The Ralph Loop

Mon, 01 Jan 0001 00:00:00 +0000

What the Ralph loop is#

The Ralph loop is a shell loop that feeds one prompt file to a coding agent, waits for the agent to exit, and feeds it the same file again, indefinitely. Geoffrey Huntley published it on 14 July 2025, named it after Ralph Wiggum of The Simpsons, and gave its purest form as one line of Bash:

`1`	`while :; do cat PROMPT.md \| claude-code ; done`

Each pass starts a new agent process with an empty context window. Nothing from the previous pass survives except what it left on disk: the code, the git history, and a handful of files that the prompt tells every pass to read. It is the smallest complete outer loop. The previous run ending is the trigger, the prompt is the same text every time, and all of the state lives in the repository.

Loops in Claude Code

Mon, 01 Jan 0001 00:00:00 +0000

Claude Code has seven ways to send Claude its next message without a person typing it. Each is an outer loop: something outside the agent that starts a turn, and the seven differ on three questions. What starts the next turn? Where does the run happen? What has to be open while it runs?

Mechanism	Next turn starts when	Runs on	Needs an open session	Permission prompts
`/loop`	an interval elapses, or a delay Claude picked	your machine	yes	as the session
`/goal`	a turn ends and an evaluator rules the condition unmet	your machine	yes, or one non-interactive run	as the session
Stop hook	Claude ends a turn and a script blocks it	wherever the session runs	yes	as the session
Desktop scheduled task	a schedule fires	your machine	no, but the app must be open	set per task
Routine	a schedule, an HTTP call, or a GitHub event	Anthropic’s cloud	no	never asks; runs everything it can reach
`claude -p` (one prompt, one run, then exit)	the calling program runs it	wherever it is called	no	set by flags
GitHub Action	a workflow event or schedule	GitHub’s runners	no	set by `--allowedTools`

The first three keep one session going, so every iteration shares a context window with the ones before it. The other four start a new session for each run, so a run sees only what an earlier one wrote down. That split is the fresh-context question on the parent page. A same-session loop left running for days accumulates history until compaction summarizes its early iterations away; a fresh-session loop forgets everything it did not write to disk.

Loop Engineering on Bitsy Wiki

The Ralph Loop

What the Ralph loop is#

Loops in Claude Code