MemArena: An Ego-Centric Benchmark for On-Device Agentic Personal Memory Assistants at Scale

AuthorsJiadong Zhang, Xiaosong Ma

arXiv 20262026

TL;DR

MEMARENA uses the MASIM multi-agent simulator and ego-centric evidence projection to show that MemSearch beats Memobase by +32.5 pp recall on MEMARENA-L while adding only 48 ms latency.

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THE PROBLEM

Personal agents lack ego-centric dense memory at scale

Existing long-context benchmarks provide only around 0.3K tokens per speaker per dated session or undefined daily rates, far below the ∼10K human baseline.

This under-tests ego-centric, globally coherent, and activity-dense personal memory, so on-device assistants cannot be evaluated for long-horizon recall, reasoning, and permission-aware disclosure.

HOW IT WORKS

MEMARENA and MASIM world-grounded simulation

MEMARENA builds on MASIM world simulation, PP sessions, PA sessions, ego-centric projection, and benchmark question generation to generate dense, provenance-tracked personal histories.

Think of MASIM as a shared social "disk" of events and dialogs, while ego-centric projection is each agent’s private "RAM" view filtered by visibility and participation.

This design lets MEMARENA test recall, reasoning, abstention, and permission-aware access over millions of tokens in ways a plain context window or omniscient transcript cannot.

DIAGRAM

Ego-centric evidence and task generation flow

This diagram shows how MEMARENA uses MASIM to generate PP and PA dialogs, project ego-centric views, and derive evaluation instances across six dimensions.

DIAGRAM

MEMARENA evaluation and backend comparison pipeline

This diagram shows how MEMARENA-L pairs readers with memory backends, runs queries, and scores accuracy and latency.

PROCESS

How MEMARENA Handles a Personal Memory Evaluation Instance

  1. 01

    MASIM world simulation

    MASIM world simulation creates persona-driven agents, Dunbar-layered social ties, and events that feed PP sessions and PA sessions for MEMARENA.

  2. 02

    Dense PP and PA session generation

    PP sessions and PA sessions generate around 24.1K ego-observed tokens per agent per day, with provenance and access metadata logged in the shared state.

  3. 03

    Ego-centric projection and benchmark question generation

    Ego-centric projection filters the shared log to each agent’s visible evidence, and benchmark question generation builds D1–D6 tasks from this view.

  4. 04

    Reader and memory backend evaluation

    MEMARENA pairs open-weight readers with Vanilla, BM25-RAG, Oracle retrieval, Memobase, and MemSearch, then scores recall, reasoning, abstention, and permission-aware access.

KEY CONTRIBUTIONS

Key Contributions

  • 01

    MEMARENA ego-centric benchmark design

    MEMARENA introduces the first ego-centric, globally coherent, activity-dense conversational memory benchmark with 50 agents over 15 days and 10.3M dialog-text tokens.

  • 02

    MASIM multi-agent simulator

    MASIM world simulation generates PP sessions and PA sessions with day-batched synchronization, producing around 24.1K text-only ego-observed tokens per agent per day.

  • 03

    Systematic evaluation of memory backends

    MEMARENA evaluates Vanilla, BM25-RAG, Oracle retrieval, Memobase, and MemSearch with five readers, revealing MemSearch’s +32.5 pp recall and +19.2 pp reasoning gains over Memobase at Qwen3-0.6B.

RESULTS

By the Numbers

Recall Qwen3 0.6B MemSearch

56.2%

+32.5 pp over Memobase at 23.7%

Reasoning Qwen3 0.6B MemSearch

41.4%

+19.2 pp over Memobase at 22.2%

Avg accuracy Qwen3 0.6B MemSearch

36.1%

+2.9 pp over Vanilla at 33.2%

MemSearch latency overhead

48 ms

fixed TTFT add on Spark GB10 compared to 0 ms for Vanilla

MEMARENA-L is a 15-day, 50-agent benchmark testing Recall, Reasoning, and Trustworthiness for ego-centric personal memory assistants. The main result shows that MemSearch, within MEMARENA, improves content accuracy far more than scaling Qwen3 from 0.6B to 32B, while adding only modest latency.

BENCHMARK

By the Numbers

MEMARENA-L is a 15-day, 50-agent benchmark testing Recall, Reasoning, and Trustworthiness for ego-centric personal memory assistants. The main result shows that MemSearch, within MEMARENA, improves content accuracy far more than scaling Qwen3 from 0.6B to 32B, while adding only modest latency.

BENCHMARK

MEMARENA-L main grid: Qwen3-0.6B accuracy vs memory backends

Avg accuracy (%) on MEMARENA-L across six dimensions for Qwen3-0.6B with different memory backends.

KEY INSIGHT

The Counterintuitive Finding

Within MEMARENA, switching from Memobase to MemSearch at Qwen3-0.6B boosts Recall by +32.5 pp and Reasoning by +19.2 pp, dwarfing reader scaling gains.

This is surprising because many assume larger readers matter most, yet MEMARENA shows memory-backend choice dominates content accuracy while adding only 48 ms search latency.

WHY IT MATTERS

What this unlocks for the field

MEMARENA gives the community a realistic, ego-centric, activity-dense benchmark to stress-test personal memory assistants under on-device constraints and permission-aware access.

Builders can now compare memory backends like MemSearch and Memobase on long-horizon recall, reasoning, abstention, and disclosure, instead of relying on context-window size or synthetic single-task transcripts.

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