MEMO: Multimodal Evidence Memory Organization for Long-Horizon LLM Agents

AuthorsXian Gao, Jinpeng Wang, Jiacheng Ruan et al.

arXiv 20262026

TL;DR

MEMO uses query-conditioned evidence units plus a trained memory manager to mix text and visual layouts, reaching 73.91 F1 on 2Wiki under a 128-token budget.

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THE PROBLEM

Long-horizon agents waste context on redundant memory (128-token budget bottleneck)

LLM agents accumulate long interaction histories, but a fixed context budget forces important and irrelevant content to compete at nearly uniform token cost.

On multi-hop QA benchmarks like 2WikiMultiHopQA, purely textual or purely visual memory under a 128-token budget yields only 56.26 and 35.89 F1, hurting downstream reasoning.

HOW IT WORKS

MEMO — Multimodal Evidence Memory Organization

MEMO’s core mechanism chains a query-conditioned evidence extractor, deterministic unit-materialization, a trained memory manager, and working memory building into a single readout pipeline.

You can think of MEMO like a librarian that clips key passages into cards, then decides whether to file each card as text, lay it out visually, or keep both, under a shared shelf budget.

This evidence-level multimodal organization lets MEMO preserve precise facts as text while using visual layouts for structure, something a plain context window of text tokens alone cannot achieve.

DIAGRAM

Query-time Working Memory Construction Flow

This diagram shows how MEMO processes a query to extract evidence units, assign modalities, and build a text plus visual working memory under a shared budget.

DIAGRAM

MEMO Training and Evaluation Pipeline

This diagram shows how MEMO trains the evidence extractor and memory manager using benchmark evidence and frozen reader feedback, then evaluates on downstream tasks.

PROCESS

How MEMO Handles a Query-specific Working Memory Construction

  1. 01

    Query-Conditioned Evidence Extraction

    MEMO uses the query-conditioned evidence extractor to select source identifiers and character-level spans from memory records, producing compact evidence candidates tailored to the query.

  2. 02

    Unit-Materialization Step

    MEMO deterministically copies content around each span, forming evidence units with fields like id, content xi, key spans hi, source si, and priority rule ci.

  3. 03

    Joint Evidence Selection and Presentation

    MEMO’s memory manager assigns each evidence unit an action from text, image, dual, or drop, and chooses visual templates such as cards, timelines, tables, or checklists under a shared budget.

  4. 04

    Working Memory Building

    MEMO’s working memory building module assembles a text packet T and visual page V from the planned units, verifies Ctext plus Cvis within budget B, and feeds this working memory to the frozen reader.

KEY CONTRIBUTIONS

Key Contributions

  • 01

    Query-conditioned working memory construction

    MEMO formulates memory readout as building query-specific working memory under a shared budget, integrating query-conditioned evidence extraction, memory manager decisions, and working memory building into one optimization framework.

  • 02

    Multimodal evidence units

    MEMO introduces traceable evidence units with source links, key spans, and priority rules, enabling the memory manager to assign text, image, dual, or drop actions while preserving critical semantics.

  • 03

    Systematic multimodal evaluation

    MEMO is evaluated on HotpotQA, 2WikiMultiHopQA, LoCoMo, and ALFWorld with readers like Qwen3-VL-32B, achieving 73.91 F1 on 2Wiki under a 128-token budget and using only 83.93 tokens on average without truncation.

RESULTS

By the Numbers

F1

73.91%

+17.65 over Text-only on 2Wiki with Qwen3-VL-32B under 128-token budget

EM

62.20%

+5.78 over MemAgent on 2Wiki with Qwen3-VL-32B under 128-token budget

Overall F1

63.84%

+1.84 over MemAgent with Qwen3-VL-32B under 128-token budget

Tokens

83.93

50.5% fewer than MemAgent’s 169.55 tokens without truncation for InternVL3.5-8B

On 2WikiMultiHopQA, which tests multi-hop document reasoning, MEMO reaches 73.91 F1 under a 128-token budget with Qwen3-VL-32B, compared to 56.26 for Text-only and 35.89 for Visual-only memory. These results show that MEMO’s evidence-level multimodal organization yields higher answer quality while staying within strict context limits.

BENCHMARK

By the Numbers

On 2WikiMultiHopQA, which tests multi-hop document reasoning, MEMO reaches 73.91 F1 under a 128-token budget with Qwen3-VL-32B, compared to 56.26 for Text-only and 35.89 for Visual-only memory. These results show that MEMO’s evidence-level multimodal organization yields higher answer quality while staying within strict context limits.

BENCHMARK

Results under 128-token budget limitation with Qwen3-VL-32B on 2Wiki

F1 on 2WikiMultiHopQA under a 128-token memory budget with Qwen3-VL-32B as the reader.

KEY INSIGHT

The Counterintuitive Finding

MEMO uses only 83.93 tokens on average without source-memory truncation, yet still ranks first or second on every overall EM and F1 metric.

This is surprising because many systems assume more context is always better, but MEMO shows carefully organized multimodal memory can match or beat larger contexts with far fewer tokens.

WHY IT MATTERS

What this unlocks for the field

MEMO unlocks evidence-level multimodal memory planning, letting agents keep precise textual anchors while leveraging visual layouts for structure under tight budgets.

Builders can now design long-horizon agents that maintain effective working memory across thousands of steps without saturating context windows or sacrificing fine-grained semantic fidelity.

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