W12 L1 view: tile work 17.3 worker-s finishes 4 ms from ideal 12-way scaling; the remaining ~0.28 s is startup (shape compile 215 ms). Largest lever: LOD1 density-grid fill (3.35 worker-s; proof blocks are gated to steps 1 and 8). LOD6's 4x columns = far connector-shell repair (1.38 worker-s). No code committed: the diagnostic instrumentation stays uncommitted for L9. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01CSFYgsdW8ejZSyiMf4qRSX