# L171 — UE arrival measurement

**Result:** Not measured. The A/A warm-up aborts before the first streaming sample, so this round cannot say whether L170’s +1.28% arrival difference exceeds UE noise or identify its cause.

Two `assembler/world` `ca0bf76` VFHost Development builds completed and produced identical VoxelForge, VoxelForgeCore, and VoxelForgeEditor binaries. With that matched module set staged, the A/A warm-up reaches `world_assembly_plan` with one surface stratum, then logs `surface_strates=858993460` after snapshot parsing and terminates with `std::length_error: vector` during `AVoxelWorld::BeginPlay`. The trace has no scheduler readback or streaming sample. This points to a Core snapshot/module compatibility failure; the exact cause is unproven.

Valid arrival pairs: A/A **0/15**, switches-on **0/15**, switches-off **0/15**. No medians, paired spread, or slower counts are available. The A/B batches were not started because the A/A control failed validation. Failed launches are logged under `Saved/Linux/l171/ue/arrival/`.

The baseline and L170 HEAD-off VFHost builds passed. The runner compiled and its CLI loaded; `git diff --check` passed. No Unreal `Source/` files changed. The full arrival matrix and fast verification did not run: the UE control never reached measurement.