MemSyco-Bench: Benchmarking Sycophancy in Agent Memory
arXiv · HuggingFace · ▲24
Abstract (verbatim)
Memory has emerged as a cornerstone of modern LLM-based agents, supporting their evolution from single-turn assistants to long-term collaborators. However, memory is not always beneficial: retrieved memories often induce a critical issue of sycophancy, causing agents to over-align with the user at the cost of factual accuracy or objective reasoning. Despite this emerging risk, existing memory benchmarks primarily evaluate whether memories are correctly stored, retrieved, or updated, while overlooking how retrieved memories influence downstream reasoning and decision-making. To bridge this gap, we propose MemSyco-Bench, a comprehensive benchmark for evaluating memory-induced sycophancy in agent systems. MemSyco-Bench measures when memory should influence a decision and how valid memory should be used. Specifically, it covers five tasks that assess whether agents can reject memory as factual evidence, respect its applicable scope, resolve conflicts between memory and objective evidence, track memory updates, and use valid memory for personalization. All related resources are collected for the community at https://github.com/XMUDeepLIT/MemSyco-Bench.
Background
Background Analysis
Technical Context: Modern LLM-based agents are evolving from single-turn assistants to long-term collaborators (e.g., personal assistants, educational or customer service systems) that need to retain user preferences, historical decisions, and task experiences to provide personalized and coherent services. For instance, remembering a user’s coffee preference or maintaining consistent medical advice across consultations. However, memory is not always beneficial—when historical information is outdated, out of context, or conflicts with objective facts, agents may blindly rely on old memories, leading to factually incorrect or irrational responses.
Previous Limitations: Existing memory benchmarks (e.g., LongMemEval, PersonaMem) focus on whether agents can correctly store, retrieve, and use memories but ignore a critical question: when to trust memory and when to question or ignore it. For example, if a user previously held a wrong belief that "the Great Wall is visible from space with the naked eye," an agent might cite this incorrect memory instead of current scientific evidence. Moreover, traditional benchmarks do not distinguish whether memory use is justified (e.g., whether to reject memory interference when objective evidence exists), making their evaluations irrelevant to real-world reliability.
Our Solution: MemSyco-Bench addresses this by designing five tasks to test how agents handle memory-induced sycophancy. These tasks include:
1. Rejecting invalid memory: Can the agent ignore memory when it conflicts with facts?
2. Respecting scope: Is memory only valid in specific contexts (e.g., a user’s past preference may not apply to new situations)?
3. Resolving conflicts: Can the agent prioritize objective evidence over conflicting memory?
4. Updating memory: Can the agent identify and correct outdated memories?
5. Appropriate personalization: Can the agent use memory to enhance service when appropriate (e.g., recommending a previously liked restaurant)?
Key Difference: Unlike prior work, MemSyco-Bench does not evaluate "whether memory is correctly retrieved" but focuses on "how to use retrieved memory reasonably." It defines "memory-induced sycophancy" as a distinct failure mode and quantifies an agent’s ability to balance personalization and factual accuracy through concrete scenarios. This perspective fills gaps in existing benchmarks and provides a critical tool for developing reliable long-term memory agents.




