ActiveMem: Distributed Active Memory for Long-Horizon LLM Reasoning

AuthorsYunhan Jiang, Wenbin Duan, Shasha Guo et al.

arXiv 20262026

TL;DR

ActiveMem uses a decoupled Planner plus Distributed Memory System to store query-conditioned gists and reaches 0.79 LasJ on BrowseComp-Plus with only 2145 PFLOPs.

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THE PROBLEM

Centralized agents trade trajectory length for memory fidelity

ActiveMem targets centralized memory systems where context compression causes permanent information loss, leaving memory content irreversibly degraded and unrecoverable for later reasoning.

In long-horizon web reasoning like BrowseComp-Plus and GAIA, this forces agents to choose between context overload and losing evidence, degrading downstream LasJ accuracy as trajectories grow.

HOW IT WORKS

ActiveMem — Decoupled Planner and Distributed Memory System

ActiveMem’s core mechanism separates a high-level Planner from a Distributed Memory System composed of Memorizers, Memory Shards, and an Operator that manage query-conditioned gists.

Like a prefrontal cortex issuing control signals to a hippocampus, the Planner sends focused queries while Memorizers and Memory Shards act as distributed long-term storage.

This decoupling lets ActiveMem keep the Planner’s context clean and compact while preserving document-level information in shards, avoiding the centralized trade-off between context length and memory fidelity.

DIAGRAM

ActiveMem Inference Flow Between Planner and Memory System

This diagram shows how ActiveMem routes Planner queries through the Operator and Memorizers to Memory Shards and back as distilled gists at inference time.

DIAGRAM

ActiveMem Evaluation and Ablation Design

This diagram shows how ActiveMem is evaluated on BrowseComp-Plus and GAIA and how ablations on Memory Shards and Memorizer variants are organized.

PROCESS

How ActiveMem Handles a Long-Horizon Web Task

  1. 01

    Planner

    The Planner maintains state s_t = (x, h_t, m_{t-1}), trims history to the most recent K steps, and emits retrieval queries Q_t.

  2. 02

    Distributed Memory System

    The Distributed Memory System receives retrieved documents D_t, routes them to Memory Shards, and orchestrates Memorizers and the Operator for gist distillation.

  3. 03

    Memorizers

    Memorizers take each (q, c) pair, generate query-conditioned gists g_c = ω(c, q), and write them into the appropriate Memory Shards.

  4. 04

    Operator

    The Operator detects memory hits or misses, reuses or updates shard entries, consolidates gists asynchronously, and returns distilled gists G_t to the Planner.

KEY CONTRIBUTIONS

Key Contributions

  • 01

    Neuroscience-inspired cognitive decoupling

    ActiveMem draws on prefrontal cortex and hippocampus complementarity to separate the Planner’s executive control from distributed memory consolidation in Memorizers and Memory Shards.

  • 02

    The ActiveMem framework

    ActiveMem introduces a Distributed Memory System where parallel Memorizers distill gists, Memory Shards persist them, and an Operator coordinates routing and consolidation.

  • 03

    Superior accuracy with lower computational cost

    On BrowseComp-Plus, ActiveMem reaches 0.79 LasJ with 2145 PFLOPs, improving MemoBrain’s 0.63 LasJ at 1640 PFLOPs by +0.16 LasJ.

RESULTS

By the Numbers

LasJ

0.79

+0.07 over Context-Folding

PFLOPs (BrowseComp-Plus)

2145

2145 vs 3920 for Context-Folding

LasJ (GAIA)

0.62

+0.03 over AgentFold and MemoBrain

PFLOPs (GAIA)

187

187 vs 516 for MemoBrain

On BrowseComp-Plus and GAIA WebSearch, which test long-horizon web reasoning, ActiveMem delivers higher LasJ accuracy at substantially lower PFLOPs than centralized memory agents and vanilla ReAct LLMs.

BENCHMARK

By the Numbers

On BrowseComp-Plus and GAIA WebSearch, which test long-horizon web reasoning, ActiveMem delivers higher LasJ accuracy at substantially lower PFLOPs than centralized memory agents and vanilla ReAct LLMs.

BENCHMARK

Overall evaluation on BrowseComp-Plus

Total LasJ score on BrowseComp-Plus across Easy, Medium, and Hard splits.

BENCHMARK

Module-level PFLOPs breakdown for ActiveMem on BrowseComp-Plus

PFLOPs per module in ActiveMem on BrowseComp-Plus.

KEY INSIGHT

The Counterintuitive Finding

ActiveMem processes 188M tokens on BrowseComp-Plus, more than centralized agents’ 47–167M, yet uses only 2145 PFLOPs and still reaches 0.79 LasJ.

This is surprising because more tokens usually imply higher cost, but ActiveMem’s small 4B Memorizers handle most tokens cheaply while the large Planner stays context-light.

WHY IT MATTERS

What this unlocks for the field

ActiveMem shows that decoupling reasoning from memory lets agents scale to long-horizon tasks while keeping a compact, high-quality reasoning context.

Builders can now design agents that aggressively read and reuse web evidence via distributed gists, without being constrained by a single monolithic context window.

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