[Arkex-ai]

Mapped texture staging is not required to be coherent, but the ASTC gather and CPU-converted upload paths did not flush their writes before GPU reads. A separate CPU/device-cache fixture reproduces stale submitted bytes on the noncoherent path while the coherent control passes.

This publishes each completed staging slice using its VMA allocation and allocation-relative offset/size. Slice starts also respect nonCoherentAtomSize, so a rounded flush does not share an atom with another slice already consumed by a parallel segment. CPU publication follows conversion-worker joins; ASTC publication follows layer gathering, before decoder commands. Arena lifetime, allocation policy, upload routing, format conversions and the renderer ABI are unchanged; no additional queue wait is introduced.

Validation at 62aa0079c82b5ad73f3fb0284d6a1f1c0811cf8d, based on main 1a429f6a84e3dd53fd4304e85abd0356da4164ca. The fixture uses its own namespace for native Windows CRT compatibility; no assertions or compiler warnings are disabled.

• 14 game-free coherent/noncoherent cases pass Windows LLVM, Linux GCC and GCC ASan/UBSan. They execute actual staging, the allocation-range helper, ASTC gather/publication prefix and CPU publication/copy-description region. Full CPU converters and decoder shaders are outside this fixture.
• Six behavioral mutations are rejected: omitted ASTC/CPU publication, wrong offset, partial range, shared atoms and lost allocation ownership.
• Full Windows suite: 239 passed / 2 failed / 20 skipped, versus current main 238 / 2 / 20. Both have the same local NUP symlink-privilege and missing-Windows-SDK precompile-guard failures.
• Official API12 standalone host/backend build succeeds using a fresh official guest generation on this main after its host/lifter changes. No generated game source is edited.
• Exact-head isolated native serial and parallel/batch checkpoint runs with FG2x both exit0, produce valid3440x1440 captures and survive maximize/restore. Original saves/settings are preserved.
• Exact-head fork CI: source regressions, Windows builder, and Linux AppImage all succeeded. Fork checks do not replace upstream review/required checks.

Limits: this is an authored cache-model reproduction, not a physical noncoherent GPU reproduction, performance measurement or campaign test. Earlier forced CPU/RGBA8 runs at 4cd6911 showed missing textures; an official unmodified d448ccc build reproduced missing textures under the same forced configuration. That comparison is recorded as an existing visual limitation, not a healthy CPU visual pass or pixel equivalence, and is not relabeled as current-head runtime evidence. Current-head native smoke uses default texture routing.

Overlap checked by actual diff/head: #1514 owns small-arena fallback and mapless rollback, #1541 adds staging diagnostics, and #1130 partitions ASTC uploads. This change preserves those separate behaviors. No game files, generated game code, binaries, saves or private runtime artifacts are included.