VeriMem: Serving-Time Verification for Mutable Agent Memory

Persistent memory lets language-model agents reuse information across interactions, but source updates can leave cached summaries and plans obsolete. Rejecting an entire derivative prevents stale reuse at the cost of discarding unaffected information. We introduce VeriMem, which records source invalidation and checks versioned dependencies before memory enters model input, either rejecting unsupported derivatives or reconstructing their admissible components. Under explicit lineage and serving-state assumptions, these rules provide conditional exclusion and retention properties. Lifecycle tests eliminate observed stale-derivative exposure, while reconstruction satisfies 32/32 answer contracts versus 8/32 for whole-artifact rejection on 32 inputs from 16 related worlds, matching equally informed component baselines. With Qwen3.5-9B Q4, verified contexts raise accuracy by 16.7 percentage points on 60 previously seen LongMemEval-V2 questions with injected stale content, while reconstruction yields 56 current-answer matches versus 40 for rejection across 72 related MQuAKE questions. These results support serving-time verification as a complement to eager maintenance, combining invalid-content exclusion with selective retention to improve answers in the evaluated settings.