MCP servers imported from ~/.claude.json, ~/.codex/config.toml or .mcp.json fail to start in chats (missing launcher, ENOENT)

Open
  • Is something wrong?
#766 0 comments 0 reactions 0 assignees View on GitHub

Maintainers usually reply within 1 day

Nobody has claimed this yet.

Assessment

Difficulty
3/5
Estimated time
1-2 days
Newbie friendliness
68/100
Issue type
Bug
Clarity
Clearly specified
Activity status
Active
Tech stack
typescript
Domain
ai-infra-agents, backend

Research direction

Start in packages/agent-app/src/runtime/domains/mcp.ts, especially syncDetected() and the thread-config builder around line 304; compare them with the add and update handlers that call writeLauncher(). Trace how detected entries are stored and how launcher scripts are generated, then check that new and changed stdio servers with arguments use launchers matching their current settings. Done when the acceptance cases work for Claude Code, Codex, and folder .mcp.json sources.

Written by the indexing model from the issue text.

Description

Problem

MCP servers that Muster detects from ~/.claude.json, ~/.codex/config.toml or a folder's .mcp.json fail to start in a chat when they are stdio servers with arguments, which covers almost every npx … or uvx … server. The agent reports them as failed with ENOENT (Claude Code, for example, shows posix_spawn '…/mcp-launchers/<id>.sh'). Settings › MCP servers still shows the same servers as healthy, because its own test starts the command directly.

Turning a server off and on in Settings makes it work, because that writes its launcher. The bug comes back for any server detected later.

Cause

In packages/agent-app/src/runtime/domains/mcp.ts:

  • The thread config points every stdio server with arguments at its launcher script, <dataDir>/mcp-launchers/<id>.sh (line 304): 
    configOverrides[`${key}.command`] = entry.args.length ? launcher(entry.id) : entry.command;
  • Only the add and update handlers call writeLauncher() (lines 332 and 340).
  • syncDetected() (line 123) stores detected servers but never writes their launcher. A new detected server therefore has no script. A detected server whose command or arguments change keeps a stale script that still runs the old command.

Expected

  • Every stdio server with arguments that is handed to an agent has a launcher matching its current command and arguments, whatever its source (Settings, ~/.claude.json, ~/.codex/config.toml, .mcp.json).
  • For example, syncDetected() could call writeLauncher() for new or changed entries, or the thread-config builder could write the launcher when it is missing or out of date before it uses the path.

Acceptance

  1. With a fresh data folder and a stdio server with arguments in ~/.claude.json (e.g. npx -y @modelcontextprotocol/server-memory), a new Claude Code chat lists the server as connected and can call its tools, without anyone opening Settings.
  2. The same works for a server in ~/.codex/config.toml in a Codex chat, and for one in a folder's .mcp.json.
  3. Changing a detected server's arguments in its source file makes the next chat start it with the new arguments.

Seen on Muster Agent 0.3.14 and 0.3.15 (Linux, Arch) and still present on main (b2c9d8836).

Dominant language
TypeScript
Stars
3
Forks
0
Avg merge
17h 33m
Merged PRs (30d)
163

Getting set up

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

More from musterhq/muster-code

All issues in musterhq/muster-code

Similar issues

More TypeScript issues

Get new issues in your inbox

A short digest of beginner-friendly GitHub issues.