docs: Round 6b results — Kotlin capture fix + minimal coarsening

experiments/EXPERIMENT_LOG.md

@@ -152,6 +152,37 @@ depends on how rich the highlights.scm is.
 
 ---
 
+## Round 6b: Kotlin Capture Fix + Minimal Coarsening
+
+**Hypothesis:** Kotlin's highlights.scm uses bare captures (`conditional`,
+`exception`, `repeat`) while `BEHAVIORAL_PREFIXES` expected dotted forms
+(`keyword.conditional`, etc.). All Kotlin structural context was being dropped.
+
+**Method:** Added bare captures to BEHAVIORAL_PREFIXES. Dropped ATTR, TYPE,
+VAR from coarsening (too noisy). Only coarsen RETURN, IF, EXCEPTION, LOOP.
+
+**Result:**
+
+| Codebase | Raw coverage | Coarsened coverage | Cross-pkg contexts |
+|----------|-------------|-------------------|-------------------|
+| RAGSAK k=3 | 18.5% | 6.0% | 87 (was 69) |
+| Flask k=2 | 4.5% | 15.8% | 35 (was 54) |
+| Flask k=3 | 17.1% | 17.3% | 28 (was 40) |
+
+Key cross-package patterns (coarsened):
+- `('IF', 'isEmpty', 'isEmpty')` — 8 RAGSAK packages (null-check convention)
+- `('IF', 'isNullOrBlank', 'isNullOrBlank')` — 6 RAGSAK packages
+- `('RETURN', 'render_template', 'render_template')` — 5 Flask packages
+- `('IF', 'RETURN')` — 8 RAGSAK packages (guard clause pattern)
+
+**Verdict:** The 4 high-signal categories (RETURN, IF, EXCEPTION, LOOP) DO
+reveal cross-package conventions. Coarsening trades per-package coverage for
+cross-package reach. Whether this is useful depends on the use case:
+- For code completion: raw is better (specific method names)
+- For documentation: coarsened is better (structural conventions)
+
+---
+
 ## What We Learned (Summary)
 
 1. **Per-package grouping is too sparse.** 1-3 sequences per package isn't