INV-15: A Formal Safety Invariant for KV-Cache Reuse in Multi-Agent Judge Pipelines

Cross-agent KV-cache reuse delivers 7-17x compression in multi-agent LLM pipelines, but silently corrupts judge/critic agents via the Judge Candidate Reuse (JCR) failure mode. We introduce INV-15, a formal safety invariant requiring judge-class agents with JCR risk score above 0.7 to use dense prefill. Implemented as the JCR Safety Gate in ContextForge (AMD Instinct MI300X, ROCm 7.x, vLLM V1 ATOM plugin). Results: 0 INV-15 violations, critic dense prefill rate 1.000, compatible with 10.81x TokenDance compression. First production implementation of a formal safety invariant for cross-agent KV-cache reuse.