PERMA: Benchmarking Personalized Memory Agents via Event-Driven Preference and Realistic Task Environments

AuthorsShuochen Liu, Junyi Zhu, Long Shu et al.

2026

TL;DR

PERMA uses an event-driven persona state with Clean, Noise, and style-aligned long-context variants to expose where memory agents fail to maintain coherent personalization over 1.8M-token interaction histories.

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THE PROBLEM

Personalized agents collapse into needle in a haystack retrieval

Existing personalization benchmarks interleave sparse preference snippets with irrelevant dialogue, reducing evaluation to needle in a haystack retrieval.

Under these settings, agents treat preferences as static facts, ignore event-driven evolution, and fail to maintain a coherent persona state across domains and sessions.

HOW IT WORKS

PERMA: Event-driven persona states over realistic noisy interactions

PERMA builds a timeline of Interaction Events, maintains a dynamic Persona State, and evaluates dual-process Memory Systems under Clean, Noise, and style-aligned long-context settings.

You can think of PERMA as a long-term user diary plus an indexed card catalog, where events are diary pages and persona states are curated summary cards.

This event-driven construction lets PERMA probe evolving preferences and cross-domain synthesis in ways a plain context window or static RAG corpus cannot.

DIAGRAM

Event-driven interaction and task checkpoints

This diagram shows how PERMA sequences Emergence and Supplement events and inserts Type 1, Type 2, and Type 3 tasks along the interaction timeline.

DIAGRAM

PERMA evaluation pipeline across Clean, Noise, and style-aligned contexts

This diagram shows how PERMA constructs datasets, injects noise, and runs MCQ plus interactive evaluations with memory systems and standalone LLMs.

PROCESS

How PERMA Handles an Interaction Event Sequence

  1. 01

    Timeline generation

    PERMA uses a timeline generation agent (fplan) to turn domain summaries into ordered Interaction Events with Emergence, Supplement, and Task types plus dependencies.

  2. 02

    Dialogue generation

    PERMA prompts a dialogue generation agent Pg to expand each event into multi-turn dialogues and extract explicit or implicit preferences Φt into the evolving Persona State.

  3. 03

    Noise injection

    PERMA injects text variability using five in-session noise types and aligns user queries with WildChat idiolects to stress Memory Systems under realistic prompt biases.

  4. 04

    Task insertion and evaluation

    PERMA inserts Type 1, Type 2, and Type 3 tasks, then runs MCQ and interactive evaluation to test how well agents use the Persona State across temporal depth and domains.

KEY CONTRIBUTIONS

Key Contributions

  • 01

    Event-driven persona state benchmark

    PERMA builds 808 events, 3.5k Clean dialogs, and 324k Clean tokens across 10 users and 20 domains, modeling evolving preferences via Interaction Events and a dynamic Persona State.

  • 02

    Realistic noise and style alignment

    PERMA injects five prompt bias noise types and aligns queries with WildChat idiolects, creating Clean, In-session Noise, and Style-aligned Long-context datasets totaling 1,165.4k tokens.

  • 03

    Decoupled memory evaluation protocol

    PERMA separately scores retrieval (BERT-f1, Memory Score) and generation (MCQ, Completion), revealing how Memory Systems like MemOS trade token compression for persona consistency.

RESULTS

By the Numbers

MCQ Acc. (Clean single, MemOS)

0.811

+0.109 over RAG (0.702)

Memory Score (Clean single, MemOS)

2.27

+0.38 over Mem0 (1.89)

Context Token (Clean single, MemOS)

709.1 tokens

vs 34,078.6 tokens for standalone LLMs

Completion (Clean single, EverMemOS)

0.846

+0.016 over MemOS (0.830) with 3,230.5ms search duration

PERMA’s Clean single-domain benchmark tests task completion, preference consistency, and informational confidence under multi-session personalization. These results show that MemOS, evaluated within PERMA, can compress long histories while improving MCQ accuracy and Memory Score compared to vanilla RAG and raw-context standalone LLMs.

BENCHMARK

By the Numbers

PERMA’s Clean single-domain benchmark tests task completion, preference consistency, and informational confidence under multi-session personalization. These results show that MemOS, evaluated within PERMA, can compress long histories while improving MCQ accuracy and Memory Score compared to vanilla RAG and raw-context standalone LLMs.

BENCHMARK

Clean Single-Domain MCQ Accuracy for Memory Systems

MCQ Acc. on PERMA Clean single-domain tasks for GPT-4o-mini-based memory agents.

KEY INSIGHT

The Counterintuitive Finding

Under Noise, MemOS increases MCQ Acc. from 0.811 to 0.853 by retrieving more tokens (709.1 to 1,486.7), despite added in-session ambiguity.

This is surprising because we usually expect noisy prompts and longer retrieved contexts to hurt accuracy, not improve persona-state synthesis over multi-session histories.

WHY IT MATTERS

What this unlocks for the field

PERMA unlocks a way to stress-test memory agents on evolving, cross-domain persona states instead of static preference recall in toy dialogues.

Builders can now design and tune Memory Systems that explicitly manage persona drift, noise robustness, and long-context efficiency, using PERMA’s event-driven benchmarks as a realistic target.

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