Visual explainer: three probes rank base models via the decisive trajectory step

hyunw_kim · x · 2026-10-20

A visual explainer from the NVIDIA thread: replay successful agent trajectories to locate the decisive step T (the first fail→pass flip), then rank base checkpoints with three probes using real harness context (test task, trajectory prefix, environment state at T): Decisive-Action BPB (NLL of the golden action per byte, lower is better), Patch MCQ (selecting the golden action), and Prefix-conditioned pass@K (pass coverage from sampled continuations) — without ever running the base model through a full task.

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