The earlier synthetic bend (IP3 at (6, 2)) put IP4 ahead of IP3 on the turned line, so the axis folded back on itself. buildPier now refuses a kink behind IP1 along IP1→IP2 or an IP3 behind the kink along the turned direction. Tests use IP3 (9, −3.464), a valid 60° right turn with kink (7, 0). Co-Authored-By: Claude Haiku 5.5 <noreply@anthropic.com>