modelcontextprotocol / modelcontextprotocol/python-sdk
`simple-auth` is not working as expected
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Description
Initial Checks
- I confirm that I'm using the latest version of MCP Python SDK
- I confirm that I searched for my issue in https://github.com/modelcontextprotocol/python-sdk/issues before opening this issue
Description
I am trying to follow the example as described in examples/servers/simple-auth. However, when running the mcp-simple-auth-client I am getting the following error (and I know how to fix it):
$ MCP_SERVER_PORT=8000 MCP_TRANSPORT_TYPE=streamable-http uv run mcp-simple-auth-client
🚀 Simple MCP Auth Client
Connecting to: http://localhost:8000/mcp
Transport type: streamable-http
🔗 Attempting to connect to http://localhost:8000/mcp...
🖥️ Started callback server on http://localhost:3030
📡 Opening StreamableHTTP transport connection with auth...
🤝 Initializing MCP session...
⚡ Starting session initialization...
❌ Failed to connect: unhandled errors in a TaskGroup (1 sub-exception)
+ Exception Group Traceback (most recent call last):
| File "/home/python-sdk/examples/clients/simple-auth-client/mcp_simple_auth_client/main.py", line 230, in connect
| async with streamable_http_client(url=self.server_url, http_client=custom_client) as (
| File "/usr/lib/python3.12/contextlib.py", line 231, in __aexit__
| await self.gen.athrow(value)
| File "/home/python-sdk/src/mcp/client/streamable_http.py", line 563, in streamable_http_client
| async with (
| File "/home/python-sdk/.venv/lib/python3.12/site-packages/anyio/_backends/_asyncio.py", line 772, in __aexit__
| raise BaseExceptionGroup(
| ExceptionGroup: unhandled errors in a TaskGroup (1 sub-exception)
+-+---------------- 1 ----------------
| Traceback (most recent call last):
| File "/home/python-sdk/.venv/lib/python3.12/site-packages/httpx/_transports/default.py", line 101, in map_httpcore_exceptions
| yield
| File "/home/python-sdk/.venv/lib/python3.12/site-packages/httpx/_transports/default.py", line 394, in handle_async_request
| resp = await self._pool.handle_async_request(req)
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
| File "/home/python-sdk/.venv/lib/python3.12/site-packages/httpcore/_async/connection_pool.py", line 256, in handle_async_request
| raise exc from None
| File "/home/python-sdk/.venv/lib/python3.12/site-packages/httpcore/_async/connection_pool.py", line 236, in handle_async_request
| response = await connection.handle_async_request(
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
| File "/home/python-sdk/.venv/lib/python3.12/site-packages/httpcore/_async/connection.py", line 101, in handle_async_request
| raise exc
| File "/home/python-sdk/.venv/lib/python3.12/site-packages/httpcore/_async/connection.py", line 78, in handle_async_request
| stream = await self._connect(request)
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
| File "/home/python-sdk/.venv/lib/python3.12/site-packages/httpcore/_async/connection.py", line 124, in _connect
| stream = await self._network_backend.connect_tcp(**kwargs)
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
| File "/home/python-sdk/.venv/lib/python3.12/site-packages/httpcore/_backends/auto.py", line 31, in connect_tcp
| return await self._backend.connect_tcp(
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
| File "/home/python-sdk/.venv/lib/python3.12/site-packages/httpcore/_backends/anyio.py", line 113, in connect_tcp
| with map_exceptions(exc_map):
| File "/usr/lib/python3.12/contextlib.py", line 158, in __exit__
| self.gen.throw(value)
| File "/home/python-sdk/.venv/lib/python3.12/site-packages/httpcore/_exceptions.py", line 14, in map_exceptions
| raise to_exc(exc) from exc
| httpcore.ConnectError: All connection attempts failed
|
| The above exception was the direct cause of the following exception:
|
| Traceback (most recent call last):
| File "/home/python-sdk/src/mcp/client/streamable_http.py", line 475, in handle_request_async
| await self._handle_post_request(ctx)
| File "/home/python-sdk/src/mcp/client/streamable_http.py", line 261, in _handle_post_request
