High CPU usage when idle (10-90% per instance)

Description

Claude Code uses significant CPU (10-90% per instance) even when completely idle and waiting for user input. This becomes problematic when running multiple instances.

Environment

• Claude Code version: 2.1.27
• OS: Linux (Ubuntu)
• Node: v22.22.0

Observed Behavior

Running top shows Claude Code processes consuming 50-100% CPU each while doing nothing - just displaying a prompt waiting for input.

PID    USER  %CPU  COMMAND
2931058 devin 109.1 claude
3568968 devin  90.9 claude
2915221 devin  63.6 claude
3223647 devin  54.5 claude

Expected Behavior

An idle CLI waiting for input should use minimal CPU (<1%).

Suspected Causes

1. Node.js event loop running without sleeping
2. Ink terminal UI doing unnecessary redraws
3. File watchers or polling mechanisms
4. Background services staying warm

Impact

Users running multiple Claude Code instances (e.g., for agent orchestration) see significant system resource consumption even when agents are idle.

Workaround

Currently none - killing idle instances is the only mitigation.