{
  "experiment": "Gemma 4 V4 input-variation SAE (bnb 4-bit)",
  "caveat_quantization": "4-bit quantized inference; results characterize quantized checkpoint.",
  "prompt_equivalence": "DIAGNOSTIC ONLY: inputs DIFFER across neutral / V0 / V3 templates. This SAE is an input-classifier baseline, NOT a behavior detector. Cohen's d here captures input-template separability, not generation-process separability.",
  "model": {
    "key": "gemma4_e2b",
    "hf_name": "google/gemma-4-E2B",
    "d_in": 1536,
    "layer": 17,
    "quantization": "bnb 4-bit nf4 double_quant fp16_compute"
  },
  "sae": {
    "architecture": "topk",
    "k": 32,
    "d_sae": 6144,
    "metrics": {
      "mse_loss": 0.02122976817190647,
      "explained_variance": 0.9926107570635635,
      "l0": 32.0,
      "alive_features": 241,
      "train_time_s": 110.0,
      "num_activations": 3619,
      "final_epoch_loss": 0.021807
    },
    "checkpoint": "gemma4_e2b_v4input_topk_k32_L17_bnb4bit.pt"
  },
  "input_split": {
    "n_neutral": 50,
    "n_v0": 50,
    "n_v3": 50,
    "neutral_vs_v0_block": {
      "label": "input_neutral_vs_v0",
      "d_max": 7.808701515197754,
      "d_mean": 0.0064131771214306355,
      "d_above_1": 11,
      "d_above_2": 1,
      "top10_ids": [
        2196,
        477,
        2905,
        4422,
        414,
        1729,
        2933,
        2682,
        4232,
        1926
      ],
      "top10_d": [
        7.808701515197754,
        1.8714970350265503,
        1.7008979320526123,
        1.686379313468933,
        1.5654693841934204,
        1.2770538330078125,
        1.2198415994644165,
        1.1726460456848145,
        1.1275814771652222,
        1.085732102394104
      ]
    },
    "neutral_vs_v3_block": {
      "label": "input_neutral_vs_v3",
      "d_max": 9.32315731048584,
      "d_mean": 0.010321254841983318,
      "d_above_1": 14,
      "d_above_2": 6,
      "top10_ids": [
        2196,
        3340,
        4259,
        519,
        4232,
        477,
        3928,
        1926,
        561,
        2905
      ],
      "top10_d": [
        9.32315731048584,
        4.7347235679626465,
        2.557842254638672,
        2.2542951107025146,
        2.1295456886291504,
        2.0010032653808594,
        1.7745753526687622,
        1.6784650087356567,
        1.6581165790557861,
        1.6453344821929932
      ]
    }
  },
  "timestamp": "2026-04-20T08:26:20.056190+00:00"
}