| async with ctx.client.stream(
| File "/usr/lib/python3.12/contextlib.py", line 210, in __aenter__
| return await anext(self.gen)
| ^^^^^^^^^^^^^^^^^^^^^
| File "/home/python-sdk/.venv/lib/python3.12/site-packages/httpx/_client.py", line 1583, in stream
| response = await self.send(
| ^^^^^^^^^^^^^^^^
| File "/home/python-sdk/.venv/lib/python3.12/site-packages/httpx/_client.py", line 1629, in send
| response = await self._send_handling_auth(
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
| File "/home/python-sdk/.venv/lib/python3.12/site-packages/httpx/_client.py", line 1657, in _send_handling_auth
| response = await self._send_handling_redirects(
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
| File "/home/python-sdk/.venv/lib/python3.12/site-packages/httpx/_client.py", line 1694, in _send_handling_redirects
| response = await self._send_single_request(request)
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
| File "/home/python-sdk/.venv/lib/python3.12/site-packages/httpx/_client.py", line 1730, in _send_single_request
| response = await transport.handle_async_request(request)
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
| File "/home/python-sdk/.venv/lib/python3.12/site-packages/httpx/_transports/default.py", line 393, in handle_async_request
| with map_httpcore_exceptions():
| File "/usr/lib/python3.12/contextlib.py", line 158, in __exit__
| self.gen.throw(value)
| File "/home/python-sdk/.venv/lib/python3.12/site-packages/httpx/_transports/default.py", line 118, in map_httpcore_exceptions
| raise mapped_exc(message) from exc
| httpx.ConnectError: All connection attempts failed
+------------------------------------
I think the problem is that the server_url in the examples/servers/simple-auth/mcp_simple_auth/server.py includes the path (the /mcp part) whereas in the README it shows the base URL without the path should be used. Changing this locally fixed the problem for me.
I would also be willing to fix the TODO in examples/servers/simple-auth/mcp_simple_auth/simple_auth_provider.py if that's alright.
Example Code
terminal 1:
uv run mcp-simple-auth-as --port=9000
terminal 2:
uv run mcp-simple-auth-rs --port=8001 --auth-server=http://localhost:9000 --transport=streamable-http
terminal 3:
$ MCP_SERVER_PORT=8000 MCP_TRANSPORT_TYPE=streamable-http uv run mcp-simple-auth-client
🚀 Simple MCP Auth Client
Connecting to: http://localhost:8000/mcp
Transport type: streamable-http
🔗 Attempting to connect to http://localhost:8000/mcp...
🖥️ Started callback server on http://localhost:3030
📡 Opening StreamableHTTP transport connection with auth...
🤝 Initializing MCP session...
⚡ Starting session initialization...
❌ Failed to connect: unhandled errors in a TaskGroup (1 sub-exception)
+ Exception Group Traceback (most recent call last):
| File "/home/python-sdk/examples/clients/simple-auth-client/mcp_simple_auth_client/main.py", line 230, in connect
| async with streamable_http_client(url=self.server_url, http_client=custom_client) as (
| File "/usr/lib/python3.12/contextlib.py", line 231, in __aexit__
| await self.gen.athrow(value)
| File "/home/python-sdk/src/mcp/client/streamable_http.py", line 563, in streamable_http_client
| async with (
| File "/home/python-sdk/.venv/lib/python3.12/site-packages/anyio/_backends/_asyncio.py", line 772, in __aexit__
| raise BaseExceptionGroup(
| ExceptionGroup: unhandled errors in a TaskGroup (1 sub-exception)
+-+---------------- 1 ----------------
| Traceback (most recent call last):
| File "/home/python-sdk/.venv/lib/python3.12/site-packages/httpx/_transports/default.py", line 101, in map_httpcore_exceptions
| yield
| File "/home/python-sdk/.venv/lib/python3.12/site-packages/httpx/_transports/default.py", line 394, in handle_async_request
| resp = await self._pool.handle_async_request(req)
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
| File "/home/python-sdk/.venv/lib/python3.12/site-packages/httpcore/_async/connection_pool.py", line 256, in handle_async_request
| raise exc from None
| File "/home/python-sdk/.venv/lib/python3.12/site-packages/httpcore/_async/connection_pool.py", line 236, in handle_async_request
