{
  "experiment": "Three-way ablation: does the coverage FLOOR add value over subspace-only pruning?",
  "modality": "LIDC-IDRI", "layer": 3, "lesion_size": "small (1-3 patches)", "n_slices": 400,
  "strategies": {
    "saliency": "top-k by final-block attention",
    "subspace_only": "top-k by block-3 density-A membership (NO floor)",
    "subspace_floor": "constrained pruner (Gumbel + dual mu + coding-rate coverage), epsilon calibrated so MEAN budget == k (adaptive per-image)"
  },
  "results": {
    "0.25": {"k": 49, "floor_mean_k": 48.9, "saliency_recall": 0.521, "subspace_only_recall": 0.817,
             "subspace_floor_recall": 0.219,
             "floor_minus_subspace": {"diff": -0.598, "ci95": [-0.646, -0.545], "excludes_0": true},
             "subspace_minus_saliency": {"diff": 0.296, "ci95": [0.245, 0.343], "excludes_0": true}},
    "0.5": {"k": 98, "floor_mean_k": 98.6, "saliency_recall": 0.827, "subspace_only_recall": 0.981,
            "subspace_floor_recall": 0.460,
            "floor_minus_subspace": {"diff": -0.521, "ci95": [-0.565, -0.475], "excludes_0": true},
            "subspace_minus_saliency": {"diff": 0.154, "ci95": [0.120, 0.190], "excludes_0": true}}
  },
  "floor_adds_value_over_subspace": false,
  "verdict": "NEGATIVE RESULT for the coverage floor. At matched budget the constrained coverage-floor pruner retains FAR FEWER small lesions than simple subspace-membership top-k (0.22 vs 0.82 @0.25; 0.46 vs 0.98 @0.5), CI excludes 0. The floor does not merely add little -- it HURTS.",
  "root_cause": "The coverage functional C(S;x) = effective-rank / coding-rate of the lesion-subspace projection rewards DIVERSE SPANNING of the subspace, not CONCENTRATION on the few high-membership lesion tokens. Constrained optimization to preserve coverage therefore retains a diverse spanning set and drops the actual (few, low-diversity) lesion tokens. Top-k by membership keeps lesion tokens directly. (An ENERGY coverage = sum ||P_L z||^2 would align with membership -- but then the 'floor' reduces to membership top-k and adds nothing.)",
  "reframing": "The contribution is the LABEL-FREE LESION SUBSPACE + membership pruning + per-image certificate, NOT the coverage-constrained optimization / interpretable dual. The subspace localizes lesions without labels across modalities (CT 0.87, US 0.73) and backbones (MedDINOv3, DINOv2), and subspace-membership pruning beats saliency pruning on small-lesion miss-rate (Gate 3). The constrained-optimization 'coverage floor' with a dual controller -- the formalization's centerpiece -- is an honest NEGATIVE: effective-rank coverage is misaligned with lesion-token retention.",
  "consistency": "Coheres with Gate 4 (money plot didn't emerge: aggregate coverage is insensitive to small lesions) and Gate 2 (coverage no more faithful than saliency). All three trace to one fact: effective-rank coverage is a poor instrument for SMALL lesions, which are few, high-membership, low-diversity tokens.",
  "artifact": "ablation_floor.json",
  "human_signoff": null
}