[Bug]: Not working with any streamableHttp MCP servers #67
Description
What happened?
I was doing a small agent when I run it I got this error. I tried it in different OS (Debian, Ubuntu), I tried more MCP servers that were working with other MCP host.
Version check
- Yes I was.
Relevant log output
# nerve run agent.yml
[08-29-25 16:23:36] INFO 🧠 nerve v1.8.0
[08-29-25 16:23:37] INFO 🧰 importing 14 tools from MCP server filesystem
Task exception was never retrieved
future: <Task finished name='Task-10' coro=<<async_generator_athrow without __name__>()> exception=SystemExit(0)>
Traceback (most recent call last):
File "/usr/lib/python3.11/asyncio/runners.py", line 190, in run
return runner.run(main)
^^^^^^^^^^^^^^^^
File "/usr/lib/python3.11/asyncio/runners.py", line 118, in run
return self._loop.run_until_complete(task)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/usr/lib/python3.11/asyncio/base_events.py", line 653, in run_until_complete
return future.result()
^^^^^^^^^^^^^^^
File "/usr/local/lib/python3.11/dist-packages/nerve/cli/run.py", line 83, in _run
actors=[await Agent.create_from_file(args.generator, args.input_path, args.conversation_strategy)],
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/usr/local/lib/python3.11/dist-packages/nerve/runtime/agent.py", line 102, in create_from_file
return await cls.create(
^^^^^^^^^^^^^^^^^
File "/usr/local/lib/python3.11/dist-packages/nerve/runtime/agent.py", line 74, in create
runtime = await Runtime.build(
^^^^^^^^^^^^^^^^^^^^
File "/usr/local/lib/python3.11/dist-packages/nerve/runtime/__init__.py", line 77, in build
server_tools = await mcp_compiler.get_tools_from_mcp(name, server, working_dir=working_dir)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/usr/local/lib/python3.11/dist-packages/nerve/tools/mcp/compiler.py", line 129, in get_tools_from_mcp
mpc_tools = await client.tools()
^^^^^^^^^^^^^^^^^^^^
File "/usr/local/lib/python3.11/dist-packages/nerve/tools/mcp/client.py", line 154, in tools
await self.connect()
File "/usr/local/lib/python3.11/dist-packages/nerve/tools/mcp/client.py", line 126, in connect
self._read_stream, self._write_stream = await self._exit_stack.enter_async_context(self._client_context)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
ValueError: too many values to unpack (expected 2)
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
File "/usr/local/lib/python3.11/dist-packages/nerve/tools/mcp/client.py", line 86, in _safe_stdio_context
async with stdio_client(server=self.server_params, errlog=sys.stderr) as (read_stream, write_stream):
File "/usr/lib/python3.11/contextlib.py", line 211, in __aexit__
await anext(self.gen)
RuntimeError: anext(): asynchronous generator is already running
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
File "/usr/local/lib/python3.11/dist-packages/typer/main.py", line 323, in __call__
return get_command(self)(*args, **kwargs)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/usr/local/lib/python3.11/dist-packages/click/core.py", line 1161, in __call__
return self.main(*args, **kwargs)
^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/usr/local/lib/python3.11/dist-packages/typer/core.py", line 740, in main
return _main(
^^^^^^
File "/usr/local/lib/python3.11/dist-packages/typer/core.py", line 195, in _main
rv = self.invoke(ctx)
^^^^^^^^^^^^^^^^
File "/usr/local/lib/python3.11/dist-packages/click/core.py", line 1697, in invoke
return _process_result(sub_ctx.command.invoke(sub_ctx))
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/usr/local/lib/python3.11/dist-packages/click/core.py", line 1443, in invoke
return ctx.invoke(self.callback, **ctx.params)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/usr/local/lib/python3.11/dist-packages/click/core.py", line 788, in invoke
return __callback(*args, **kwargs)
^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/usr/local/lib/python3.11/dist-packages/typer/main.py", line 698, in wrapper
return callback(**use_params)
^^^^^^^^^^^^^^^^^^^^^^
File "<string>", line 3, in func
File "/usr/local/lib/python3.11/dist-packages/nerve/cli/run.py", line 38, in run
asyncio.run(
File "/usr/lib/python3.11/asyncio/runners.py", line 189, in run
with Runner(debug=debug) as runner:
File "/usr/lib/python3.11/asyncio/runners.py", line 63, in __exit__
self.close()
File "/usr/lib/python3.11/asyncio/runners.py", line 72, in close
loop.run_until_complete(loop.shutdown_asyncgens())
File "/usr/lib/python3.11/asyncio/base_events.py", line 640, in run_until_complete
self.run_forever()
File "/usr/lib/python3.11/asyncio/base_events.py", line 607, in run_forever
self._run_once()
File "/usr/lib/python3.11/asyncio/base_events.py", line 1922, in _run_once
handle._run()
File "/usr/lib/python3.11/asyncio/events.py", line 80, in _run
self._context.run(self._callback, *self._args)
File "/usr/local/lib/python3.11/dist-packages/nerve/tools/mcp/client.py", line 98, in _safe_stdio_context
exit(0)
File "<frozen _sitebuiltins>", line 26, in __call__
SystemExit: 0
Exception ignored in: <async_generator object stdio_client at 0x7f21f6b22a40>
Traceback (most recent call last):
File "/usr/local/lib/python3.11/dist-packages/mcp/client/stdio/__init__.py", line 180, in stdio_client
async with (
File "/usr/local/lib/python3.11/dist-packages/anyio/_backends/_asyncio.py", line 736, in __aexit__
loop = get_running_loop()
^^^^^^^^^^^^^^^^^^
RuntimeError: no running event loopRelevant screenshots (optional)
agent.yml:
`root@debian:~/new-agent# cat agent.yml
agent: You are a helpful assistant!
task: Ask something...
using:
- task
- reasoning
mcp:
filesystem:
command: npx
args: ["-y", "@modelcontextprotocol/server-filesystem", "."]
github:
url: stream://fleet-mcp-github.ai.svc.cluster.local:8000/mcp`