GraphMemix: Query-Aware Evidence Forests for Long-Term Multimodal Agent Memory

AuthorsGeng Li, Yuhao Wang, Dong Li et al.

arXiv 20262026

TL;DR

GraphMemix builds a query-aware evidence forest over multimodal memories, using anchor-conditioned graph optimization to reach 61.55% Judge Accuracy (macro) vs 49.80% for UniversalRAG (+11.75pp).

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THE PROBLEM

Long-Term Multimodal Agents Waste Context and Miss Evidence

Existing question-agnostic memory systems must process the entire user history to avoid omissions, creating large cold-start and update costs and still dropping decisive visual or local context.

Similarity-based multimodal RAG overselects near-duplicate records and misses low-similarity complementary evidence, even though GraphMemix’s benchmarks show many answers require multiple memories whose joint utility is not captured by similarity alone.

HOW IT WORKS

GraphMemix: Query-Conditioned Evidence Forests

GraphMemix centers on three components: candidate graph construction, evidence utility and activation costs, and forest optimization, turning multimodal memories into a query-aware evidence forest.

You can think of GraphMemix as a smart card catalog plus wiring: it first finds relevant cards, then checks which cards truly help together, and finally wires them into trusted trees under a context budget.

This anchor-conditioned forest optimization lets GraphMemix recover low-similarity but necessary evidence and suppress redundant or conflicting memories, something a plain context window or top-K similarity ranking cannot do.

DIAGRAM

Query-Time Evidence Retrieval Pipeline

This diagram shows how GraphMemix processes a single question: from multi-view seed retrieval through graph expansion, verification, and forest selection.

DIAGRAM

Evaluation Benchmarks and Lifecycle Cost Pipeline

This diagram shows how GraphMemix is evaluated across four multimodal memory benchmarks, including lifecycle cost measurement and judge-based accuracy.

PROCESS

How GraphMemix Handles a Long-Term Multimodal Question

  1. 01

    Candidate Graph Construction

    GraphMemix runs multi-view retrieval over text, images, video, and OCR, then expands top-L seeds via schema and mutual KNN edges into a bounded candidate subgraph C_q.

  2. 02

    Evidence Utility and Activation Costs

    GraphMemix uses a listwise node verifier to compute p_i(q) and an Evidence-Chain Verifier to assign incremental-support scores, roles, and edge costs c_e(q) for anchor-conditioned schema relations.

  3. 03

    Forest Optimization

    GraphMemix maximizes node utility minus edge uncertainty and component cost, using a two-stage solver with 1-swap local search and exact maximum-weight forest computation via Kruskal’s algorithm.

  4. 04

    Evidence Forest Serialization

    GraphMemix orders components by root utility, traverses each tree breadth-first, and serializes at most K multimodal memories into O_q for the frozen LVLM reader to answer the question.

KEY CONTRIBUTIONS

Key Contributions

  • 01

    Query-Conditioned Evidence Forest Formulation

    GraphMemix formulates long-term multimodal memory selection as a forest optimization objective Unode(S|q) − Cedge(F|q) − Copen(S,F), enabling adaptive cardinality and structured evidence sets under a reader budget K.

  • 02

    Anchor-Conditioned Evidence-Chain Verifier

    GraphMemix introduces an Evidence-Chain Verifier that assigns roles like new_fact, clarification, redundant, and conflict, and computes incremental-support scores s_inc_ai(q) to gate schema edges and suppress unreliable expansion.

  • 03

    Lifecycle-Cost Pareto Frontier on Multimodal Benchmarks

    GraphMemix achieves 61.55% macro Judge Accuracy with Qwen3-VL and 67.42% with Gemma 4 on ATM, Mem-Gallery, MemEye, and H2HMem, while shortening ATM-Bench’s full lifecycle by up to 4.74× compared to LightMem.

RESULTS

By the Numbers

Judge Accuracy macro (Qwen3-VL)

61.55%

+11.75pp over UniversalRAG (49.80%)

ATM Judge Accuracy (Qwen3-VL)

55.27%

+6.80pp over MemGuide (48.47%)

Mem-Gallery Judge Accuracy (Qwen3-VL)

76.33%

+12.57pp over UniversalRAG (63.76%)

H2HMem Judge Accuracy (Gemma 4)

63.47%

+15.14pp over UniversalRAG (48.34%)

On ATM-Bench, Mem-Gallery, MemEye, and H2HMem, GraphMemix is evaluated with Qwen3-VL-8B-Instruct and Gemma 4 12B Unified using GPT-5-mini as judge. These numbers show GraphMemix’s query-local graph organization consistently improves answer correctness over strong multimodal baselines like UniversalRAG and MemGuide.

BENCHMARK

By the Numbers

On ATM-Bench, Mem-Gallery, MemEye, and H2HMem, GraphMemix is evaluated with Qwen3-VL-8B-Instruct and Gemma 4 12B Unified using GPT-5-mini as judge. These numbers show GraphMemix’s query-local graph organization consistently improves answer correctness over strong multimodal baselines like UniversalRAG and MemGuide.

BENCHMARK

Judge Accuracy on Four Multimodal Memory Benchmarks (Qwen3-VL-8B-Instruct)

Judge Accuracy (%) for GraphMemix versus key baselines on ATM, Mem-Gallery, MemEye, and H2HMem (macro-average).

BENCHMARK

Judge Accuracy on Four Multimodal Memory Benchmarks (Gemma 4 12B Unified)

Judge Accuracy (%) for GraphMemix versus key baselines on ATM, Mem-Gallery, MemEye, and H2HMem (macro-average).

KEY INSIGHT

The Counterintuitive Finding

GraphMemix’s bounded candidate graph reveals that 37.87% of Mem-Gallery’s gold evidence is recoverable only via relational expansion, not direct top-10 similarity.

This is counterintuitive because many retrieval pipelines assume high-similarity memories suffice, yet GraphMemix shows crucial evidence often lives in low-similarity neighbors reachable only through schema and anchor-conditioned edges.

WHY IT MATTERS

What this unlocks for the field

GraphMemix unlocks query-time reconstruction of a structured evidence forest, letting agents reason over long multimodal histories without expensive global summarization.

Builders can now design memory systems that recover complementary, low-similarity evidence and maintain trusted relational context, enabling more reliable long-horizon personal assistants and multimodal RAG agents.

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