{
  "paper": {
    "arxiv_id": "2607.24015",
    "title": "Mosaic: A Fleet of User Embedding Specialists for Recommendation at Meta",
    "url": "https://arxiv.org/abs/2607.24015",
    "organization": "Meta"
  },
  "dataset": {
    "name": "MovieLens-1M",
    "users": 320,
    "items": 480
  },
  "setup": {
    "seed": 42,
    "steps_per_model": 120,
    "specialists": [
      "memorization",
      "dense-heavy",
      "sequential",
      "CoTrain-MoE"
    ],
    "same_split_and_full_catalog": true
  },
  "baseline": {
    "name": "single sequential user embedding",
    "hit_at_10": 0.040625,
    "ndcg_at_10": 0.016438474697594883,
    "head_share_at_10": 0.1346875
  },
  "method": {
    "name": "Mosaic fleet + MRM + CRL",
    "hit_at_10": 0.0375,
    "ndcg_at_10": 0.017012855123840185,
    "head_share_at_10": 0.1553125
  },
  "relative": {
    "hit_at_10_percent": -7.692307692307699,
    "ndcg_at_10_percent": 3.494122397678052,
    "head_share_at_10_percent": 15.313225058004646
  },
  "training": {
    "baseline": {
      "initial_loss": 6.909626388549805,
      "final_loss": 6.273937082290649,
      "final_cosine_redundancy": null,
      "final_mrm_loss": null,
      "parameters": 45800,
      "device": "mps"
    },
    "mosaic": {
      "initial_loss": 6.958033609390259,
      "final_loss": 6.358517169952393,
      "final_cosine_redundancy": -0.1508315160870552,
      "final_mrm_loss": 1.2512000918388366,
      "parameters": 49256,
      "device": "mps"
    }
  },
  "paper_results": {
    "surface_1_percent": 0.1,
    "surface_2_percent": 0.15,
    "surface_3_percent": 0.28,
    "gpu_serving_reduction_percent": 79,
    "coevaluation_speedup": "3-5x"
  },
  "scope": "实际训练 memorization、dense-heavy、GRU sequential 与 routed CoTrain-MoE 四种 specialist，执行二任务笛卡尔积 MRM 辅助分类、warm-up cosine redundancy loss 和下游全目录排序。MovieLens genre/popularity 代理 Meta 私有多表面行为标签；未复刻 HSTU 2048、跨产品特征、CoEval 与线上混合 serving。",
  "runtime": {
    "requested_device": "mps",
    "cpu_threads": null,
    "platform": "macOS arm64",
    "resolved_device": "mps",
    "torch_version": "2.13.0",
    "accelerator": "Apple Metal Performance Shaders"
  },
  "reproduction_fidelity": {
    "level": "core_mechanism",
    "label": "核心机制复现",
    "description": "论文中心算法被实际执行，但生产模型、私有特征或基础设施未复刻。",
    "omitted_core_components": [
      "Meta private multi-surface features and labels",
      "HSTU-2048 specialists and production-scale CoTrain",
      "CoEval, zero-out evaluation, AOTI and hybrid serving"
    ]
  },
  "schema_version": 2,
  "manifest_ref": "reproduction:mosaic",
  "evaluation_protocol": {
    "tier": "l2_public_dataset",
    "seeds": [
      42
    ],
    "formal_comparison": false,
    "claim_policy": "single/few-seed smoke result; do not claim a stable improvement"
  },
  "provenance": {
    "artifact_path": "docs/reproductions/2607.24015-mosaic/metrics/movielens-1m-seed42.json",
    "historical_migration": "historical-metrics-v2-2026-08-09",
    "original_code_commit": "not recorded",
    "dataset_fingerprint": "not recorded in historical artifact"
  }
}