"Disconnected from the local Colab MCP server"

[erichuang777777]

I had connected to colab via claude code yesterday and a training mission was complete.
However, i tried to resume my project. the connection pop out and I hit the "connect" bottom.
it shows "Disconnected from the local Colab MCP server" keep showing today.

I work on windows.
MCP setting is the same.

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

I tried in seperate terminal and fastmcp sucess, which showing colab MCP serever is running.

claude will use the tool "open_colab_browser_connection"
however, returning back to claude code, colab session could not be reached.
I also try to use The auth token and paste to other notebook, "Disconnected from the local Colab MCP server" pop out.

any ideas for solving these problem? quit annoying.
Need any kind of suggestion. Thank you very much.

[SebastianGilPinzon]

Did you found the solution? I can help you with it, I'm the aouthor of the fork 69 and it works for me

[erichuang777777]

Thank you for the information. It turns out to be several MCP server was started After I shut down other server, it work. However, it happens some time In recent days. Please share your experience. Since I’m not an engineer. It bothers me a lot. Sebastian Gil Pinzon ***@***.***>於 2026年5月13日週三，23:34寫道：

…

Did you found the solution? I can help you with it, I'm the aouthor of the fork 69 <#69> and it works for me — Reply to this email directly, view it on GitHub <#84 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/BQVPTEOHGVGDXJWDJWRBWTL42SIWPAVCNFSM6AAAAACYH7UPYCVHI2DSMVQWIX3LMV43URDJONRXK43TNFXW4Q3PNVWWK3TUHMYTMOJQGY4TAMQ> . You are receiving this because you authored the thread.Message ID: ***@***.***>

[SebastianGilPinzon]

Hi @erichuang777777, glad you figured out the "multiple MCP servers running" angle — that's exactly the root cause.

Quick recap of what's happening under the hood:

• Every time uvx starts the colab-mcp server it binds to a random ephemeral
  port (the upstream code passes port=0 to websockets.serve).
• The Colab tab in your browser only knows the port from the URL fragment that
  was used when it first opened (e.g. #mcpProxyToken=...&mcpProxyPort=54366).
• When that server dies — Claude Code crashes, you close the editor, you start
  a new session that spawns a fresh MCP server on a different port — the tab
  keeps trying to reach the old, now-dead port. Result: "Disconnected from the
  local Colab MCP server", forever.
• And because nothing in upstream tracks which colab-mcp processes are
  running, you also can't tell if there are orphans lying around without
  digging through Task Manager / ps.

I just shipped a fix for this in my fork:
https://github.com/SebastianGilPinzon/colab-mcp

It adds:

• A tiny process registry at %LOCALAPPDATA%\colab-mcp\registry.json
  (Windows) or ~/.colab-mcp/registry.json that tracks each running
  instance's PID and port. Dead entries are pruned automatically on startup,
  and clean shutdown removes the server's own entry.
• Two new CLI flags you can run from a regular shell (NOT from inside Claude
  Code, which is itself an MCP client):
  colab-mcp --list-running # show all currently-running colab-mcp servers
  colab-mcp --kill-stale # terminate orphans and exit
• A clearer error message when open_colab_browser_connection times out —
  it now tells you this server's port + the PIDs/ports of any peer
  colab-mcp processes, so you can identify which one your browser tab is
  pointing at.

To try it, just swap the upstream URL in your mcp.json:

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