Per-arm knobs that sit OUTSIDE the runner's own config object: they select which model answers and which prompt text it answers with, rather than tuning the run. Kept separate because both runners accept them while their configs share nothing.
Optional
Model + temperature for every model call in the arm. Unset → each prompt's own resolved model.
Which prompt text the arm resolves — a promotion tag, or committed snapshots only.
Per-arm knobs that sit OUTSIDE the runner's own config object: they select which model answers and which prompt text it answers with, rather than tuning the run. Kept separate because both runners accept them while their configs share nothing.