open_colab_browser_connection returns false - missing URL parameters

[whoami4101]

open_colab_browser_connection returns false - missing URL parameters

Problem

open_colab_browser_connection returns false even though browser opens successfully. The WebSocket connection fails because URL parameters are missing.

Setup

• OS: Linux (Ubuntu)
• uv: 0.9.7
• MCP Client: Kiro IDE

Config:

{
  "mcpServers": {
    "colab-mcp": {
      "command": "uvx",
      "args": ["git+https://github.com/googlecolab/colab-mcp", "--enable-proxy"],
      "timeout": 30000
    }
  }
}

What Happens

1. Call open_colab_browser_connection
2. Browser opens to https://colab.research.google.com/notebooks/empty.ipynb
3. Tool returns false

Expected vs Actual

Expected: URL should include #mcpProxyToken=TOKEN&mcpProxyPort=PORT
Actual: URL has no connection parameters

Investigation

• ✅ Server starts and binds WebSocket ports
• ✅ Browser opens successfully
• ❌ URL missing mcpProxyToken and mcpProxyPort parameters
• ❌ No WebSocket connection established

Root Cause

The browser URL generation isn't including the token/port parameters needed for WebSocket connection back to the local MCP server.

[xiaods]

yes, invoke open_colab_browser_connection failed.

[kiwamizamurai]

yes

[cuffjosie]

@xiaods @kiwamizamurai are you both also on Kiro IDE?
could you share your client if not?

[kiwamizamurai]

I'm using Claude Code as the MCP client

{
"colab-mcp": {
"command": "uvx",
"args": ["git+https://github.com/googlecolab/colab-mcp"],
"timeout": 30000
}
}

[cuffjosie]

for Claude Code you may need type too

{
  "mcpServers": {
     "colab-mcp": {
        "type": "stdio",
        "command": "uvx",
        "args": ["git+https://github.com/googlecolab/colab-mcp"],
        "timeout": 30000
      }
  }
}

could you confirm that you are getting the same behavior as the top comment?

1. the MCP server starts
2. the open_colab_browser_connection tool is run by Claude
3. the browser opens to a Colab URL, but does not have #mcpProxyToken=TOKEN&mcpProxyPort=PORT

[rafaelgildin]

@cuffjosie
even by having this configuration, I'm experiencing a lot of latency for the connection. trying to check what it could be.

[cuffjosie]

@rafaelgildin is your browser opening successfully? is the latency seen while trying to establish a browser connection or after the connection is established?

[rafaelgildin]

yes. @cuffjosie I just did some adjustments in the MCP side to enable opening any existing colab notebook.

[cdundes-sb]

@rafaelgildin mind sharing what adjustments you made?

[Lalas-dev]

Whats next

[devferrazZz]

I managed to run with OpenCode

I was getting this problem and that's what I did that fixed it:

• I'm using opencode v1.3.17 on Mac
• I added the mcp confg server in opencode.json file, in the project root folder as:

{
  "$schema": "https://opencode.ai/config.json",
  "mcp": {
    "colab_mcp": {
      "type": "local",
      "command": [
        "uvx",
        "git+https://github.com/googlecolab/colab-mcp"
      ],
      "timeout": 30000,
      "enabled": true
    }
  }
}

• Closed and re-opened openCode
• Asked the agent to: "open a colab notebook using colab_mcp tool"
• It then opens a new tab in chrome browser with the expected url format: #mcpProxyToken=TOKEN&mcpProxyPort=PORT
• The colab notebook will prompt you to click Connect — there's Advanced Options but I didn't play with it. This is to use the generated token in another colab session, because the agent will always start a blank new colab notebook.
• Once you connect within the timeout it should work

To connect with an existent notebook:

1. Once you connect with the blank notebook hit Cmd+Shift+P to bring Colab's command palette and type: mcp
2. This will fetch the Connect to MCP server — something like this — option, open it.
3. Click Advanced Options: this will give you the {toke}&{port} string format to copy and paste in another Colab notebook
4. Go to the notebook of your choice, repeat steps 1. and 2. But this time it will prompt for the token+port you copied on 3.
5. Paste it. Now your agent has access to this other notebook, the previous gets disconnected.

Hope it helps!

[SebastianGilPinzon]

Hit this exact issue, open_colab_browser_connection returns false and the tab never connects.

For me it was two server bugs: ColabClient initialized without the Prod() env arg, and on Windows the proxy port (53919) is blocked (WinError 10013), so the token/port never made it into the URL fragment.

Patched both in a fork (also pre-registered the notebook tools so they show up immediately): https://github.com/SebastianGilPinzon/colab-mcp, happy to help if anyone tries it and still hits the false.