[BUG] MCP server fails with FastMCP 2.8.1 - unexpected keyword argument 'log_level'

Description

The MCP server fails to start with FastMCP 2.8.1 due to passing 'log_level' parameter that is not supported.

Error

TypeError: FastMCP.run_stdio_async() got an unexpected keyword argument 'log_level'

Environment

Basic Memory: 0.13.8.dev1
FastMCP: 2.8.1
Python: 3.13.5
Installation method: uv tool

Root Cause

Commit 7be001c added 'log_level' parameter to fix deprecation warnings, but this is incompatible with FastMCP 2.8.1.

Workaround

None currently available in dev version.

Oops, my Claude code made this on its own, so sorry. Still debugging.

This is likely fixed in #150 and will be available in the next release.

I don't think it's the same.
I built the server from the main repo, but when I try to run it with the stdio transport, it throws:

2025-06-25 16:50:44.815 | /usr/local/lib/python3.12/site-packages/sqlalchemy/sql/schema.py:3624: DeprecationWarning: datetime.datetime.utcnow() is deprecated and scheduled for removal in a future version. Use timezone-aware objects to represent datetimes in UTC: datetime.datetime.now(datetime.UTC).
2025-06-25 16:50:44.815 |   return util.wrap_callable(lambda ctx: fn(), fn)  # type: ignore
2025-06-25 16:50:45.110 | ╭───────────────────── Traceback (most recent call last) ──────────────────────╮
2025-06-25 16:50:45.110 | │ /usr/local/lib/python3.12/site-packages/basic_memory/cli/commands/mcp.py:79  │
2025-06-25 16:50:45.110 | │ in mcp                                                                       │
2025-06-25 16:50:45.110 | │                                                                              │
2025-06-25 16:50:45.110 | │   76 │   logger.info(f"Starting MCP server with {transport.upper()} transpor │
2025-06-25 16:50:45.110 | │   77 │                                                                       │
2025-06-25 16:50:45.110 | │   78 │   if transport == "stdio":                                            │
2025-06-25 16:50:45.110 | │ ❱ 79 │   │   mcp_server.run(                                                 │
2025-06-25 16:50:45.110 | │   80 │   │   │   transport=transport,                                        │
2025-06-25 16:50:45.110 | │   81 │   │   │   log_level="INFO",                                           │
2025-06-25 16:50:45.110 | │   82 │   │   )                                                               │
2025-06-25 16:50:45.110 | │                                                                              │
2025-06-25 16:50:45.110 | │ ╭───────────────────────────────── locals ─────────────────────────────────╮ │
2025-06-25 16:50:45.110 | │ │   app_config = BasicMemoryConfig(                                        │ │
2025-06-25 16:50:45.110 | │ │                │   env='dev',                                            │ │
2025-06-25 16:50:45.110 | │ │                │   projects={'main': '/root/basic-memory'},              │ │
2025-06-25 16:50:45.110 | │ │                │   default_project='main',                               │ │
2025-06-25 16:50:45.110 | │ │                │   log_level='INFO',                                     │ │
2025-06-25 16:50:45.110 | │ │                │   sync_delay=1000,                                      │ │
2025-06-25 16:50:45.110 | │ │                │   update_permalinks_on_move=False,                      │ │
2025-06-25 16:50:45.110 | │ │                │   sync_changes=True                                     │ │
2025-06-25 16:50:45.110 | │ │                )                                                         │ │
2025-06-25 16:50:45.110 | │ │ auth_enabled = False                                                     │ │
2025-06-25 16:50:45.110 | │ │         host = '0.0.0.0'                                                 │ │
2025-06-25 16:50:45.110 | │ │           os = <module 'os' (frozen)>                                    │ │
2025-06-25 16:50:45.110 | │ │         path = '/mcp'                                                    │ │
2025-06-25 16:50:45.110 | │ │         port = 8000                                                      │ │
2025-06-25 16:50:45.110 | │ │  sync_thread = <Thread(Thread-2 (run_file_sync), started daemon          │ │
