Colab MCP (Enhanced Fork)

An MCP server for controlling Google Colab from any AI coding agent. This fork fixes the bugs in the official repo that block real day-to-day use and restores features Google removed upstream.

Why This Fork?

Three concrete dolores that the official googlecolab/colab-mcp doesn't solve — and that this fork does:

1. Invisible tools (#54, #67, #69) — only open_colab_browser_connection appears in most MCP clients (Claude Code, Codex, Kiro IDE). The notebook tools rely on notifications/tools/list_changed, which these clients ignore. Without get_cells in particular, the bridge is effectively write-only: an agent can add cells but can't read state back.

2. "Disconnected from the local Colab MCP server" (#84) — orphaned servers from prior Claude Code sessions hold ports that your browser tab still points at. Reconnecting from the tab silently fails.

3. No programmatic GPU control — Google removed the --enable-runtime feature entirely. You can't assign T4 / L4 / A100 without clicking in the browser.

This fork fixes all three. All 9 tools (1 connection + 7 notebook + 1 GPU control) appear immediately, stale servers are auto-detected and clean-uppable, and GPUs are assignable from a single tool call.

Demo coming soon: docs/demo.gif (TODO — short asciinema of change_runtime → add_code_cell → run_code_cell).

Related MCP server: Colab MCP

What's Different

Available Tools

Note: execute_cell was renamed to run_code_cell in 2026-06-16 to match the browser-side handler name. Pass a cellId (from add_code_cell or get_cells) — the old cellIndex fallback was removed.

Quick Start (Without OAuth)

If you just want the notebook tools (no change_runtime):

1. Install uv

# Windows (PowerShell)
powershell -ExecutionPolicy ByPass -c "irm https://astral.sh/uv/install.ps1 | iex"

# Mac/Linux
curl -LsSf https://astral.sh/uv/install.sh | sh

Important: Do NOT use pip install uv — that version lacks required features.

2. Clone this repo

git clone https://github.com/SebastianGilPinzon/colab-mcp.git

3. Configure your MCP client

Add to your .mcp.json (Claude Code, Cursor, etc.):

{
  "mcpServers": {
    "colab-proxy-mcp": {
      "command": "uv",
      "args": ["run", "--directory", "/path/to/colab-mcp", "colab-mcp"],
      "timeout": 30000
    }
  }
}

4. Use it

1. Restart your editor / reload window

2. All 8 tools should appear immediately (open_colab_browser_connection + 7 notebook tools)

3. Call open_colab_browser_connection — a Colab notebook opens in your browser

4. Use add_code_cell, run_code_cell, get_cells, etc. to control the notebook

Full Setup (With OAuth + GPU Control)

This enables the change_runtime tool, which lets your agent assign GPUs without you touching the browser.

1. Create OAuth Credentials

You need a Google Cloud project with OAuth configured. This is a one-time setup (~5 minutes):

1. Create a GCP project (or use an existing one):

   gcloud projects create colab-mcp-oauth --name="Colab MCP OAuth"

2. Configure OAuth consent screen:

   • Go to OAuth consent screen

   • Select "External" > Create

   • App name: Colab MCP, add your email as support + developer contact

   • Save through all steps

3. Add yourself as test user:

   • On the consent screen page > "Test users" > Add your Google email

4. Create OAuth client ID:

   • Go to Credentials

   • Create Credentials > OAuth client ID > Desktop app

   • Download the JSON file

   • Save it somewhere safe (e.g., ~/.config/colab-oauth.json)

Note: OAuth Client IDs can only be created via the Cloud Console web UI. There is no CLI or API for this.

2. Configure MCP with OAuth

{
  "mcpServers": {
    "colab-proxy-mcp": {
      "command": "uv",
      "args": [
        "run", "--directory", "/path/to/colab-mcp",
        "colab-mcp",
        "--client-oauth-config", "/path/to/colab-oauth.json"
      ],
      "timeout": 30000
    }
  }
}

3. Authorize (first time only)

The first time the server starts, it opens your browser for Google OAuth consent. Sign in, click Allow, done. The token is cached at ~/.colab-mcp-auth-token.json and auto-refreshes — you won't be asked again.

4. Use it

Agent: change_runtime(accelerator="T4")
> Runtime changed to T4. Endpoint: gpu-t4-s-xxx

Agent: open_colab_browser_connection()
> Connected. Available notebook tools: add_code_cell, add_text_cell, get_cells, run_code_cell, update_cell, delete_cell, move_cell

Agent: add_code_cell(code="!nvidia-smi")
> {"cellId": "abc123", ...}

Agent: run_code_cell(cellId="abc123")
> Tesla T4, 15GB memory...

