issue: mcpo errors while starting (maybe dependency-issues with mcp2?)

[lineg-it]

Check Existing Issues

• I have searched the existing issues and discussions.
• I am using the latest version of mcpo.

mcpo Version

0.0.20

Open WebUI Version (if applicable)

Operating System

Debian 13

Browser (if applicable)

No response

Confirmation

• I have read and followed all instructions in README.md.
• I am using the latest version of both MCPO and Open WebUI.
• I have included the browser console logs.
• I have included the Docker container logs.
• I have listed steps to reproduce the bug in detail.

Expected Behavior

Mcpo starts, installs dependencies and starts a listener.

Actual Behavior

mcpo doesnt start in the first place.

Steps to Reproduce

1. start mcpo via:

uvx mcpo --port 18000 --api-key "<redacted>" --config ./config.json --hot-reload

Logs & Screenshots

╭───────────────────────────────────────────────────────────── Traceback (most recent call last) ───────────────────────────╮
│ /home/loginuser/.cache/uv/archive-v0/ev7leLIhOjDiG_9T/lib/python3.13/site-packages/mcpo/__init__.py:93 in main            │
│                                                                                                                           │
│    90 │   │   │   typer.echo("Error: You must specify the MCP server command after '--'")									│
│    91 │   │   │   return									 																│
│    92 │																													│
│ ❱  93 │   from mcpo.main import run									 													│
│    94 │									 																				│
│    95 │   if config_path:									 																│
│    96 │   │   print("Starting MCP OpenAPI Proxy with config file:", config_path)									 		│
│									 																						│
│ /home/loginuser/.cache/uv/archive-v0/ev7leLIhOjDiG_9T/lib/python3.13/site-packages/mcpo/main.py:20 in <module>			│
│									 																						│
│    17 from mcp import ClientSession, StdioServerParameters																│
│    18 from mcp.client.sse import sse_client																				│
│    19 from mcp.client.stdio import stdio_client																			│
│ ❱  20 from mcp.client.streamable_http import streamablehttp_client									 						│
│    21									 																					│
│    22 from mcpo.utils.auth import APIKeyMiddleware, get_verify_api_key									 				│
│    23 from mcpo.utils.main import (									 													│
╰───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────╯
ImportError: cannot import name 'streamablehttp_client' from 'mcp.client.streamable_http' (/home/loginuser/.cache/uv/archive-v0/ev7leLIhOjDiG_9T/lib/python3.13/site-packages/mcp/client/streamable_http.py)

Additional Information

EDIT: The docker image of mcpo starts perfectly, but refuses to load and start several mcp-servers, which more or less correlates to the fact that mcp v2 changed many things

Workaround for failing mcp-servers within mcpo on Docker:

Add --with mcp<2 to your uvx arguments for any affected mcp-server:

For example to fix (affected) @modelcontextprotocol/fetch, open config.json and add two lines as follows:

"fetch": {
      "command": "uvx",
      "args": [
        "--with",                      #<- 1.
        "mcp<2",                     # <- 2.
        "mcp-server-fetch"
      ]
    },

Source: modelcontextprotocol/servers#4560

[aciapetti]

It happens to me, too!

[freerainboxbox]

Temporary fix before a PR is merged:

uvx --with "mcp<2" mcpo --port 8000 --api-key "top-secret" -- your_mcp_server_command

That should pin a previous version without having to change any code.

[av]

Independently reproduced while integrating mcpo into Harbor (https://github.com/av/harbor): fresh uvx mcpo resolves mcp 2.0.0 (mcpo 0.0.20 declares mcp>=1.17.0) and crashes at startup with ImportError: cannot import name 'streamablehttp_client' from 'mcp.client.streamable_http' — the import was removed in the mcp 2.x major.

Reliable workaround at the mcpo level (no per-server pins needed): uvx --with 'mcp<2' mcpo ... (resolves mcp 1.29.0, everything works) — that's what Harbor ships now (av/harbor@5b90147).

Proper fix would be an upper bound in mcpo's dependency metadata (mcp>=1.17.0,<2) until mcpo is ported to the 2.x API.