cmux CLAUDE.md

cmux CLAUDE.md is an instructions file for coding agents from craigsc/cmux. It costs 673 tokens per session, scanned A, original, MIT.

Repository instructions for Claude Code, an AI coding assistant, explaining cmux and the project’s files, structure, and shell commands. cmux is a Bash tool that gives each parallel coding session its own Git worktree, an isolated copy of the project files.

In plain words
What is it for?
Understanding and modifying the cmux codebase, including its shell functions, Git worktree handling, file layout, and command conventions.
Why use it?
It gives the assistant the project context and working rules it needs to make changes safely. Separate worktrees prevent parallel sessions from overwriting each other’s files.

Instructions file

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.

agentmods
npx agentmods add instructions/craigsc/cmux/claude-md
Clone the repo
git clone --depth 1 https://github.com/craigsc/cmux

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 cmux CLAUDE.md

README.md
[![agentmods](https://agentmods.dev/badge/instructions/craigsc/cmux/claude-md.svg)](https://agentmods.dev/instructions/craigsc/cmux/claude-md)
Your own site
<a href="https://agentmods.dev/instructions/craigsc/cmux/claude-md"><img src="https://agentmods.dev/badge/instructions/craigsc/cmux/claude-md.svg" alt="Measured on agentmods" height="20"></a>
Per session 673 This file is loaded in full into every session.
When invoked 673 The same file — it is already loaded in full.
Security scan A 1 finding. Scan, not verified.
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 $0.00673 $0.00673
Opus 5 $0.00336 $0.00336
Sonnet 5 $0.00135 $0.00135
Haiku 4.5 $0.00067 $0.00067

Measured 5d ago against content hash 796eb0e0f181, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

cmux CLAUDE.md scanned grade A with 1 finding 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 5d 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.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

- `install.sh` — curl-pipe installer that downloads cmux.sh to `~/.cmux/` and adds source line to shell RC
CLAUDE.md · 50 lines

How it starts

The opening of the file, as written. The whole thing — 50 lines — stays where its author put it; the contents beside it link to each section on GitHub.

CLAUDE.md

This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.

What is cmux

cmux is a pure Bash shell tool that manages git worktree lifecycles for running parallel Claude Code sessions. Each worktree gets its own isolated working directory so multiple Claude agents can work on the same repo simultaneously.

Architecture

Single-file shell tool — all logic lives in cmux.sh (~560 lines), which is sourced into the user's shell (bash/zsh). There is no build step, no dependencies, and no test suite.

Function structure:

  • cmux() — public dispatcher, routes subcommands to _cmux_<cmd> functions
  • _cmux_*() — private functions: _cmux_new, _cmux_start, _cmux_cd, _cmux_ls, _cmux_merge, _cmux_rm, _cmux_rm_all, _cmux_init
  • Helper functions: _cmux_repo_root, _cmux_safe_name, _cmux_worktree_dir, _cmux_spinner_start/stop

Key design patterns:

  • Idempotent operations (e.g. cmux new reuses existing worktrees)
  • Context-aware: cmux rm and cmux merge with no args detect the current worktree from $PWD
  • Branch name sanitization: feature/foofeature-foo for directory names
  • Worktrees live under .worktrees/<safe-branch-name>/ in the repo root

Setup hook system: .cmux/setup is an executable bash script that runs after worktree creation. It handles project-specific init (symlink secrets, install deps, codegen). cmux init uses Claude CLI (claude -p) to auto-generate this hook.

Key files

  • cmux.sh — the entire application
  • install.sh — curl-pipe installer that downloads cmux.sh to ~/.cmux/ and adds source line to shell RC
  • .cmux/setup — project-specific worktree setup hook (committed to repo)
  • examples/setup-node — example setup hook for Node.js projects

Shell conventions

  • 2-space indentation
  • Functions prefixed _cmux_ for internal, cmux for public
  • Zsh compatibility: uses setopt localoptions nomonitor where needed for job control
  • Error handling: validate inputs, check command -v, guard with || return 1
  • No set -e in cmux.sh (it's sourced, not executed); install.sh uses set -e

Read the full file on GitHub · 50 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. 5d ago First seen · 50 lines · 673 tokens per session scan A 796eb0e0f181

Subscribe to this mod's changes

cmux CLAUDE.md is an instructions file published in the GitHub repository craigsc/cmux (603 stars, last pushed 2mo ago), licensed MIT. It adds 673 tokens to every session, about $0.0034 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

Related

Other instructions, from other repositories