Initialize does StrateLayout.Empty() and Passages.Empty()/Add() -- freeing and
reallocating both -- with no guard, while mesher workers read them through
AnyPassageNearBox, EvaluateModifierSDF and FindSlotIndexForChunkZ. The epoch is
bumped AFTER, so previous-epoch workers are live during the mutation; the epoch
rejects a finished result, it cannot make a read of a freed allocation safe.
Same class as the DiffLayer.ChunkMods carve-vs-stream AV that ModsLock fixed.
Chose the drain over the two alternatives:
- FRWLock on the arrays: correct, exact in-repo precedent, but a read lock on
the per-voxel hot path (~43k/tile) would contaminate the perf measurement
CODEX-TASK-001/002 are queued to take. Worst possible timing.
- Immutable generation snapshot (Sol's proposal): right long-term, refactors
the whole StrateManager API surface. A design conversation, not an agent's
unprompted call.
- Drain: zero hot-path cost, reuses the machinery EndPlay already proved, and
its stall lands only on human-initiated editor actions, never during play.
FScopedGenerationPause raises a new bGenerationPaused (deliberately NOT
bShuttingDown, which means teardown) and drains both reader populations: chunk
tasks via ActiveTaskCount and decoration tasks via a new
WaitForDecorationTasks, whose refactor also removed NotifyShutdown's duplicate
spin loop. On timeout it does NOT mutate -- logs an Error and leaves the world
consistent. A timeout that proceeds is what the bug already does.
RebuildStrates, OnObjectModifiedInEditor and ChangeSeed cannot reach Initialize
without the pause. BeginPlay untouched (no tasks yet). EndPlay untouched --
VF-02's 3s timeout is a separate deliberate decision.
Verified: four files, no density/mesher file, so terrain cannot move.
ShouldAbortWork replaced three existing checks, adding none. No worker path
waits on the game thread, so the drain is bounded.
Not built -- Jahni builds.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
