PrefectHQ/fastmcp · error · AttributeError

module {__name__!r} has no attribute {name!r}

Error message

module {__name__!r} has no attribute {name!r}

What it means

This AttributeError is raised by the lazy module-level __getattr__ of fastmcp.apps when code accesses an attribute on the `fastmcp.apps` module that it does not know how to lazily import. The only lazily provided attribute is `FastMCPApp`; anything else falls through to this raise. It typically means a misspelled import or an attribute that lives in a submodule (e.g. fastmcp.apps.app) was referenced at module level.

Source

Thrown at fastmcp_slim/fastmcp/apps/__init__.py:42

    "AppConfig",
    "FastMCPApp",
    "PrefabAppConfig",
    "ResourceCSP",
    "ResourcePermissions",
    "app_config_to_meta_dict",
    "resolve_ui_mime_type",
]

if _TYPE_CHECKING:
    from fastmcp.apps.app import FastMCPApp as FastMCPApp


def __getattr__(name: str) -> object:
    if name == "FastMCPApp":
        from fastmcp.apps.app import FastMCPApp

        return FastMCPApp
    raise AttributeError(f"module {__name__!r} has no attribute {name!r}")

View on GitHub (pinned to 1f02114297)

Solutions

1. Use the exact exported name `FastMCPApp` (from fastmcp.apps import FastMCPApp) or import from the defining submodule, e.g. `from fastmcp.apps.app import ...`.
2. Check `dir(fastmcp.apps)` to see which attributes actually exist at module level.
3. Verify the installed fastmcp version supports the attribute (upgrade if it was added later).

Example fix

// before
from fastmcp.apps import AppFastMCP
// after
from fastmcp.apps import FastMCPApp

import fastmcp.apps
attr = "FastMCPApp"
if not hasattr(fastmcp.apps, attr):
    raise ImportError(f"fastmcp.apps has no attribute {attr!r}; use FastMCPApp or import from fastmcp.apps.app")

def has_apps_attr(name: str) -> bool:
    import fastmcp.apps
    return hasattr(fastmcp.apps, name)

try:
    from fastmcp.apps import FastMCPApp
except AttributeError as e:
    from fastmcp.apps.app import FastMCPApp  # or fix the name

When it happens

Trigger: Accessing `fastmcp.apps.<anything-other-than-FastMCPApp>` that is not an explicitly imported name, e.g. `from fastmcp.apps import FastMCPApp misspelled as FastmcpApp/AppFastMCP`, or `import fastmcp.apps; fastmcp.apps.some_helper`.

Common situations: Typos in imports after upgrading versions; assuming all public symbols are re-exported from the package __init__; IDE auto-import picking the package instead of the correct submodule; code written against an older/newer layout of the apps feature.

Related errors

• module {__name__!r} has no attribute {name!r}
• Setting {parent_attr} does not exist.
• Cannot resolve tool reference: {fn!r}
• Cannot specify both a name as first argument and as keyword
• First argument to @{decorator_name} must be a function, stri

AI-assisted analysis of PrefectHQ/fastmcp@1f02114297 (2026-08-29). Data as JSON: /api/errors/2bd492f4e24147bd. Report an issue: GitHub.