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Codex Issues / #23441

Colab MCP only exposes `open_colab_browser_connection`; notebook tools never appear in Codex Desktop after connection

Open 💬 1 comment Opened May 19, 2026 by neonvarun

Colab MCP only exposes open_colab_browser_connection; notebook tools never appear in Codex Desktop after connection

Summary

Google Colab MCP is installed correctly and launches on Windows, but in Codex Desktop only the bootstrap tool open_colab_browser_connection is exposed. After connecting a live Colab notebook, the richer notebook tools expected from Colab MCP still never appear in the active thread.

This looks like a Codex Desktop or app-server MCP dynamic tool refresh problem rather than a bad local Colab MCP install.

Environment

  • Codex Desktop: desktop app session
  • Platform: Windows 11 10.0.26200
  • Python: 3.14.3
  • MCP config location: C:\Users\USER\.codex\config.toml
  • MCP server: googlecolab/colab-mcp
  • Launcher: uvx

MCP config

[mcp_servers.colab-mcp]
command = "uvx"
args = ["git+https://github.com/googlecolab/colab-mcp"]
enabled = true

Expected behavior

Per the Colab MCP announcement and upstream repo, after a Colab browser session connects, Codex should be able to use notebook tools such as:

  • add_code_cell
  • add_text_cell
  • delete_cell
  • get_cells
  • move_cell
  • run_code_cell
  • update_cell

Actual behavior

  • Codex exposes open_colab_browser_connection
  • That connection flow works
  • After connection, the richer notebook tools never appear in the thread

Why this looks like a Codex-side issue

The local Colab MCP install appears healthy:

  1. The launcher works:
uvx git+https://github.com/googlecolab/colab-mcp -h
  1. The config matches the upstream documented minimal setup.
  1. The upstream Colab MCP README explicitly says:
This MCP server requires client support for notifications/tools/list_changed
  1. The upstream Colab MCP source sends send_tool_list_changed() when Colab session connectivity changes.

That strongly suggests the real notebook tools are expected to appear dynamically after browser connection. The exact observed symptom is:

  • bootstrap tool is present
  • dynamic post-connection tools are missing

which points to a client-side refresh or thread injection gap.

Minimal repro

  1. Add this to C:\Users\USER\.codex\config.toml:
[mcp_servers.colab-mcp]
command = "uvx"
args = ["git+https://github.com/googlecolab/colab-mcp"]
enabled = true
  1. Restart Codex Desktop.
  2. Start a new thread.
  3. Confirm that open_colab_browser_connection is available.
  4. Open a live Colab notebook in the browser.
  5. Call open_colab_browser_connection.
  6. Observe that notebook CRUD/run tools still do not appear.

Suspected failure point

One of these layers seems to be failing:

  • Codex does not fully support or honor notifications/tools/list_changed
  • Codex receives the updated tool list but does not inject it into the live thread
  • Codex Desktop/app-server exposes only the initial bootstrap tool surface

Additional context

This fits the shape of other Codex MCP exposure bugs where MCP servers are discovered correctly but their tools are not surfaced into active threads.

References

View original on GitHub ↗

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