ArborMem: Navigating Interaction States with Memory Forests

AuthorsZongwei Lv, Yuemeng Xu, Yilun Yao et al.

arXiv 20262026

TL;DR

ArborMem uses a navigable memory forest with interaction-state localization to reach 81.00% on BranchMemEval, +5.00 points over the strongest baseline.

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THE PROBLEM

Interleaved conversations confuse agents even with full history (continuity ≠ relevance)

Existing long-term memory benchmarks show that exposing more context does not ensure reliable access, and visibility alone cannot guarantee correct evidence use.

When conversations interleave multiple tasks and plans, assistants misidentify which prior interaction state a new turn resumes, causing thread confusion, lost continuity, and incorrect answers.

HOW IT WORKS

ArborMem — Navigable Memory Forests for Interaction-State Localization

ArborMem combines a Conversation forest, Reusable evidence store, State localization, Context assembly and generation, and Online memory commit to represent resumable interaction trajectories.

You can think of ArborMem like a file system plus an index: each branch is a folder capturing one task’s history, while a separate catalog tracks reusable facts and artifacts.

This design lets ArborMem restore the right branch-local context and add cross-branch evidence, something a plain context window or flat retriever cannot achieve.

DIAGRAM

Online Interaction Flow in ArborMem

This diagram shows how ArborMem processes each user turn through state localization, branch-local context reconstruction, cross-branch retrieval, and response generation.

DIAGRAM

Evaluation and Ablation Pipeline for ArborMem

This diagram shows how ArborMem is evaluated across benchmarks, read budgets, and ablation configurations.

PROCESS

How ArborMem Handles a Long-Running Conversation Session

  1. 01

    State Localization

    ArborMem uses State localization over the Conversation forest to select a parent state p_t via hybrid retrieval and branch aware reranking.

  2. 02

    Context Assembly and Generation

    ArborMem reconstructs the branch local trajectory and augments it with evidence from the Reusable evidence store before passing E_t to the Generator LLM.

  3. 03

    Online Memory Commit

    ArborMem attaches a new node into the Conversation forest and updates the Reusable evidence store with extracted facts and structured records.

  4. 04

    Read Budget Constrained Query

    ArborMem enforces an answer time evidence budget while selecting branch local context and cross branch evidence for efficient generation.

KEY CONTRIBUTIONS

Key Contributions

  • 01

    Interaction-State Localization

    ArborMem formalizes State localization over a Conversation forest so each turn first selects which prior trajectory it resumes before retrieving evidence.

  • 02

    Navigable Memory Forest

    ArborMem represents long running conversations as a Conversation forest plus Reusable evidence store, separating interaction continuity from reusable facts and artifacts.

  • 03

    BranchMemEval Benchmark

    ArborMem introduces BranchMemEval with 33 sessions and 100 questions, showing a 5.00 point gain over the strongest baseline on branch structured memory.

RESULTS

By the Numbers

LongMemEval accuracy

68.40%

+9.00 over A-MEM

LoCoMo accuracy

53.15%

+10.31 over BM25

BEAM 100K accuracy

49.75%

+3.36 over Mem0

BranchMemEval accuracy

81.00%

+5.00 over Mem0

On LongMemEval, LoCoMo, BEAM 100K, and BranchMemEval, ArborMem is evaluated for conversational memory and branch structured reasoning. The 81.00% on BranchMemEval proves ArborMem handles interleaved, resumable trajectories better than existing memory systems.

BENCHMARK

By the Numbers

On LongMemEval, LoCoMo, BEAM 100K, and BranchMemEval, ArborMem is evaluated for conversational memory and branch structured reasoning. The 81.00% on BranchMemEval proves ArborMem handles interleaved, resumable trajectories better than existing memory systems.

BENCHMARK

Answer accuracy on BranchMemEval

Accuracy (%) on BranchMemEval across memory systems.

KEY INSIGHT

The Counterintuitive Finding

On a 50 question LongMemEval subset with a 256 token budget, ArborMem reaches 64.0% accuracy while the next best method reaches only 38.0%.

This is surprising because smaller contexts are usually expected to hurt performance, yet ArborMem’s state localization makes it stronger under the tightest read constraints.

WHY IT MATTERS

What this unlocks for the field

ArborMem unlocks reliable handling of interleaved, resumable conversational trajectories by combining interaction state localization with a navigable memory forest.

Builders can now create assistants that track multiple long running tasks and plans over weeks without conflating threads, even under strict context budgets.

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