2025-06-25 16:50:45.110 | │ │                281473540223360)>                                         │ │
2025-06-25 16:50:45.110 | │ │    threading = <module 'threading' from                                  │ │
2025-06-25 16:50:45.110 | │ │                '/usr/local/lib/python3.12/threading.py'>                 │ │
2025-06-25 16:50:45.110 | │ │    transport = 'stdio'                                                   │ │
2025-06-25 16:50:45.110 | │ ╰──────────────────────────────────────────────────────────────────────────╯ │
2025-06-25 16:50:45.110 | │                                                                              │
2025-06-25 16:50:45.110 | │ /usr/local/lib/python3.12/site-packages/fastmcp/server/server.py:315 in run  │
2025-06-25 16:50:45.110 | │                                                                              │
2025-06-25 16:50:45.110 | │    312 │   │   │   transport: Transport protocol to use ("stdio", "sse", or  │
2025-06-25 16:50:45.110 | │    313 │   │   """                                                           │
2025-06-25 16:50:45.110 | │    314 │   │                                                                 │
2025-06-25 16:50:45.110 | │ ❱  315 │   │   anyio.run(partial(self.run_async, transport, **transport_kwar │
2025-06-25 16:50:45.110 | │    316 │                                                                     │
2025-06-25 16:50:45.110 | │    317 │   def _setup_handlers(self) -> None:                                │
2025-06-25 16:50:45.110 | │    318 │   │   """Set up core MCP protocol handlers."""                      │
2025-06-25 16:50:45.110 | │                                                                              │
2025-06-25 16:50:45.110 | │ ╭────────────────── locals ──────────────────╮                               │
2025-06-25 16:50:45.110 | │ │             self = FastMCP('Basic Memory') │                               │
2025-06-25 16:50:45.110 | │ │        transport = 'stdio'                 │                               │
2025-06-25 16:50:45.110 | │ │ transport_kwargs = {'log_level': 'INFO'}   │                               │
2025-06-25 16:50:45.110 | │ ╰────────────────────────────────────────────╯                               │
2025-06-25 16:50:45.110 | │                                                                              │
2025-06-25 16:50:45.110 | │ /usr/local/lib/python3.12/site-packages/anyio/_core/_eventloop.py:74 in run  │
2025-06-25 16:50:45.110 | │                                                                              │
2025-06-25 16:50:45.110 | │    71 │                                                                      │
2025-06-25 16:50:45.110 | │    72 │   try:                                                               │
2025-06-25 16:50:45.110 | │    73 │   │   backend_options = backend_options or {}                        │
2025-06-25 16:50:45.110 | │ ❱  74 │   │   return async_backend.run(func, args, {}, backend_options)      │
2025-06-25 16:50:45.110 | │    75 │   finally:                                                           │
2025-06-25 16:50:45.110 | │    76 │   │   if token:                                                      │
2025-06-25 16:50:45.110 | │    77 │   │   │   sniffio.current_async_library_cvar.reset(token)            │
2025-06-25 16:50:45.110 | │                                                                              │
2025-06-25 16:50:45.110 | │ ╭───────────────────────────────── locals ─────────────────────────────────╮ │
2025-06-25 16:50:45.110 | │ │            args = ()                                                     │ │
2025-06-25 16:50:45.110 | │ │         backend = 'asyncio'                                              │ │
2025-06-25 16:50:45.110 | │ │ backend_options = {}                                                     │ │
2025-06-25 16:50:45.110 | │ │            func = functools.partial(<bound method FastMCP.run_async of   │ │
2025-06-25 16:50:45.110 | │ │                   FastMCP('Basic Memory')>, 'stdio', log_level='INFO')   │ │
2025-06-25 16:50:45.110 | │ │           token = <Token used var=<ContextVar                            │ │