Agent: get_cells()
> [{"cellId": "abc123", "code": "!nvidia-smi", "outputs": [...]}]

CLI Reference

Once installed (via uv run or uvx git+https://github.com/SebastianGilPinzon/colab-mcp), the colab-mcp command supports these flags:

The server maintains a tiny registry at %LOCALAPPDATA%\colab-mcp\registry.json (Windows) or ~/.colab-mcp/registry.json (macOS/Linux). Each running instance writes a {pid, port, host, started_at} entry on startup and removes it on clean shutdown. Stale entries from crashed processes are pruned automatically the next time colab-mcp starts.

Troubleshooting

Tools don't appear after setup

• Make sure you're using this fork, not the official repo

• Only define colab-proxy-mcp in ONE .mcp.json file (not both global and project — dual definitions spawn two server instances and one dies silently)

• Restart your editor after changing .mcp.json

change_runtime returns "Runtime API not initialized"

• Check that --client-oauth-config is in your .mcp.json args

• Check that the OAuth JSON file exists at the specified path

• Look at the server logs for the specific error:

  # Find the latest log
  ls -t $TMPDIR/colab-mcp-logs-*/colab-mcp.*.log | head -1 | xargs cat

• A healthy log shows: INFO:Colab API client ready

• If you see WARNING:Failed to initialize Colab API client, check the error message

Windows: Port blocked error (WinError 10013)

Already fixed in this fork (changed to port 8085). If you still hit it, edit src/colab_mcp/auth.py and change OAUTH_SERVER_PORT to any open port.

OAuth says "Access denied"

Add your Google email as a test user in Cloud Console > OAuth consent screen > Test users.

Browser opens but connection times out

Make sure you have a Colab notebook open in the browser tab that opened. Click "Connect" if prompted.

Chrome reused an old Colab tab pointing at a dead port

Chrome dedupes tabs by URL canonical (ignoring the #fragment), so when an old Colab tab is still open with a fragment pointing at a previous server's port, calling open_colab_browser_connection again may silently focus the old tab instead of opening a fresh one. The old tab shows "Disconnected from the local Colab MCP server" and the new server times out.

This fork mitigates that by appending the current port as a query param (?p=<port>) to the Colab URL, so each server instance produces a unique URL that Chrome can't dedupe. If you still hit it after upgrading:

1. Close every colab.research.google.com tab in your browser.

2. Retry open_colab_browser_connection — it will open a fresh tab pointed at the live server.

Chrome silently blocks every connection attempt after one previous "Block"

If Chrome shows "Disconnected from the local Colab MCP server" on every attempt — including immediately after the page loads, with no permission prompt — and the server logs only stream ends after 0 bytes (TCP opens then closes without any HTTP request), the most likely cause is that you previously clicked "Block" on the Local Network Access prompt for colab.research.google.com. Chrome remembers that choice per site and never asks again — every WebSocket attempt is silently cancelled before the handshake. Edge / Firefox / other Chromium profiles are unaffected.

Fix (Chrome):

1. Open chrome://settings/content/siteDetails?site=https%3A%2F%2Fcolab.research.google.com

2. Find "Access other devices on the network" / "Acceder a otros dispositivos en la red" / Insecure content

3. Change from Block to Ask

4. Reload the Colab tab and accept the prompt when it appears.

Quickest reset (clears all Colab site permissions):

1. Open https://colab.research.google.com

2. Click the lock icon next to the URL

3. Click "Reset permissions" / "Restablecer permisos"

4. Reload and try again.

This was reproduced and root-caused with a manual E2E test (scripts/manual_browser_test.py): Edge connected on first attempt, Chrome timed out indefinitely until the per-site permission was reset.

Chrome asks for "Permission to access other services and apps on this device" (or Colab says "Disconnected")

When the Colab tab loads, Chrome shows a permission prompt:

colab.research.google.com wants — Permission to access other services and apps on this device

Click Allow. If you block it, the WebSocket connection from the Colab tab to your local colab-mcp server is blocked, the tab shows "Disconnected from the local Colab MCP server", and open_colab_browser_connection will time out.

