With intermediates following the output stem, concurrent wwstage-driver builds no longer share paths - 950/990-997 join the xargs -P group. Measured: 202.7s -> 153.8s full-test wall (x2 runs race-clean); the serial tail (57.7% of wall) is gone, remainder is CPU-bound. CLAUDE.md rule 14 documents the new reality: NNN range no longer a correctness constraint, still keys phase membership / skip set / cache set.