Re-run a stored sim_prompt against the SAME parent it originally ran against — a sibling attempt, never a chain: it never derives from the previous attempt's output, only from the original parent, so rerolling ten times leaves ten independent siblings in lineage rather than a chain of ten. Reuses the original prompt's text and system unless you override them here; a prompt with no requestTemplate (stored before sim_prompt said a stored prompt is readable by anyone with its id) has them withheld from every read, so only its author (its lineage's wasAttributedTo) may reroll it reusing them, and anyone else passes text, and system when it has one, of their own. The parent rides along as sim_prompt sends it, withheld fields left out unless you are its author. The original prompt and its result are left untouched; this stores a new prompt and a new result (model or artifact, same rule as sim_prompt) under Activity sim_reroll, and returns the same fields sim_prompt does: a model's warnings, an artifact's content inline, and modelErrors when the reply was model JSON that failed. When called with neither override and the deployment's LLM provider and model are unchanged since the original ran, the response carries a reproducibility field. If the request template (the instruction and settings sim_prompt sends; a prompt's requestTemplate) is unchanged too, it is checked against every prior result this exact prompt has ever produced (via the same forward "produced" relation sim_edges/sim_neighbors can query directly): "verified" if this result content-matches one of them, "diverged" if it doesn't, "not verified" if there's no prior result on record yet. If the template changed since the original ran, it is "not comparable", and the run is stored under a new promptId. Needs sign-in (opens OAuth the first time). Refused if this deployment has no LLM provider configured. The new prompt is readable as sim_prompt's is: without sign-in, by anyone with its id or a result's.