Ralph Wiggum — Anthropic Official Autonomous Loop Plugin

How Ralph Wiggum Works

A Ralph loop is structurally a while true that re-runs Claude Code with the same prompt file each iteration, accumulating context and self-correcting until either:

1. The model emits an explicit completion sentinel (the --completion-promise string), OR
2. --max-iterations is reached.

Boris Cherny on his personal setup page (howborisusesclaudecode.com): "For very long running tasks, I either prompt Claude to verify its work with a background agent, use an agent-stop hook, or use the Ralph Wiggin plugin for autonomous looping."

Slash commands installed

When to reach for it

• Multi-file refactors that need many edit-test cycles
• TDD: "make all tests pass, then output COMPLETE"
• Long migrations (e.g. "convert all class components to hooks")
• Avoid for open-ended exploration (Ralph keeps going — burns tokens)
• Avoid when verification is hard to express as a single sentinel string

Cost discipline (must-read)

Ralph will happily burn through your token budget. Boris's safety pattern:

1. Always set --max-iterations (never default unlimited).
2. Make --completion-promise something Claude can only emit when all tests pass.
3. Start with small tasks; observe iteration count before scaling.

Example: full TDD loop

/ralph-loop "
Implement a TypeScript function 'parseDuration(input: string): number' that
parses strings like '2h30m', '1d', '45s' into milliseconds.

Requirements:
1. Run npm test after each iteration
2. Fix all failing tests
3. When all tests pass AND npm run lint is clean, output:
   <promise>RALPH_COMPLETE</promise>
" --completion-promise "RALPH_COMPLETE" --max-iterations 30

FAQ

Q: What is Ralph Wiggum for Claude Code? A: An official Anthropic-maintained Claude Code plugin that adds /ralph-loop and /cancel-ralph slash commands, letting Claude run an autonomous self-improving loop until it hits a completion sentinel or max-iterations cap.

Q: Is Ralph Wiggum free? A: Yes, the plugin itself is free and open source under Anthropic's claude-plugins-official marketplace. You only pay for the Claude API tokens consumed during the loop.

Q: How do I install Ralph Wiggum? A: Run /plugins install ralph-wiggum inside any Claude Code session. No additional config or marketplace registration needed.

Q: How do I stop a runaway loop? A: Use /cancel-ralph from inside the same session, or set --max-iterations upfront so the loop self-terminates.

Q: Can I use Ralph for non-coding tasks? A: Yes — community variants like ralph-wiggum-marketer use the same loop pattern for copy iteration. The official plugin is task-agnostic; success depends on writing a verifiable completion-promise.