BerriAI/litellm · error · HTTPException

MCP stdio command '{server.command}' is not in the allowlist

Error message

MCP stdio command '{server.command}' is not in the allowlist ({sorted(MCP_STDIO_ALLOWED_COMMANDS)}). Add it to LITELLM_MCP_STDIO_EXTRA_COMMANDS to allow this command.

What it means

Error "MCP stdio command '{server.command}' is not in the allowlist ({sorted(MCP_STDIO_ALLOWED_COMMANDS)}). Add it to LITELLM_MCP_STDIO_EXTRA_COMMANDS to allow this command." thrown in BerriAI/litellm.

Source

Thrown at litellm/proxy/_experimental/mcp_server/mcp_server_manager.py:3301

            # or be read-only, causing npx to fail with ENOENT.
            if resolved_env is not None and "NPM_CONFIG_CACHE" not in resolved_env:
                resolved_env["NPM_CONFIG_CACHE"] = MCP_NPM_CACHE_DIR
            # Defense-in-depth: block commands not in the allowlist.
            # The Pydantic validator blocks new servers; this catches legacy
            # config/DB records predating the allowlist.
            if server.command:
                base_command: Final = os.path.basename(server.command)
                # Strip .exe/.cmd/.bat/.com suffix for Windows compatibility
                base_command_no_ext = base_command.lower()
                for ext in [".exe", ".cmd", ".bat", ".com"]:
                    if base_command.lower().endswith(ext):
                        base_command_no_ext = base_command[: -len(ext)].lower()
                        break
                if (
                    base_command.lower() not in MCP_STDIO_ALLOWED_COMMANDS
                    and base_command_no_ext not in MCP_STDIO_ALLOWED_COMMANDS
                ):
                    raise HTTPException(
                        status_code=403,
                        detail=f"MCP stdio command '{server.command}' is not in the allowlist ({sorted(MCP_STDIO_ALLOWED_COMMANDS)}). "
                        f"Add it to LITELLM_MCP_STDIO_EXTRA_COMMANDS to allow this command.",
                    )

            stdio_config: MCPStdioConfig | None = None
            if server.command and server.args is not None:
                stdio_config = MCPStdioConfig(
                    command=server.command,
                    args=server.args,
                    env=resolved_env,
                )

            return MCPClient(
                server_url="",  # Not used for stdio
                transport_type=transport,
                auth_type=server.auth_type,
                auth_value=auth_value,

View on GitHub (pinned to 77b7c6c40c)

Solutions

1. Add the command to LITELLM_MCP_STDIO_EXTRA_COMMANDS.
2. Or use an allowlisted stdio command.

Example fix

export LITELLM_MCP_STDIO_EXTRA_COMMANDS='mycommand'

When it happens

Trigger: Thrown at litellm/proxy/_experimental/mcp_server/mcp_server_manager.py:3301 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of BerriAI/litellm@77b7c6c40c (2026-08-18). Data as JSON: /api/errors/c8f136da736db6b3. Report an issue: GitHub.