MemoryRewardBench: Benchmarking Reward Models for Long-Term Memory Management in Large Language Models

AuthorsZecheng Tang, Baibei Ji, Ruoxi Sun et al.

2026

TL;DR

MemoryRewardBench uses long-context reasoning, multi-turn dialogue, and long-form generation settings to reveal that GLM4.5-106A12B reaches 68.21 average accuracy and narrows the gap with proprietary reward models.

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THE PROBLEM

Reward models cannot reliably judge intermediate memory in long contexts

Existing memory benchmarks evaluate LLMs directly, while MemoryRewardBench highlights that automated RM-based memory assessment remains largely unexplored and unreliable.

When reward models misjudge intermediate memories in long-context reasoning or multi-turn dialogue, downstream supervision fails, degrading long-term consistency, temporal reasoning, and constraint-following.

HOW IT WORKS

MemoryRewardBench — Reward models for long-term memory management

MemoryRewardBench builds on Sequential Pattern, Parallelism Pattern, Mixed Pattern, Long-context Reasoning, Multi-turn Dialogue Understanding, and Long-form Generation to generate paired memory trajectories.

Think of MemoryRewardBench as a stress-test lab where different memory pipelines are like distinct circuits, and reward models act as judges scoring how cleanly information flows.

This design lets MemoryRewardBench probe process-based memory quality, not just final answers, revealing where plain long context windows fail to capture nuanced memory management.

DIAGRAM

MemoryRewardBench task flow across reasoning, dialogue, and generation

This diagram shows how MemoryRewardBench instantiates long-context reasoning, multi-turn dialogue understanding, and long-form generation tasks with specific memory patterns.

DIAGRAM

Evaluation pipeline for reward models on MemoryRewardBench

This diagram shows how MemoryRewardBench feeds paired trajectories to reward models and computes judgment accuracy across 10 settings and 2,400 examples.

PROCESS

How MemoryRewardBench Handles a Memory Management Evaluation Session

  1. 01

    Memory Management Pattern

    MemoryRewardBench first selects Sequential Pattern, Parallelism Pattern, or Mixed Pattern to define how intermediate memories evolve over chunks.

  2. 02

    Task Overview

    MemoryRewardBench instantiates Long-context Reasoning, Multi-turn Dialogue Understanding, or Long-form Generation with context lengths from 8K to 128K tokens.

  3. 03

    Benchmark Construction

    MemoryRewardBench builds chosen and rejected trajectories using NOISE, DROP, Mem0, AMem, and constraint perturbations while keeping outcomes or processes controlled.

  4. 04

    RM Evaluation Criteria

    MemoryRewardBench applies outcome-based and process-based criteria, asking reward models to pick the better trajectory and justify their choice.

KEY CONTRIBUTIONS

Key Contributions

  • 01

    Introduce MemoryRewardBench

    MemoryRewardBench is the first benchmark targeting reward models, with 10 settings and 2,400 examples spanning 8K to 128K-token contexts for memory management evaluation.

  • 02

    Define memory management patterns

    MemoryRewardBench formalizes Sequential Pattern, Parallelism Pattern, and Mixed Pattern, showing how intermediate memories M evolve and fuse to produce outcomes.

  • 03

    Cross-task RM analysis

    MemoryRewardBench compares 13 reward models on long-context reasoning, multi-turn dialogue, and long-form generation, revealing GLM4.5-106A12B at 68.21 vs Claude-Opus-4.5 at 74.75 average accuracy.

RESULTS

By the Numbers

Avg.

74.75

+6.54 over GLM4.5-106A12B

Long-context Reasoning Avg.

68.88

Claude-Opus-4.5 vs 69.13 for GLM4.5-106A12B

Multi-turn Dialogue Avg.

64.07

Claude-Opus-4.5 vs 56.75 for GLM4.5-106A12B

Long-form Generation Avg.

74.75

Claude-Opus-4.5 vs 68.21 for GLM4.5-106A12B

MemoryRewardBench evaluates reward models on 10 settings built from LongBench, RULER, LoCoMo, LongEval, LongGenBench, and LongProc. The 74.75 average accuracy for Claude-Opus-4.5 shows that current best reward models still make roughly one in four incorrect memory management judgments.

BENCHMARK

By the Numbers

MemoryRewardBench evaluates reward models on 10 settings built from LongBench, RULER, LoCoMo, LongEval, LongGenBench, and LongProc. The 74.75 average accuracy for Claude-Opus-4.5 shows that current best reward models still make roughly one in four incorrect memory management judgments.

BENCHMARK

Results on MemoryRewardBench across proprietary and open-source reward models

Average accuracy on MemoryRewardBench over all task settings.

KEY INSIGHT

The Counterintuitive Finding

MemoryRewardBench shows Qwen3-4B at 52.42 average accuracy, surpassing the larger Qwen2.5-7B which only reaches 38.17.

This breaks the common assumption that more parameters always help reward modeling, highlighting a strong generational advantage over raw model size.

WHY IT MATTERS

What this unlocks for the field

MemoryRewardBench gives practitioners a concrete way to benchmark reward models on long-term memory management rather than only final-answer quality.

Builders can now choose and train reward models that explicitly favor clean, coherent memory trajectories, enabling more reliable supervision of memory-centric LLM systems.

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