MemGround: Long-Term Memory Evaluation Kit for Large Language Models in Gamified Scenarios

AuthorsYihang Ding, Wanke Xia, Yiting Zhao et al.

2026

TL;DR

MemGround uses a three-tier game-based memory framework plus multi-dimensional metrics to show GPT-5.2 falls to 23.61% QA Overall in Reasoning-Based Memory.

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THE PROBLEM

Static long-term memory tests miss dynamic tracking and reasoning

MemGround argues that current long-term memory evaluations are "fundamentally static", fixating on simple retrieval and short-context inference while ignoring dynamic state tracking.

This failure mode appears in interactive assistants and investigative agents, where missing dynamic, hierarchical, and associative memory leads to broken timelines and incoherent multi-step reasoning.

HOW IT WORKS

MemGround — three-tier hierarchical memory in gamified scenarios

MemGround’s core mechanism is a three-tier hierarchical memory evaluation framework plus a human-grounded data construction pipeline and unified interactive evaluation framework over TRPG, No Case Should Remain Unsolved, and Type Help.

You can think of MemGround like a layered memory lab: TRPG tests RAM-like Surface State Memory, No Case Should Remain Unsolved probes timeline stitching, and Type Help stresses disk-like Reasoning-Based Memory over a clue graph.

This design lets MemGround expose failures in dynamic tracking, temporal association, and DAG-style reasoning that a plain context window benchmark cannot reveal.

DIAGRAM

MemGround interaction loop in gamified environments

This diagram shows how MemGround runs an agent-environment loop to test long-term memory across TRPG, No Case Should Remain Unsolved, and Type Help.

DIAGRAM

MemGround data and evaluation pipeline

This diagram shows how MemGround constructs human-grounded JSON cases and then evaluates LLMs with multi-dimensional metrics.

PROCESS

How MemGround Handles an Interactive Evaluation Session

  1. 01

    Environment Initialization

    MemGround uses Environment Initialization to load a specific TRPG, No Case Should Remain Unsolved, or Type Help JSON scenario and build prompts for the agent.

  2. 02

    Agent Interaction Loop

    In the Agent Interaction Loop, MemGround repeatedly feeds observations, lets the agent choose retrieval or actions, and updates game states to simulate long-term interaction.

  3. 03

    Memory Management

    During Memory Management, MemGround applies StoreMemory, CompressMemory, RetrieveMemory, and IndexMemory to track fragments under realistic context window constraints.

  4. 04

    End Evaluation

    At End Evaluation, MemGround computes QA Overall, MFU, MFCO, and ETD to summarize the agent’s dynamic tracking, temporal ordering, and reasoning-based memory.

KEY CONTRIBUTIONS

Key Contributions

  • 01

    Three-tier hierarchical memory evaluation framework

    MemGround introduces Surface State Memory, Temporal Associative Memory, and Reasoning-Based Memory, each grounded in a distinct game scenario and evaluated with QA Overall.

  • 02

    Multi-dimensional metric suite for memory

    MemGround defines QA Overall, Memory Fragments Unlocked (MFU), Memory Fragments with Correct Order (MFCO), and Exploration Trajectory Diagrams (ETD) to capture both outcomes and trajectories.

  • 03

    Game Ground with human-grounded pipeline

    MemGround builds Game Ground via human annotation, calibration, and structured JSON, then evaluates closed-source and open-source models plus Mem0 and A-MEM memory agents.

RESULTS

By the Numbers

QA Overall TRPG

51.51%

+25.73 over Qwen3-VL-32B-Instruct In-context

QA Overall No Case

47.76%

vs Gemini-3-Pro-Preview 41.61% in Surface and Temporal tasks

MFCO No Case

45.46%

temporal ordering accuracy for Gemini-3-Pro-Preview in No Case Should Remain Unsolved

MFU Type Help

50.91%

file discovery rate for Gemini-3-Pro-Preview in Reasoning-Based Memory scenario

MemGround’s main table reports QA Overall, MFU, and MFCO across TRPG, No Case Should Remain Unsolved, and Type Help. These results show that even GPT-5.2 and Gemini-3-Pro-Preview struggle with Reasoning-Based Memory despite stronger Surface State Memory performance.

BENCHMARK

By the Numbers

MemGround’s main table reports QA Overall, MFU, and MFCO across TRPG, No Case Should Remain Unsolved, and Type Help. These results show that even GPT-5.2 and Gemini-3-Pro-Preview struggle with Reasoning-Based Memory despite stronger Surface State Memory performance.

BENCHMARK

MemGround main results across TRPG, No Case Should Remain Unsolved, and Type Help

QA Overall (%) for GPT-5.2 configurations on MemGround’s three game scenarios.

KEY INSIGHT

The Counterintuitive Finding

MemGround shows GPT-5.2 drops from 51.51% QA Overall in TRPG to just 23.61% QA Overall in Type Help, despite being a frontier model.

This is counterintuitive because GPT-5.2 is strong at long-context reasoning, yet MemGround reveals that dynamic reasoning-based memory over fragmented clues remains severely limited.

WHY IT MATTERS

What this unlocks for the field

MemGround unlocks a way to stress-test hierarchical memory in realistic interactive games, exposing failures in state tracking, temporal association, and DAG-style reasoning.

With MemGround, builders can design and debug memory agents like Mem0 and A-MEM against rich trajectories, rather than relying on static QA benchmarks that hide long-term reasoning breakdowns.

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