# Kill Stale MCP

> Kill stale/orphaned MCP server processes leaked by ended sessions — npx-launched servers (chrome-devtools-mcp, sentry-mcp, any npm exec *mcp*), their wrappers and watchdogs — while keeping the ones live sessions are using. Use when MCP processes pile up across sessions and eat memory.

- Skill: `hamid-bhz/kill-stale-mcp` (Agent Skill)
- Install (CLI): `npx skillmds@latest add hamid-bhz/kill-stale-mcp`
- Raw SKILL.md: https://api.skillmd.com/api/skills/hamid-bhz/kill-stale-mcp/raw
- Safety review: pending (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: AI & ML
- Author: hamid-bhz (https://skillmd.com/u/hamid-bhz)
- Updated: 2026-09-22
- Page: https://skillmd.com/skills/hamid-bhz/kill-stale-mcp

---


# /kill-stale-mcp

npx-launched MCP servers leak. The launch chain is `npm exec <server>@...` → server → (sometimes) a telemetry watchdog. When a session ends uncleanly, the termination signal stops at the `npm exec` wrapper — npx does not forward it to its children — so the whole group keeps running. Every dead session leaves one group behind (~100–250 MB each).

This skill kills the **stale** groups and keeps the **live** ones.

**Staleness test:** a live group's `npm exec` wrapper is parented to a running host process (Claude Code, an IDE extension host). When the host dies, the orphaned processes are re-parented to PID 1 (`launchd` on macOS, `init`/`systemd` on Linux). **PPID 1 → stale. PPID = a live host → in use, keep.**

## Steps

1. List every MCP-related process with its parent PID:

   ```bash
   ps -eo pid,ppid,lstart,command | grep -i mcp | grep -v grep
   ```

2. Classify each process:
   - **Not ours — never touch:** anything owned by an IDE or app rather than launched via npx (e.g. Cursor `mcp-process`, GitLens/GitKraken `gk mcp`, Electron app helpers). Only handle processes whose command contains `npm exec` or a `~/.npm/_npx/` path, plus their direct children.
   - **Stale:** an npx-launched process with `PPID 1`; or a watchdog whose `--parent-pid=<N>` is dead (check with `kill -0 <N>`).
   - **Live:** the wrapper's PPID is a running session process. Keep the whole group.

3. Kill the stale PIDs explicitly (never `pkill -f mcp` — that would take down live sessions' servers and IDE-owned processes):

   ```bash
   kill <stale pids...>
   ```

4. Re-run the listing from step 1. Killing a wrapper re-parents its children to PID 1, so they now show up as stale themselves — repeat step 3 until no npx-launched process with PPID 1 remains.

5. Report: how many groups were killed (with spawn times) and which live groups were kept.

## Notes

- Live servers respawn on demand the next time a session uses them — this skill removes leaked instances, it does not disable any MCP.
- Root cause is npx signal handling. If one server leaks constantly, launch it directly by its bin path in the MCP config instead of via `npx`.