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Retrieving the right fact was not enough for agent memory: an obsolete competing statement cut Qwen2.5 accuracy from 100 percent to 44.6 percent

AspireAI community · arXiv
Memory-agent benchmarks usually collapse retrieval and generation into one score, so it is hard to tell whether an agent failed because an update was missing or because it ignored an update it already had. On the single-hop FactConsolidation task of MemoryAgentBench, Qwen2.5-7B-Instruct accuracy falls from 45 percent to 32 percent when the retrieved evidence budget grows from 64 to 512 tokens over 6K histories, even though a gold-assisted audit finds the newest statement in every retrieved set, and the errors concentrate on questions that also carry an obsolete version. Under a frozen prompt and equal four-statement evidence size, swapping one unrelated statement for the obsolete competing statement drops accuracy from 100 percent to 44.6 percent for Qwen2.5 and from 100 percent to 87.8 percent for Qwen3-14B, with all 50 harmful paired flips classified as stale; a 32K-history replication also favours BM25-64 over BM25-512, 69 percent against 58 percent. The limit: it is one benchmark task on two open-weight models, which establishes the failure mode rather than measuring how often it happens in production memory systems.
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