AdaMEM: Test-Time Adaptive Memory for Language Agents

AuthorsYunxiang Zhang, Yiheng Li, Ali Payani, Lu Wang

arXiv 20262026

TL;DR

AdaMEM uses a hybrid long-term trajectory memory plus short-term strategy memory with STEP-MFT, reaching 58.2% unseen ALFWorld success (+6.0 over Synapse).

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THE PROBLEM

Static episode-level memory leaves agents stuck with obsolete strategies (up to 13% gap on ALFWorld)

AdaMEM targets agents that only retrieve memory once at episode start, forcing static guidance that drifts on long-horizon tasks and hurts adaptation.

On ALFWorld and WebShop, this rigidity leaves static memories up to 13% and 11% behind AdaMEM, causing agents to repeat failing behaviors instead of correcting mid-trajectory.

HOW IT WORKS

AdaMEM — Hybrid Long-Term Trajectory Memory and Short-Term Strategy Memory

AdaMEM’s core mechanism is a hybrid of Long-Term Trajectory Memory, Short-Term Strategy Memory, ADAMEM-HIGH, ADAMEM-LOW, and STEP-MFT for step-wise test-time adaptation.

You can think of Long-Term Trajectory Memory as disk storing rich past trajectories, while Short-Term Strategy Memory acts like RAM holding a compact, situation-specific plan.

This design lets AdaMEM synthesize fresh strategies conditioned on the current state, enabling continuous adaptation that a fixed context window or static prompt cannot provide.

DIAGRAM

Step-wise Inference Flow for AdaMEM-HIGH and AdaMEM-LOW

This diagram shows how AdaMEM-HIGH and AdaMEM-LOW decide when to retrieve from Long-Term Trajectory Memory and update Short-Term Strategy Memory at each step.

DIAGRAM

Evaluation and STEP-MFT Training Pipeline

This diagram shows how AdaMEM collects decision tuples with ADAMEM-HIGH, filters them with STEP-MFT, and evaluates on ALFWorld and WebShop.

PROCESS

How AdaMEM Handles a Long-Horizon Episode

  1. 01

    Long-Term Trajectory Memory Construction

    AdaMEM first builds Long-Term Trajectory Memory M offline from successful trajectories, storing state embeddings and future action sequences for dense retrieval.

  2. 02

    Short-Term Strategy Memory Synthesis

    At test time, AdaMEM retrieves experiences E_ret and generates Short-Term Strategy Memory z_t conditioned on the current state to guide immediate decisions.

  3. 03

    ADAMEM-HIGH and ADAMEM-LOW Inference

    Using ADAMEM-HIGH or ADAMEM-LOW, AdaMEM decides when to refresh strategies, trading off token cost against adaptability during the episode.

  4. 04

    STEP-MFT Strategy Fine-Tuning

    With STEP-MFT, AdaMEM filters successful, action-changing strategies and performs supervised fine-tuning so future strategies more reliably alter actions toward success.

KEY CONTRIBUTIONS

Key Contributions

  • 01

    Adaptive Memory Agent (ADAMEM)

    AdaMEM introduces a hybrid memory framework combining Long-Term Trajectory Memory and Short-Term Strategy Memory to enable continuous test-time adaptation without parameter updates, yielding up to 13% relative gains on ALFWorld.

  • 02

    STEP-MFT for Strategy Learning

    AdaMEM proposes STEP-MFT, a step-wise Memory Fine-Tuning technique that filters strategies by outcome success and action change to train high-utility strategy generation.

  • 03

    Scaling Dimension for Agentic Memory

    AdaMEM demonstrates a new scaling dimension where increasing retrieval budget k and adaptation effort improves performance, achieving up to 17% relative gains on ALFWorld and 13% on WebShop over static memory baselines.

RESULTS

By the Numbers

ALFWorld Seen Success Rate (%)

54.0%

+1.9 over Synapse

ALFWorld Unseen Success Rate (%)

58.2%

+6.0 over Synapse

WebShop Task Score

74.2

+2.8 over No Memory

HotpotQA Success Rate (%)

41.1%

+0.7 over ReasoningBank

On ALFWorld and WebShop, which test embodied navigation and web shopping, AdaMEM’s dynamic memory raises unseen ALFWorld success to 58.2% and WebShop Task Score to 74.2, surpassing static memories like Synapse and ReasoningBank. On HotpotQA cross-episode search, AdaMEM reaches 41.1% Success Rate, slightly ahead of both static memory baselines.

BENCHMARK

By the Numbers

On ALFWorld and WebShop, which test embodied navigation and web shopping, AdaMEM’s dynamic memory raises unseen ALFWorld success to 58.2% and WebShop Task Score to 74.2, surpassing static memories like Synapse and ReasoningBank. On HotpotQA cross-episode search, AdaMEM reaches 41.1% Success Rate, slightly ahead of both static memory baselines.

BENCHMARK

Training-free Memory Mechanisms on ALFWorld Unseen Split

Success Rate (%) on ALFWorld unseen for different memory mechanisms with Qwen3-4B-Instruct.

KEY INSIGHT

The Counterintuitive Finding

On WebShop, static memories hurt performance: Synapse drops Task Score from 71.4 with No Memory down to 65.4, a 6.0 point decrease.

This is surprising because more experience usually helps, but retrieving full trajectories at episode start from an uninformative homepage injects noisy priors that mislead the agent.

WHY IT MATTERS

What this unlocks for the field

AdaMEM unlocks agents that can continuously adapt strategies at test time using external experience, without any online parameter updates or extra critics.

Builders can now scale memory banks and test-time compute to trade tokens for robustness, enabling self-evolving agents in navigation, web interaction, and multi-hop search settings.

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