A Tiny Comparator That Never Solves the Task Improves Agent Performance in All Nine Tested Settings

arXiv 2608.21027·medium signalXBlueskyLinkedInCopy link

Don't Solve, Just Compare (arXiv 2608.21027, Aug 21) replaces the expensive expert solver or task-capable critic used for runtime intervention with COTA, a comparator that only judges whether a sampled alternative leads to a better continuation than the actor's proposal. Repeated comparisons decide when to intervene, and preferred alternatives are returned as non-binding advice so the original actor replans. Trained on pairwise supervision from same-prefix counterfactual branches, COTA improved all nine evaluation settings across WebShop, ALFWorld and tau^3-Retail with three actors, showing constructive intervention works even when the auxiliary model is substantially weaker at solving the task than the actor.