Loop until

The cycle primitive: repeatedly run the steps wired to its loop port, feeding each pass's output back in, until the stop condition over that output becomes true — then the final payload leaves the done port. This is retry-until-success, poll-until-ready, generate-and-refine.

Config

The stop condition plus the safety cap.

• Stop when — an expression over the body's output (same dialect as if): payload["status"] == "done". Checked after each pass — the body always runs at least once (do-until).
• Max iterations — safety cap, default 50, ceiling 1000. If the condition never turns true, the loop stops and the payload carries "_loop_exhausted": true.

Output

The final body output, on done. Branch on payload["_loop_exhausted"] when hitting the cap means something different than finishing.

Patterns

• Poll until ready — call a job-status API → wait → loop until status == "complete".
• Refine — generate with an AI step → validate → loop until the check passes.

Gotchas

• The condition reads the body's output, not the original input — make sure the last body step actually emits the field you're checking.
• Put a wait inside polling bodies; a tight loop against an API burns the iteration cap in seconds.