Memory Evaluation - Mem0

Why Memory Evaluation Matters

Most AI agent memory systems retrieve information by maximizing context window size. That works on benchmarks but not in production, where every token adds cost. Token efficiency means achieving high accuracy with less context per query. It is what separates benchmark performance from production viability. Mem0’s algorithm achieves competitive accuracy on LoCoMo, LongMemEval, and BEAM while averaging under 7,000 tokens per retrieval call. Full-context approaches on the same benchmarks routinely consume 25,000+ tokens per query. Unless noted otherwise, scores are reported at a top_200 retrieval budget (the 200 highest-ranked memories per query). Evaluating a memory system at scale comes down to three parameters: accuracy (what the benchmarks measure), cost (context tokens per query), and performance (latency). Optimizing one is easy. Balancing all three at scale is the actual problem.

Some benchmarks today, particularly smaller ones like LoCoMo and LongMemEval, can be materially improved by aggressive retrieval strategies, larger context windows, or frontier models. That does not necessarily mean the underlying memory system has gotten better. We evaluate under constraints that reflect how memory systems actually run in production: limited context windows and practical token budgets.

Architecture Overview

Mem0’s memory system operates across two phases, extraction (writing) and retrieval (reading), connected by a graph memory layer (entity linking) and a temporal reasoning layer (time metadata written during extraction and scored during retrieval).

Memory Extraction (Distillation)

When new conversations arrive, the extraction pipeline processes them through six stages:

1. Store New Memories: Conversation enters the pipeline asynchronously (after the agent responds)
2. Context Lookup: Find related existing memories to avoid duplicates
3. Distill Memories: Single-pass LLM extraction produces ADD-only facts from input + context
4. Deduplicate + Embed: Hash-based deduplication, then vectorize new memories
5. Graph Memory (Entity Linking): Identify entities (proper nouns, quoted text, compound noun phrases) and link them across memories into a graph
6. Temporal Reasoning: A separate temporal reasoning pass reads each new memory alongside the source conversation and its date, extracting temporal metadata: when the event occurred, whether it is ongoing or completed, how precise the timing is, and the memory type (event, state, plan, preference, relationship, absence). It is independent of extraction and can run asynchronously so writes stay fast; this metadata is stored with the memory and used later at retrieval.

Memories are distributed across three storage layers, each tuned for a specific retrieval pattern:

The key architectural decision is ADD-only extraction. New facts are stored alongside old ones. Nothing is overwritten or deleted. When information changes, both the old and new facts survive. This preserves temporal context and eliminates information loss from premature consolidation.

Multi-Signal Retrieval

When a query arrives, the retrieval pipeline scores candidates across multiple signals in parallel:

1. Semantic Search: Vector similarity scoring against memory embeddings
2. Keyword Search: Normalized term matching via BM25 with verb-form lemmatization
3. Entity Search: Entity matching boosts memories linked to query entities
4. Temporal Reasoning: The query’s temporal intent is classified (with no extra LLM call), then each candidate is scored by how well the temporal metadata extracted at write time matches that intent.

These signals are fused via rank scoring into the final top-K set. The temporal score is additive and semantic relevance always dominates; it nudges ranking toward the correct dated instance without filtering candidates out or overriding a strong semantic match, so relevant memories are never dropped. Different query types lean on different signals:

The combined score outperformed every individual signal across every category tested.

Benchmarks

LoCoMo

LoCoMo tests single-hop, multi-hop, open-domain, and temporal memory recall across conversational sessions.

Mean tokens: 6,956. Temporal reasoning is on by default and helps most on temporal (92.0) and multi-hop (91.3) questions, where the system has to identify which dated instance applies, while open-domain (72.7) does not benefit and is actively being tuned.

LongMemEval

LongMemEval evaluates memory across single-session and multi-session contexts, including knowledge updates and temporal reasoning.

Mean tokens: 6,787. Temporal reasoning is the standout at a top_200 budget, reaching 97.0 on the temporal-reasoning category, with single-session user and assistant both near-saturated (98.6 and 98.2). Knowledge update (93.6) remains the hardest category for an additive, ADD-only architecture: older facts are preserved rather than overwritten, so semantically similar prior facts can still surface alongside newer ones.

BEAM

BEAM evaluates memory systems at 1M and 10M token scales across ten task categories. It is the only public benchmark that operates at context volumes production AI agents actually encounter.

Mean tokens (1M): 6,719. Mean tokens (10M): 6,914. BEAM is the most relevant benchmark here. It operates at 1M and 10M token scales and cannot be solved by simply expanding the context window. The results at 10M reflect where memory systems actually stand at production context volumes. The system holds up well on preference following, instruction following, and knowledge updates at both scales. Weaker categories at 10M (temporal reasoning, event ordering, multi-session reasoning) are open problems across the field. They require higher-order representations of how events relate to each other across time, which is a primary focus of our ongoing research.

Performance Summary

All results use a single-pass retrieval setup (one retrieval call, one answer, no agentic loops) at a top_200 retrieval budget.

Scores reflect Mem0’s managed platform, which includes proprietary optimizations not available in the open-source SDK. Open-source users should expect directionally similar gains but not identical numbers. All benchmarks run on the same production-representative model stack. Scores carry a ±1 point confidence interval due to judge inconsistency.

Running Evaluations

The full evaluation framework is open-sourced so anyone can reproduce the numbers independently. It supports both Mem0 Cloud and self-hosted OSS backends.

