Task 10 (commit 0cbef3c) called ApplyCacheHit inside the per-(entity, partIdx)
foreach loop, but cachedEntry.Batches is flat across all MeshRefs of the
entity. For a 3-MeshRef static building on frame 2: 3 tuples times 6 cached
batches per call = 18 instances drawn instead of 6. Severe Z-fighting and
3x perf hit on every multi-part static entity (buildings, statues, multi-
MeshRef NPCs).
This is the symmetric mirror of the Task 9 bug fixed at 00fa8ae. Both
spec section 5.2 and the plan describe the foreach as per-entity, but
_walkScratch has been per-tuple since Task 6. The implementation
faithfully ported the buggy spec.
Fix: track lastHitEntityId; the cache-hit fast path fires only on the
first tuple of each entity, and subsequent tuples skip the iteration
body via continue. Adds a regression test pinning the per-entity
amplification invariant.
Caught by code review (subagent-driven-development) before Phase 3
dispatched. The bug was invisible in the no-multi-frame-test 1702/8
baseline; would have manifested as visible Z-fighting on every multi-
part building on second-and-subsequent frames once Task 13 perf gate
captured live runs.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
f7e38c214d