At equal compute (250 updates either way, 5.8x the samples) the new loop beats
the baseline against heuristic_expert: 0.4525 -> 0.5071 win rate, -4.28 ->
-0.56 mean score diff. Expert ends rounds at their natural length, so that is
a clean read on card play.
It appears to *lose* ground against heuristic_balanced (0.9866 -> 0.9292), but
that is entirely the MAX_STEPS=400 cap. Drawing from a discard pile does not
deplete the deck, so a round can be stalled indefinitely; against a weak
opponent the extra turns are worth points, and with 5.8x the samples the agent
learns the exploit harder (greedy rounds run 225 plies). Splitting 2048 games:
naturally-ended games lose 0.08%, cap-hit games lose 20.62%, and 99.4% of all
losses land in cap-hit games. The board freezes mid-expedition and the -20s
stand.
Self-play does not have this failure mode -- league runs converge to 53.6-ply
rounds and never hit the cap -- which is the regime the 3-round work targets.
Noted in the plan: static heuristic anchors are unusable as gates, and the
per-round cap needs care in Phase 1.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XBQKgvBbxbheiTF1AVy1Sh
coolguyandClaude Opus 4.8
47d0e803f5