2025-06-25 16:50:45.110 | │ │                   name='current_async_library_cvar' default=None at      │ │
2025-06-25 16:50:45.110 | │ │                   0xffffb3c9a250> at 0xffffabcd1bc0>                     │ │
2025-06-25 16:50:45.110 | │ ╰──────────────────────────────────────────────────────────────────────────╯ │
2025-06-25 16:50:45.110 | │                                                                              │
2025-06-25 16:50:45.110 | │ /usr/local/lib/python3.12/site-packages/anyio/_backends/_asyncio.py:2310 in  │
2025-06-25 16:50:45.110 | │ run                                                                          │
2025-06-25 16:50:45.110 | │                                                                              │
2025-06-25 16:50:45.110 | │   2307 │   │   │   loop_factory = uvloop.new_event_loop                      │
2025-06-25 16:50:45.110 | │   2308 │   │                                                                 │
2025-06-25 16:50:45.110 | │   2309 │   │   with Runner(debug=debug, loop_factory=loop_factory) as runner │
2025-06-25 16:50:45.110 | │ ❱ 2310 │   │   │   return runner.run(wrapper())                              │
2025-06-25 16:50:45.110 | │   2311 │                                                                     │
2025-06-25 16:50:45.110 | │   2312 │   @classmethod                                                      │
2025-06-25 16:50:45.110 | │   2313 │   def current_token(cls) -> object:                                 │
2025-06-25 16:50:45.110 | │                                                                              │
2025-06-25 16:50:45.110 | │ ╭───────────────────────────────── locals ─────────────────────────────────╮ │
2025-06-25 16:50:45.110 | │ │         args = ()                                                        │ │
2025-06-25 16:50:45.110 | │ │        debug = None                                                      │ │
2025-06-25 16:50:45.110 | │ │         func = functools.partial(<bound method FastMCP.run_async of      │ │
2025-06-25 16:50:45.110 | │ │                FastMCP('Basic Memory')>, 'stdio', log_level='INFO')      │ │
2025-06-25 16:50:45.110 | │ │       kwargs = {}                                                        │ │
2025-06-25 16:50:45.110 | │ │ loop_factory = None                                                      │ │
2025-06-25 16:50:45.110 | │ │      options = {}                                                        │ │
2025-06-25 16:50:45.110 | │ │       runner = <asyncio.runners.Runner object at 0xffffabdb8aa0>         │ │
2025-06-25 16:50:45.110 | │ ╰──────────────────────────────────────────────────────────────────────────╯ │
2025-06-25 16:50:45.110 | │                                                                              │
2025-06-25 16:50:45.110 | │ /usr/local/lib/python3.12/asyncio/runners.py:118 in run                      │
2025-06-25 16:50:45.110 | │                                                                              │
2025-06-25 16:50:45.110 | │   115 │   │                                                                  │
2025-06-25 16:50:45.110 | │   116 │   │   self._interrupt_count = 0                                      │
2025-06-25 16:50:45.110 | │   117 │   │   try:                                                           │
2025-06-25 16:50:45.110 | │ ❱ 118 │   │   │   return self._loop.run_until_complete(task)                 │
2025-06-25 16:50:45.110 | │   119 │   │   except exceptions.CancelledError:                              │
2025-06-25 16:50:45.110 | │   120 │   │   │   if self._interrupt_count > 0:                              │
2025-06-25 16:50:45.110 | │   121 │   │   │   │   uncancel = getattr(task, "uncancel", None)             │
2025-06-25 16:50:45.110 | │                                                                              │
2025-06-25 16:50:45.110 | │ ╭───────────────────────────────── locals ─────────────────────────────────╮ │
2025-06-25 16:50:45.110 | │ │        context = <_contextvars.Context object at 0xffffabe74ec0>         │ │
2025-06-25 16:50:45.110 | │ │           coro = <coroutine object AsyncIOBackend.run.<locals>.wrapper   │ │
2025-06-25 16:50:45.110 | │ │                  at 0xffffaba21a80>                                      │ │
