Entity-Collision: A Stratified Protocol for Attributing Retrieval Lift in Agent Memory

End-to-end agent-memory benchmarks report a single hit@k per retriever, confounding lexical leakage (uncontrolled query/gold/distractor entity overlap) with tag-mixing (preferences, services, tools averaged together). We propose entity-collision, a system-agnostic protocol that pins the BM25 floor by construction -- every distractor shares the answer's entity tokens -- and stratifies queries by discriminator tag, so any lift over BM25 is attributable to the embedder. Applied to an open-source ag

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ethics.ai (28 May 2026), “Entity-Collision: A Stratified Protocol for Attributing Retrieval Lift in Agent Memory,” evidence record 3519, https://ethics.ai/record/3519 (originally published by arXiv).

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