| response = await connection.handle_async_request(
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
| File "/home/python-sdk/.venv/lib/python3.12/site-packages/httpcore/_async/connection.py", line 101, in handle_async_request
| raise exc
| File "/home/python-sdk/.venv/lib/python3.12/site-packages/httpcore/_async/connection.py", line 78, in handle_async_request
| stream = await self._connect(request)
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
| File "/home/python-sdk/.venv/lib/python3.12/site-packages/httpcore/_async/connection.py", line 124, in _connect
| stream = await self._network_backend.connect_tcp(**kwargs)
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
| File "/home/python-sdk/.venv/lib/python3.12/site-packages/httpcore/_backends/auto.py", line 31, in connect_tcp
| return await self._backend.connect_tcp(
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
| File "/home/python-sdk/.venv/lib/python3.12/site-packages/httpcore/_backends/anyio.py", line 113, in connect_tcp
| with map_exceptions(exc_map):
| File "/usr/lib/python3.12/contextlib.py", line 158, in __exit__
| self.gen.throw(value)
| File "/home/python-sdk/.venv/lib/python3.12/site-packages/httpcore/_exceptions.py", line 14, in map_exceptions
| raise to_exc(exc) from exc
| httpcore.ConnectError: All connection attempts failed
|
| The above exception was the direct cause of the following exception:
|
| Traceback (most recent call last):
| File "/home/python-sdk/src/mcp/client/streamable_http.py", line 475, in handle_request_async
| await self._handle_post_request(ctx)
| File "/home/python-sdk/src/mcp/client/streamable_http.py", line 261, in _handle_post_request
| async with ctx.client.stream(
| File "/usr/lib/python3.12/contextlib.py", line 210, in __aenter__
| return await anext(self.gen)
| ^^^^^^^^^^^^^^^^^^^^^
| File "/home/python-sdk/.venv/lib/python3.12/site-packages/httpx/_client.py", line 1583, in stream
| response = await self.send(
| ^^^^^^^^^^^^^^^^
| File "/home/python-sdk/.venv/lib/python3.12/site-packages/httpx/_client.py", line 1629, in send
| response = await self._send_handling_auth(
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
| File "/home/python-sdk/.venv/lib/python3.12/site-packages/httpx/_client.py", line 1657, in _send_handling_auth
| response = await self._send_handling_redirects(
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
| File "/home/python-sdk/.venv/lib/python3.12/site-packages/httpx/_client.py", line 1694, in _send_handling_redirects
| response = await self._send_single_request(request)
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
| File "/home/python-sdk/.venv/lib/python3.12/site-packages/httpx/_client.py", line 1730, in _send_single_request
| response = await transport.handle_async_request(request)
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
| File "/home/python-sdk/.venv/lib/python3.12/site-packages/httpx/_transports/default.py", line 393, in handle_async_request
| with map_httpcore_exceptions():
| File "/usr/lib/python3.12/contextlib.py", line 158, in __exit__
| self.gen.throw(value)
| File "/home/python-sdk/.venv/lib/python3.12/site-packages/httpx/_transports/default.py", line 118, in map_httpcore_exceptions
| raise mapped_exc(message) from exc
| httpx.ConnectError: All connection attempts failed
+------------------------------------
Python & MCP Python SDK
`Python 3.12.3`
`mcp-simple-auth 0.1.0`
and MCP Python SDK:
$ git describe --tags
v1.25.0-180-g5d82649
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Compare examples/servers/simple-auth/mcp_simple_auth/server.py with the simple-auth README and reproduce the three-terminal commands using streamable-http. Check the server URL handling and verify that mcp-simple-auth-client connects successfully at the documented endpoint; the separate TODO is in simple_auth_provider.py around line 268.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- python
- Domain
- api, authentication
- Issue type
- Bug
- Difficulty
- 2/5
- Estimated time
- 1-3 hours
- Activity status
- Quiet
- Clarity
- Clearly specified
- Newbie friendliness
- 78/100