2025-06-25 16:50:45.110 | │ │           self = <asyncio.runners.Runner object at 0xffffabdb8aa0>       │ │
2025-06-25 16:50:45.110 | │ │ sigint_handler = functools.partial(<bound method Runner._on_sigint of    │ │
2025-06-25 16:50:45.110 | │ │                  <asyncio.runners.Runner object at 0xffffabdb8aa0>>,     │ │
2025-06-25 16:50:45.110 | │ │                  main_task=<Task finished name='functools'               │ │
2025-06-25 16:50:45.110 | │ │                  coro=<AsyncIOBackend.run.<locals>.wrapper() done,       │ │
2025-06-25 16:50:45.110 | │ │                  defined at                                              │ │
2025-06-25 16:50:45.110 | │ │                  /usr/local/lib/python3.12/site-packages/anyio/_backend… │ │
2025-06-25 16:50:45.110 | │ │                  exception=TypeError("FastMCP.run_stdio_async() got an   │ │
2025-06-25 16:50:45.110 | │ │                  unexpected keyword argument 'log_level'")>)             │ │
2025-06-25 16:50:45.110 | │ │           task = <Task finished name='functools'                         │ │
2025-06-25 16:50:45.110 | │ │                  coro=<AsyncIOBackend.run.<locals>.wrapper() done,       │ │
2025-06-25 16:50:45.110 | │ │                  defined at                                              │ │
2025-06-25 16:50:45.110 | │ │                  /usr/local/lib/python3.12/site-packages/anyio/_backend… │ │
2025-06-25 16:50:45.110 | │ │                  exception=TypeError("FastMCP.run_stdio_async() got an   │ │
2025-06-25 16:50:45.110 | │ │                  unexpected keyword argument 'log_level'")>              │ │
2025-06-25 16:50:45.110 | │ ╰──────────────────────────────────────────────────────────────────────────╯ │
2025-06-25 16:50:45.110 | │                                                                              │
2025-06-25 16:50:45.110 | │ /usr/local/lib/python3.12/asyncio/base_events.py:691 in run_until_complete   │
2025-06-25 16:50:45.110 | │                                                                              │
2025-06-25 16:50:45.110 | │    688 │   │   if not future.done():                                         │
2025-06-25 16:50:45.110 | │    689 │   │   │   raise RuntimeError('Event loop stopped before Future comp │
2025-06-25 16:50:45.110 | │    690 │   │                                                                 │
2025-06-25 16:50:45.110 | │ ❱  691 │   │   return future.result()                                        │
2025-06-25 16:50:45.110 | │    692 │                                                                     │
2025-06-25 16:50:45.110 | │    693 │   def stop(self):                                                   │
2025-06-25 16:50:45.110 | │    694 │   │   """Stop running the event loop.                               │
2025-06-25 16:50:45.110 | │                                                                              │
2025-06-25 16:50:45.110 | │ ╭───────────────────────────────── locals ─────────────────────────────────╮ │
2025-06-25 16:50:45.110 | │ │   future = <Task finished name='functools'                               │ │
2025-06-25 16:50:45.110 | │ │            coro=<AsyncIOBackend.run.<locals>.wrapper() done, defined at  │ │
2025-06-25 16:50:45.110 | │ │            /usr/local/lib/python3.12/site-packages/anyio/_backends/_asy… │ │
2025-06-25 16:50:45.110 | │ │            exception=TypeError("FastMCP.run_stdio_async() got an         │ │
2025-06-25 16:50:45.110 | │ │            unexpected keyword argument 'log_level'")>                    │ │
2025-06-25 16:50:45.110 | │ │ new_task = False                                                         │ │
2025-06-25 16:50:45.110 | │ │     self = <_UnixSelectorEventLoop running=False closed=True             │ │
2025-06-25 16:50:45.110 | │ │            debug=False>                                                  │ │
2025-06-25 16:50:45.110 | │ ╰──────────────────────────────────────────────────────────────────────────╯ │
2025-06-25 16:50:45.110 | │                                                                              │
2025-06-25 16:50:45.110 | │ /usr/local/lib/python3.12/site-packages/anyio/_backends/_asyncio.py:2298 in  │
