MCP server that dies after connecting shows "connected" forever and is never reconnected
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Assessment
- Difficulty
- 2/5
- Estimated time
- 1-3 hours
- Newbie friendliness
- 72/100
- Issue type
- Bug
- Clarity
- Clearly specified
- Activity status
- Active
- Tech stack
- typescript
- Domain
- backend
Research direction
Start in src/main/tools/mcp.ts, especially McpHub.connectOne and the client state handling described in the issue. Check how the MCP SDK signals a closed connection, then add a stdio fixture that exits after listTools. Done when status() reports an error after the server exits and refresh() reconnects.
Written by the indexing model from the issue text.
Description
Found in the 2026-10-07 code review (traced through MCP SDK 1.31.0).
Problem
McpHub.connectOne (src/main/tools/mcp.ts:100-141) never sets client.onclose. When a stdio server crashes or an HTTP session drops, the SDK clears its transport (protocol.js:268) and later calls throw Not connected. state.client stays set, though:
status()reportsconnected.- The tools are still offered to the model, and every call fails.
connectOnereturns early for an unchanged config, so a refresh doesn't reconnect either.
Fix
client.onclose = () => {
if (state.client !== client) return;
state.client = null;
state.tools = [];
state.listed = [];
state.error = 'The server closed the connection.';
this.onToolsChanged();
};
Optionally reconnect on the next refresh. Test: a stdio fixture that exits after listTools → status() reports an error and refresh() reconnects.
- Dominant language
- TypeScript
- Stars
- 2
- Forks
- 2
- Avg merge
- 5h 28m
- Merged PRs (30d)
- 24
Getting set up
- No Dockerfile or Docker Compose file
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- Read the contributing guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
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