# Plan C Implementation: Better Intervention Sampling

## Goal
Improve intervention quality for more informative counterfactuals.

## Changes to Generation

### 1. Near-Miss Focus (50% of interventions)
- Small perturbations around expert action
- Gaussian noise: σ = 0.1 for position, σ = 0.05 for rotation
- Test both directions (±δ)

### 2. Decision Boundary Exploration (30%)
- Actions at success/failure boundary
- Perturb only critical dimensions
- Keep gripper state same as expert

### 3. Systematic Coverage (20%)
- Grid around expert action
- Cover action space uniformly
- Ensure diverse failure modes

### Old Distribution (K=16)
- Expert: 1
- Random: ~8-10
- Near-miss: ~3-5
- Structured: ~2-3

### New Distribution (K=16)
- Expert: 1
- Near-miss (small δ): 8 (50%)
- Decision boundary: 5 (30%)
- Systematic grid: 2 (20%)

## Expected Impact
- More informative comparisons
- Better gradient signal for ranking
- Clearer success/failure patterns
- **+2-3% performance gain**

## Implementation
File: `scripts/generate_maniskill_lattice.py`
Function: `sample_candidate_actions()`

Add `--candidate-mode enhanced` flag.