
try:
try:
async with anyio.create_task_group() as tg:
logger.debug(f"Connecting to StreamableHTTP endpoint: {url}")

async with httpx_client_factory(
Expand Down Expand Up @@ -504,6 +504,13 @@ def start_get_stream() -> None:
if transport.session_id and terminate_on_close:
await transport.terminate_session(client)
tg.cancel_scope.cancel()
finally:
await read_stream_writer.aclose()
await write_stream.aclose()
except Exception as e:
logger.error(f"TaskGroup exception in StreamableHTTP transport: {e}")
try:
await read_stream_writer.send(e)
except Exception:
logger.error(f"Failed to send TaskGroup exception to read stream: {e}")
raise
finally:
await read_stream_writer.aclose()
await write_stream.aclose()
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