notes(bf-59h): document that work was already completed in commit d42d1a5

notes/bf-59h.md

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+# Bead bf-59h: Evolver fitness weight combat kill rate alongside win rate
+
+## Status: Already Completed
+
+This bead's work was already completed in commit `d42d1a533664bb4933845f2a45b032288aa08be8` on 2026-06-17.
+
+## What Was Done
+
+The commit already implements all requirements from the bead description:
+
+1. ✅ **Fitness Formula Updated** (`cmd/acb-evolver/run.go` lines 601-608)
+   - Changed from: `fitness = winRate` (win rate only)
+   - Changed to: `fitness = 0.7*winRate + 0.3*killRate`
+   - This weights combat aggression at 30% alongside 70% win rate
+
+2. ✅ **Kill Tracking Added** (`cmd/acb-evolver/internal/arena/arena.go`)
+   - `ArenaResult` now includes: `TotalKills`, `TotalMatches`, `KillRate`
+   - Kill rate is computed as: `TotalKills / TotalMatches` (excluding error matches)
+   - Combat deaths are tracked per match via `CombatDeaths []int` field
+
+3. ✅ **System Prompt Updated** (`cmd/acb-evolver/internal/prompt/builder.go` lines 154-159)
+   - Added explicit "Fitness Function" section explaining the 70/30 formula
+   - Includes language: "combat kills and eliminations are valuable, not just resource foraging"
+   - Emphasizes: "Aggressive combat strategies that secure kills while winning are strongly favored"
+
+4. ✅ **Enhanced Logging** (`cmd/acb-evolver/run.go` line 622-625)
+   - Arena logging now shows: `win_rate`, `kill_rate`, `total kills`, `total matches`, `fitness`
+
+## Verification
+
+The implementation correctly addresses the bead's requirements:
+- Fitness is now a weighted combination (70% win rate, 30% kill rate)
+- Kill data is available from match records (via `CombatDeaths` field in game engine results)
+- System prompt explicitly informs the LLM that kill score has value
+- The evolver will now select for combat aggression, not just win optimization
+
+## Dependencies Met
+
+The bead noted that it required `bf-z9m` (kill scoring) to be merged first. The current implementation shows that kill scoring data is already available in the match records, indicating that dependency has been met.