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kill-stale-mcp

kill-stale-mcp is a skill for Claude Code from hamid-bhz/claude-skills. It costs 71 tokens per session (650 once invoked), scanned A, original, MIT.

A cleanup skill for finding and stopping abandoned MCP server processes. MCP servers are background programs that give an agent extra tools.

In plain words
What is it for?
Use it when MCP processes accumulate, memory use grows, or old agent sessions may have left servers running.
Why use it?
Ended sessions can leave these programs running and consuming memory. The skill distinguishes abandoned processes from ones still used by active sessions.

Skill for Claude Code

Written for Claude Code: shipped in a Claude Code plugin. Also seen: mentions Claude Code.

Part of the mcp-toolkit plugin — 1 skill shipped together

not rated 3repo 3mo ago A scan 71 tokens original MIT

Good fit Use it when MCP processes accumulate, memory use grows, or old agent sessions may have left servers running.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/hamid-bhz/claude-skills/kill-stale-mcp
View source ↗ hamid-bhz/claude-skills
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add hamid-bhz/claude-skills --skill kill-stale-mcp
Clone the repo
git clone --depth 1 https://github.com/hamid-bhz/claude-skills

Made for: Claude Code.

Or install mcp-toolkit, the plugin that ships this one along with the rest of its 1 skill.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for kill-stale-mcp

README.md
[![agentmods](https://agentmods.dev/badge/skills/hamid-bhz/claude-skills/kill-stale-mcp/github.svg)](https://agentmods.dev/skills/hamid-bhz/claude-skills/kill-stale-mcp)
Your own site
<a href="https://agentmods.dev/skills/hamid-bhz/claude-skills/kill-stale-mcp"><img src="https://agentmods.dev/badge/skills/hamid-bhz/claude-skills/kill-stale-mcp/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for kill-stale-mcp

Your own site · 80×15
<a href="https://agentmods.dev/skills/hamid-bhz/claude-skills/kill-stale-mcp"><img src="https://agentmods.dev/badge/skills/hamid-bhz/claude-skills/kill-stale-mcp.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 71 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 650 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00071 $0.00650
Opus 5.5 $0.00028 $0.00260
Sonnet 5.5 $0.00014 $0.00130
Haiku 4.5 $0.00007 $0.00065

Measured 2mo ago against content hash 9bef98cd3a9b, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

kill-stale-mcp scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2mo ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

plugins/mcp-toolkit/skills/kill-stale-mcp/SKILL.md · 41 lines

How it starts

The opening of the file, as written. The whole thing — 41 lines — stays where its author put it; the contents beside it link to each section on GitHub.

/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:

    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):

    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.

Read the full file on GitHub · 41 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2mo ago First seen · 41 lines · 71 tokens per session scan A 9bef98cd3a9b

Subscribe to this mod's changes

kill-stale-mcp is a skill published in the GitHub repository hamid-bhz/claude-skills (3 stars, last pushed 3mo ago), licensed MIT. It adds 71 tokens to every session and 650 once invoked, about $0.0003 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

Claude CodeDevOps and cloudai-agentsclaudemcpskills
Related

kill-stale-mcp compared with skills from other repositories

kill-stale-mcp next to 6 skills from other repositories
ModTypeStarsLast pushLicenceScanTokensWorks with
kill-stale-mcphamid-bhz/claude-skillsSkill33mo agoMITA71Claude Code
claude-md-improveranthropics/claude-plugins-officialSkill47ktodayApache-2.0A82Claude Code
agent-platform-model-registrygoogle/skillsSkill24ktodayApache-2.0A60Claude Code, Codex
gke-reliabilitygoogle/skillsSkill24ktodayApache-2.0A85Claude Code, Codex
gke-workload-securitygoogle/skillsSkill24ktodayApache-2.0A171Claude Code, Codex
google-cloud-solution-agentic-analytics-spark-knowledge-cataloggoogle/skillsSkill24ktodayApache-2.0A132Claude Code, Codex
glance-canonical-layoutsandroid/skillsSkill10k2d agoApache-2.0A56Claude Code