## Computer Science > Artificial Intelligence ## Title:TwinCheck: Evidence-Grounded Negative-Twin Verification for Stateful Tool Agents > Abstract:A single locally plausible tool call can derail an otherwise successful agent trajectory. Suspicion alone does not justify intervention, because the replacement itself can introduce the very failure verification is meant to prevent. We introduce TwinCheck, an inference-time verification policy that considers replacement only when the trace satisfies an evidence condition tied to a trace-local failure hypothesis. It constructs a trace-grounded…