Zombie MCP plugin servers peg CPU for days
Investigating why a workstation was running at extreme load average while seemingly idle, blocking unrelated GPU workloads.
Claude Code plugin servers (bun-based MCP servers for things like messaging integrations) can outlive their spawning session and get stuck in busy loops, pegging 99% CPU per zombie for many days. They look legitimate in ps because the command line is just 'bun server.ts'; their parent wrapper processes are gone but the child keeps running. Multiple stacked zombies trivially saturate a laptop's perf cores and silently sabotage anything else that needs CPU/GPU (e.g. local Whisper transcription, builds).
On any unexplained high load, immediately run 'ps -eo pid,%cpu,etime,command | grep -E "bun.*server.ts" | sort -k2 -rn' to surface orphan MCP servers older than the current session — they will not show up via dock/menu UI and are easy to miss.