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

[potatopotaro]

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.

[potatopotaro]

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

[groksrc]

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

[adamdrzewiecki]

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'

[phernandez]

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

[claude]

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:

1. The log_level parameter was added to fix deprecation warnings (as mentioned in commit 7be001c)
2. FastMCP 2.8.1 doesn't support the log_level parameter in its run_stdio_async() method
3. This causes: TypeError: FastMCP.run_stdio_async() got an unexpected keyword argument 'log_level'
4. 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?

---

[phernandez]

I'm fixing this right now.