2025-06-25 16:50:45.110 | │ wrapper                                                                      │
2025-06-25 16:50:45.110 | │                                                                              │
2025-06-25 16:50:45.110 | │   2295 │   │   │   _task_states[task] = TaskState(None, None)                │
2025-06-25 16:50:45.110 | │   2296 │   │   │                                                             │
2025-06-25 16:50:45.110 | │   2297 │   │   │   try:                                                      │
2025-06-25 16:50:45.110 | │ ❱ 2298 │   │   │   │   return await func(*args)                              │
2025-06-25 16:50:45.110 | │   2299 │   │   │   finally:                                                  │
2025-06-25 16:50:45.110 | │   2300 │   │   │   │   del _task_states[task]                                │
2025-06-25 16:50:45.110 | │   2301                                                                       │
2025-06-25 16:50:45.110 | │                                                                              │
2025-06-25 16:50:45.110 | │ ╭───────────────────────────────── locals ─────────────────────────────────╮ │
2025-06-25 16:50:45.110 | │ │ args = ()                                                                │ │
2025-06-25 16:50:45.110 | │ │ func = functools.partial(<bound method FastMCP.run_async of              │ │
2025-06-25 16:50:45.110 | │ │        FastMCP('Basic Memory')>, 'stdio', log_level='INFO')              │ │
2025-06-25 16:50:45.110 | │ │ task = <Task finished name='functools'                                   │ │
2025-06-25 16:50:45.110 | │ │        coro=<AsyncIOBackend.run.<locals>.wrapper() done, defined at      │ │
2025-06-25 16:50:45.110 | │ │        /usr/local/lib/python3.12/site-packages/anyio/_backends/_asyncio… │ │
2025-06-25 16:50:45.110 | │ │        exception=TypeError("FastMCP.run_stdio_async() got an unexpected  │ │
2025-06-25 16:50:45.110 | │ │        keyword argument 'log_level'")>                                   │ │
2025-06-25 16:50:45.110 | │ ╰──────────────────────────────────────────────────────────────────────────╯ │
2025-06-25 16:50:45.110 | │                                                                              │
2025-06-25 16:50:45.110 | │ /usr/local/lib/python3.12/site-packages/fastmcp/server/server.py:298 in      │
2025-06-25 16:50:45.110 | │ run_async                                                                    │
2025-06-25 16:50:45.110 | │                                                                              │
2025-06-25 16:50:45.110 | │    295 │   │   │   raise ValueError(f"Unknown transport: {transport}")       │
2025-06-25 16:50:45.110 | │    296 │   │                                                                 │
2025-06-25 16:50:45.110 | │    297 │   │   if transport == "stdio":                                      │
2025-06-25 16:50:45.110 | │ ❱  298 │   │   │   await self.run_stdio_async(**transport_kwargs)            │
2025-06-25 16:50:45.110 | │    299 │   │   elif transport in {"http", "sse", "streamable-http"}:         │
2025-06-25 16:50:45.110 | │    300 │   │   │   await self.run_http_async(transport=transport, **transpor │
2025-06-25 16:50:45.110 | │    301 │   │   else:                                                         │
2025-06-25 16:50:45.110 | │                                                                              │
2025-06-25 16:50:45.110 | │ ╭────────────────── locals ──────────────────╮                               │
2025-06-25 16:50:45.110 | │ │             self = FastMCP('Basic Memory') │                               │
2025-06-25 16:50:45.110 | │ │        transport = 'stdio'                 │                               │
2025-06-25 16:50:45.110 | │ │ transport_kwargs = {'log_level': 'INFO'}   │                               │
2025-06-25 16:50:45.110 | │ ╰────────────────────────────────────────────╯                               │
2025-06-25 16:50:45.110 | ╰──────────────────────────────────────────────────────────────────────────────╯
2025-06-25 16:50:45.110 | TypeError: FastMCP.run_stdio_async() got an unexpected keyword argument 
2025-06-25 16:50:45.110 | 'log_level'