This prompt is Chrome's Local Network Access policy: a public site (https://colab.research.google.com) is asking to talk to a resource on your local network (ws://localhost:<port> where colab-mcp is listening). Chrome blocks this by default and asks the user. The "other service" in the prompt is your own colab-mcp server running on your machine — not external access. The connection is scoped to a one-time token in the URL fragment (#mcpProxyToken=...), so even on the same machine other processes can't piggy-back on it.

Chrome remembers the choice per-site, so you only need to allow it once for colab.research.google.com.

"Disconnected from the local Colab MCP server" — IPv4/IPv6 dual-stack bind (root cause)

If you saw this message on the official googlecolab/colab-mcp and assumed it was an orphaned-server issue, the actual root cause is different — and is fixed in this fork.

With host="localhost" + port=0, the websockets library binds two sockets on different ephemeral ports (one for IPv6 ::1 and one for IPv4 127.0.0.1), then reports only one of them as the "server port". The Colab tab opens ws://localhost:<reported-port>, Chrome resolves localhost to either address family, and connects to a port with no listener in 50% of cases. The TCP connection drops with stream ends after 0 bytes server-side, the Colab tab shows "Disconnected from the local Colab MCP server" instantly, and the user waits 60s for a generic timeout.

This fork forces IPv4-only (host="127.0.0.1") so there is exactly one socket on exactly one port, and asserts this invariant at startup (raising RuntimeError if a future change re-introduces the dual-bind). See websocket_server.py and the tests test_single_socket_single_port / test_default_host_is_ipv4.

Orphaned colab-mcp processes (separate issue)

If a Colab tab in your browser shows "Disconnected from the local Colab MCP server" and re-clicking Connect doesn't help, the cause is almost always one or more orphaned colab-mcp processes from previous Claude Code sessions. Each instance picks a random ephemeral port, but your Colab tab only remembers the port from the URL fragment used when it first opened — when that server dies (or you spawn a new Claude Code session with a new server on a different port), the tab keeps trying to reach a dead address.

This fork ships with built-in diagnostics. Run any of these from a regular shell (not from inside Claude Code, which is itself running an MCP instance):

# Show every colab-mcp server currently registered as running
uv run --directory /path/to/colab-mcp colab-mcp --list-running

# Terminate orphaned colab-mcp servers, then exit
uv run --directory /path/to/colab-mcp colab-mcp --kill-stale

The server writes a small registry file at %LOCALAPPDATA%\colab-mcp\registry.json (Windows) or ~/.colab-mcp/registry.json (macOS/Linux) listing pid + port for each running instance. On every startup it prunes dead entries automatically, and on clean shutdown it removes its own. If open_colab_browser_connection times out from inside Claude Code, the new error message also includes the ports + pids of any peer servers so you can identify which one your browser tab is actually pointed at.

After cleaning up, re-run open_colab_browser_connection — it will open a fresh Colab tab pointed at the current (only) server's port + token.

Fixes upstream issue #84.

Compatibility

Tested with:

• Claude Code (VS Code extension + CLI)

• Should work with any MCP client that supports the standard tool protocol (Cursor, Windsurf, Codex, etc.)

Supported platforms:

• Windows 10/11

• macOS

• Linux

Changes from Upstream

This fork is based on googlecolab/colab-mcp with these changes:

• f70c00d Register notebook tools directly on the FastMCP server at startup (fixes invisible tools)

• cae498b Add change_runtime tool with OAuth for programmatic GPU assignment

• 440e3bc Fix ColabClient initialization (missing Prod() env arg) + change OAuth port to 8085 for Windows

• e66ee69 Match real Colab API signatures (language param, cellId, run_code_cell)

• stale-server detection Process registry + --list-running / --kill-stale flags + clearer timeout diagnostics — fixes upstream #84 "Disconnected from the local Colab MCP server"

• full 7-tool notebook surface — pre-register get_cells, delete_cell, move_cell (previously missing) and rename execute_cell → run_code_cell to match the browser-side handler. Closes upstream #69.

Google does not accept external contributions to the official repo, so these fixes live here.

Verified fixes (accepted in upstream discussions)

• #67 → answered — invisible-tools fix (this fork's pre-registration approach was accepted by the upstream community as the working solution).

• #69 — follow-up on get_cells and the remaining missing stubs — addressed in this fork on 2026-06-16.

• #84 — "Disconnected from the local Colab MCP server" — addressed via the stale-server registry + --kill-stale CLI.

License

Apache 2.0 (same as upstream)

⭐ If this fork saved you time, a star helps others find it.