Setup

• Mem0 Cloud
• Mem0 OSS (Docker)

git clone https://github.com/mem0ai/memory-benchmarks.git
cd memory-benchmarks
pip install -r requirements.txt

# Set your API keys
export MEM0_API_KEY=m0-your-key
export OPENAI_API_KEY=sk-your-key

git clone https://github.com/mem0ai/memory-benchmarks.git
cd memory-benchmarks
pip install -r requirements.txt

# Copy and configure environment
cp .env.example .env
# Edit .env to add OPENAI_API_KEY

# Start local Mem0 server + Qdrant
docker compose up -d
# Mem0 server: http://localhost:8888
# Qdrant:      http://localhost:6333

Running a Benchmark

Each benchmark is a Python module with its own runner ( source code). All share common CLI options:

# ~300 questions across 10 conversations (fastest benchmark)
python -m benchmarks.locomo.run \
  --project-name my-eval \
  --backend cloud \
  --mem0-api-key $MEM0_API_KEY \
  --top-k 200

# Self-hosted
python -m benchmarks.locomo.run \
  --project-name my-eval \
  --top-k 200

# 500 questions across 6 categories
python -m benchmarks.longmemeval.run \
  --project-name my-eval \
  --backend cloud \
  --mem0-api-key $MEM0_API_KEY \
  --all-questions \
  --top-k 200

# Self-hosted
python -m benchmarks.longmemeval.run \
  --project-name my-eval \
  --all-questions \
  --top-k 200

# 1M token scale (100 conversations)
python -m benchmarks.beam.run \
  --project-name my-eval \
  --backend cloud \
  --mem0-api-key $MEM0_API_KEY \
  --chat-sizes 1M \
  --conversations 0-99 \
  --top-k 200

# 10M token scale
python -m benchmarks.beam.run \
  --project-name my-eval \
  --backend cloud \
  --mem0-api-key $MEM0_API_KEY \
  --chat-sizes 10M \
  --conversations 0-99 \
  --top-k 200

Custom Model Configuration

To run evaluations with custom models (Azure OpenAI, Ollama, etc.), copy one of the provided configs:

# Available configs: openai.yaml, azure-openai.yaml, ollama.yaml
cp configs/azure-openai.yaml mem0-config.yaml
# Edit mem0-config.yaml with your model details

# Uncomment the volume mount in docker-compose.yml, then restart:
docker compose down && docker compose up -d

Viewing Results

Results are saved to results/[benchmark]/ and can be explored through the built-in web UI:

npm install
npm run dev -- -p 3001
# Open http://localhost:3001

The UI lets you browse per-question results, inspect retrieval details, and compare multiple runs.

Result Format

Each evaluated question produces a structured result:

{
  "id": "locomo_q_001",
  "group": "temporal",
  "question": "When did the user first mention moving?",
  "ground_truth": "During the March 3rd conversation",
  "retrieval": {
    "search_query": "when did user mention moving",
    "search_results": ["..."],
    "search_latency_ms": 123.4,
    "total_results": 42
  },
  "generation": {
    "generated_answer": "The user first mentioned moving on March 3rd",
    "model": "<answerer-model>",
    "prompt_tokens": 500,
    "completion_tokens": 100
  },
  "judgment": {
    "judgment": "CORRECT",
    "score": 0.85,
    "reason": "Answer correctly identifies the date",
    "model": "<judge-model>"
  },
  "cutoff_results": {
    "top_10": { "score": 0.75, "judgment": "CORRECT" },
    "top_50": { "score": 0.85, "judgment": "CORRECT" },
    "top_200": { "score": 0.90, "judgment": "CORRECT" }
  }
}

Interpreting Results

When evaluating memory systems, keep these considerations in mind:

• Saturating a small benchmark is not the same as building a memory system that works at scale. Small benchmarks can be brute-forced with aggressive retrieval and frontier models.
• Token efficiency matters as much as accuracy. A system that scores 95% using 25K tokens per query isn’t comparable to one scoring 90% using 7K tokens. Report mean tokens per query alongside scores.
• Compare at equal constraints. Always compare systems using the same retrieval budget, the same model, and the same latency budget. A frontier model at maximum recall is not comparable to a smaller production-grade model at production-realistic retrieval depth.
• Watch for score ceiling effects. Categories like “single-session user” are already near-saturated (97%+). Improvements in these categories are less meaningful than gains in harder categories like temporal reasoning or multi-session.
• BEAM at 10M is the real test. Any system can look good at small scale. The 10M-token BEAM benchmark reveals whether the retrieval system actually scales.

FAQ

What judge model is used for evaluation?

The judge model is configurable via --judge-model and --judge-provider flags. See the evaluation repository for the current defaults. Scores carry a ±1 point confidence interval due to judge inconsistency.

Can I evaluate with a different extraction model?

Yes. For self-hosted, configure the extraction model in your mem0-config.yaml (see the configs/ directory of the evaluation repo for provider-specific examples). For Mem0 Cloud, extraction uses the platform’s default. Using a frontier model will likely produce higher scores but at higher cost and latency.

Why are BEAM scores lower than LoCoMo/LongMemEval?

BEAM operates at 1M and 10M token scales, orders of magnitude larger than LoCoMo or LongMemEval. At these scales, similar content appears multiple times across the window, and the memory system must surface the exact correct memory over many close matches. The scores reflect the genuine difficulty of the task, not a regression in the algorithm.

How do I contribute a new benchmark?

Open a pull request to the memory-benchmarks repository with your benchmark implementation. See the repository README for the expected interface and format.

Resources

[**Evaluation Repository**

Open-source evaluation framework for reproducing all benchmark results](https://github.com/mem0ai/memory-benchmarks)

[**Research**

Published research papers and technical reports](/content/research/index.html)

[**Blog Post**

Detailed writeup of the new algorithm design and results](/content/blog/the-token-efficient-memory-algorithm-now-has-temporal-reasoning/index.html)

[**Platform Migration**

Guide for migrating your Platform integration](https://docs.mem0.ai/migration/platform-v2-to-v3)