Claude Clamshell

Claude Clamshell

Prevents your Mac from sleeping while Claude Code is actively working. Close the lid and walk away - your Mac stays awake during Claude's turn and sleeps when it's waiting for your input.

Requirements

• macOS 15+ (uses the built-in caffeinate and jq commands)
• Claude Code

Installation

claude plugin marketplace add mrexodia/claude-marketplace
claude plugin install claude-clamshell@mrexodia

How it works

Four lifecycle hooks coordinate caffeinate:

Hook	What it does
SessionStart	Walks the process tree to find the Claude Code PID and caches it
UserPromptSubmit	Starts caffeinate -s -w <claude-pid> at the beginning of every turn
Stop	Kills caffeinate when Claude finishes, so your Mac can sleep between turns
StopFailure	Same cleanup when a turn ends due to an API error

The -w <claude-pid> flag is a safety net: if Claude Code crashes, is force-killed, or exits unexpectedly, caffeinate dies automatically because the watched PID no longer exists. No orphan processes, no stale PID files.

Notes

• Multiple Claude Code instances are handled via per-session PID files (/tmp/claude-clamshell-<session-id>.pid)
• The -s flag on caffeinate prevents system sleep (keeps the system awake even on AC power with the lid closed)
• Worst case on unclean exit: your Mac stays awake until the caffeinate process notices Claude's PID is gone, which is near-instant
• When Claude Code runs background processes the Stop will not kill caffeinate until after they finish