{
  "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": 10,
    "quantization": "bnb 4-bit nf4 double_quant fp16_compute"
  },
  "sae": {
    "architecture": "topk",
    "k": 32,
    "d_sae": 6144,
    "metrics": {
      "mse_loss": 0.007008623331785202,
      "explained_variance": 0.9957067616251516,
      "l0": 32.0,
      "alive_features": 559,
      "train_time_s": 108.4,
      "num_activations": 3619,
      "final_epoch_loss": 0.00756
    },
    "checkpoint": "gemma4_e2b_v4input_topk_k32_L10_bnb4bit.pt"
  },
  "input_split": {
    "n_neutral": 50,
    "n_v0": 50,
    "n_v3": 50,
    "neutral_vs_v0_block": {
      "label": "input_neutral_vs_v0",
      "d_max": 16.963083267211914,
      "d_mean": 0.011611283756792545,
      "d_above_1": 18,
      "d_above_2": 8,
      "top10_ids": [
        4775,
        1592,
        1349,
        4973,
        2951,
        849,
        5594,
        5259,
        4368,
        5822
      ],
      "top10_d": [
        16.963083267211914,
        8.70340633392334,
        3.4786453247070312,
        3.3507778644561768,
        3.049485206604004,
        2.4634058475494385,
        2.374709367752075,
        2.126396656036377,
        1.9656071662902832,
        1.7550815343856812
      ]
    },
    "neutral_vs_v3_block": {
      "label": "input_neutral_vs_v3",
      "d_max": 8.594282150268555,
      "d_mean": 0.010855759494006634,
      "d_above_1": 20,
      "d_above_2": 10,
      "top10_ids": [
        1592,
        5594,
        3907,
        5560,
        4020,
        4912,
        849,
        995,
        1349,
        3968
      ],
      "top10_d": [
        8.594282150268555,
        7.050577163696289,
        5.138309478759766,
        3.4406070709228516,
        3.346367835998535,
        2.9664735794067383,
        2.887408494949341,
        2.620266914367676,
        2.325357675552368,
        2.1497621536254883
      ]
    }
  },
  "timestamp": "2026-04-21T06:46:21.923664+00:00"
}