Replay

Replay re-runs a recorded attempt, optionally on a different runtime or model, feeding it the exact original prompt. It's how you check what a different model would have done with the same task, without rebuilding anything or hand-copying prompts.

How replay works

When you replay an attempt, Ringmaster takes the compiled prompt that attempt was sent (the one with its inputs already baked in) and feeds it, unchanged, to the target you choose. The new run is recorded as a fresh attempt that notes it was a replay of the original, so the lineage is never lost. The source attempt stays exactly as it was.

Overrides

You can keep everything the same and just re-run, or change the target:

• Runtime: replay the attempt on a different runtime.
• Model: replay on a different model (with a compatible runtime).
• Slot: for a multi-agent attempt, scope the replay to a single slot rather than the whole attempt.

A common use is to take a result a local model produced and replay it on a frontier model to see if the extra capability changes the answer, or the reverse, to check whether a cheaper or local model is good enough.

Staying local

If you want to be sure a replay won't reach for a paid provider, force it to stay local. A replay constrained this way keeps a local source attempt local and refuses to escalate to a hosted runtime. It's the safe default for experimenting at no cost, and it's how the CLI behaves when you pass --local-only.

From the app

Open the attempt you want to replay and choose Replay from its context menu. Pick a runtime and model if you want to change them, or accept the originals, and run. The result lands as a new attempt you can compare against the source.

From the command line

Replay is also a CLI command, which makes it easy to script "run this past attempt on three different models and compare":

ringmaster replay .ring/runs/<run-id> --stage draft --attempt 1 \
  --runtime gemini-api --model gemini-2.5-pro

--stage and --attempt are required; add --slot for a specific slot, --runtime/--model to retarget, or --local-only to stay offline. Full flags are in The ringmaster CLI.

Provenance

Because replay preserves the original inputs and records the link back to the source attempt, the resulting artifact's provenance tells the whole story: what it was replayed from, what changed (the new runtime or model), and everything that's true of any attempt. Replays are comparable to their sources exactly like any two attempts; see Provenance, reports & metrics.