@claude

@claude can you look at the user the error is reporting an come up with a suggestion?

@phernandez

Claude finished @phernandez's task —— View job

Analyzing MCP Server Compatibility Issue

I've analyzed the FastMCP 2.8.1 compatibility issue and identified the root cause and solution.

Todo List:

Read current MCP server implementation
Analyze FastMCP version compatibility
Propose backward-compatible solution
Provide specific code recommendations

Root Cause Analysis

The issue occurs in src/basic_memory/cli/commands/mcp.py at lines 79 and 89 where mcp_server.run() is called with log_level="INFO":

mcp_server.run(
    transport=transport,
    log_level="INFO",  # This parameter is not supported in FastMCP 2.8.1
)

The Problem:

The log_level parameter was added to fix deprecation warnings (as mentioned in commit 7be001c)
FastMCP 2.8.1 doesn't support the log_level parameter in its run_stdio_async() method
This causes: TypeError: FastMCP.run_stdio_async() got an unexpected keyword argument 'log_level'
Simply removing log_level causes the server to loop infinitely because the underlying issue isn't addressed

Current Constraint:

The project requires fastmcp>=2.3.4 in pyproject.toml (line 33)
User is running FastMCP 2.8.1 which has API changes from earlier versions

Proposed Solution

I recommend implementing a version-aware parameter handling approach. Here are the options:

Option 1: Version Detection (Recommended)

import inspect
from fastmcp import FastMCP

def get_supported_run_params(transport: str) -> dict:
    """Get supported parameters for FastMCP.run() based on version/API."""
    if transport == "stdio":
        # Check if run_stdio_async supports log_level
        run_method = getattr(mcp_server, 'run_stdio_async', None)
        if run_method and 'log_level' in inspect.signature(run_method).parameters:
            return {"log_level": "INFO"}
    elif transport in ["streamable-http", "sse"]:
        # Check if run_http_async supports log_level  
        run_method = getattr(mcp_server, 'run_http_async', None)
        if run_method and 'log_level' in inspect.signature(run_method).parameters:
            return {"log_level": "INFO"}
    
    return {}

# Usage:
extra_params = get_supported_run_params(transport)
if transport == "stdio":
    mcp_server.run(transport=transport, **extra_params)
elif transport in ["streamable-http", "sse"]:
    mcp_server.run(transport=transport, host=host, port=port, path=path, **extra_params)

Option 2: Try/Except Approach (Simpler)

def run_mcp_server_safely(transport: str, **kwargs):
    """Run MCP server with graceful parameter handling."""
    try:
        mcp_server.run(transport=transport, log_level="INFO", **kwargs)
    except TypeError as e:
        if "unexpected keyword argument 'log_level'" in str(e):
            # Fallback: run without log_level parameter
            logger.warning("FastMCP version doesn't support log_level parameter, running without it")
            mcp_server.run(transport=transport, **kwargs)
        else:
            raise

Option 3: Pin FastMCP Version (Conservative)

Update pyproject.toml to pin to a specific version range that supports log_level:

"fastmcp>=2.3.4,<2.8.0",  # Exclude versions that don't support log_level

Recommendation

I recommend Option 1 (Version Detection) because:

It's future-proof and works with any FastMCP version
It maintains the logging functionality when available
It doesn't restrict the FastMCP version unnecessarily
It follows Python best practices for API compatibility

Would you like me to implement this solution?

I'm fixing this right now.

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[BUG] MCP server fails with FastMCP 2.8.1 - unexpected keyword argument 'log_level' #164

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Root Cause

Workaround

Analyzing MCP Server Compatibility Issue

Root Cause Analysis

Proposed Solution

Option 1: Version Detection (Recommended)

Option 2: Try/Except Approach (Simpler)

Option 3: Pin FastMCP Version (Conservative)

Recommendation

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[BUG] MCP server fails with FastMCP 2.8.1 - unexpected keyword argument 'log_level' #164

Description

Description

Error

Environment

Root Cause

Workaround

Activity

potatopotaro commented on Jun 21, 2025

groksrc commented on Jun 23, 2025

adamdrzewiecki commented on Jun 25, 2025

phernandez commented on Jun 25, 2025

claude commented on Jun 25, 2025

Analyzing MCP Server Compatibility Issue

Root Cause Analysis

Proposed Solution

Option 1: Version Detection (Recommended)

Option 2: Try/Except Approach (Simpler)

Option 3: Pin FastMCP Version (Conservative)

Recommendation

phernandez commented on Jun 26, 2025

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