CMU's SSR turns agent reasoning into selection, cutting per-turn latency 90%+

CarnegieMellonU · hf · 2026-10-07

CMU released Selection-based Structured Reasoning (SSR). For small models whose free-form reasoning is long, costly, and barely guides actions, SSR reformulates reasoning as selection: recurring high-level reasoning is pre-specified as reusable natural-language candidates, and the model picks one per turn based on context likelihoods, with no auxiliary task head. Pre-specified traces enable parallel scoring via teacher-forced prefilling with a shared KV cache.

On 7 multimodal search benchmarks with 2B/4B models, SSR yields large efficiency gains across RL objectives and SFT: success rates match leading same-scale search agents while cutting per-turn reasoning latency by over 90% and total per-question latency by 28-54%.

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