entropy

Reclaim the machine.

Coding agents start things and walk away. Headless browsers that outlive their session, dev servers from last week, a review broker for every repo you've touched, worktrees nobody remembers, and caches that only ever grow. I had to kill about 200 stray Chrome processes by hand before I went looking.

Entropy is a skill for Claude Code and Codex. It checks known locations on your Mac, shows what's taking space, who owns it and what's grown since last time. Recommendations come with a reason and the cost of rebuilding or downloading things again. You pick what goes.

Install

With Node.js installed:

npx skills add noeltock/entropy -g

Pick your agent in the installer. -g makes the skill available across projects. To install for both Claude Code and Codex directly:

npx skills add noeltock/entropy -g -a claude-code codex

Or clone it manually:

git clone https://github.com/noeltock/entropy.git ~/.claude/skills/entropy
ln -s ~/.claude/skills/entropy ~/.codex/skills/entropy   # Codex, optional

Use

Run /entropy in Claude Code or Codex. It leads with recommendations, then the table and details. Reply with row IDs like E1 E4, or safe for the ● recommended rows only. ○ optional rows and ◆ review-first rows need explicit IDs; held rows stay held. Listed sizes aren't promised savings. Unknown sizes stay unknown.

/entropy                  scan, then reply with IDs (E1 E4) or "safe"
/entropy --all            include the small stuff
/entropy --held           show everything it won't touch, and why
/entropy --deep           the slow scans, when you actually want them
/entropy --host <ssh>     same scan on another Mac

Installing the skill doesn't run a scan or clean anything. After cleanup, it scans again and shows what's gone and how much disk space changed.

What it won't do

Touch a worktree with uncommitted or unpushed work, prune Docker volumes, delete a Docker Desktop disk before checking what's inside, kill a browser another session is still using, or act on anything you didn't pick. Caches go through each tool's own clean command, so nothing sits in the Trash pretending to be free space.

Tuning

Paths and time budgets live at the top of scripts/entropy.sh (override any of them with ENTROPY_* env vars). A new culprit is one line in references/culprits.tsv.

Evals

bash evals/run.sh --no-agent checks sizing, recommendations and safety without a model. Drop --no-agent to also run the agent scenarios through claude -p against a fake home folder, with every delete swapped for a logger. That part costs tokens. More in evals/README.md.

macOS only. It won't beat the second law, but it slows it down.