arXiv Machine Learning By Ehsan Saleh, Roozbeh Nahavandi, Sama Salarian, Raef Bassily, Andrew Perrault

AfterDeleteBench: Auditing Post-Deletion Information Persistence in LLM Agents

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AfterDeleteBench is a controlled behavioral audit designed to test whether large language model agents retain information after a memory record is deleted. The benchmark compares agents that have been exposed to a synthetic secret and then had the original memory removed against matched agents that never saw the secret, attributing any post‑deletion recovery to the initial exposure. Results show that a single query can recover deleted secrets from models such as Qwen2.5‑7B‑Instruct in about two thirds of cases, and that reconstruction can succeed even when the full secret string is absent, with success rates of 62‑99% across Qwen, Mistral, and Phi‑3.

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