fix(VT-FP8-QUANT-ARCH-GATE): register QuantFp8Static from an unconditional CUDA TU (#960)

.agents/issue-index.md

@@ -265,3 +265,5 @@ rather than merged. `scripts/check-agent-record.py` gates both.
 | [#975](https://github.com/mudler/vllm.cpp/issues/975) | `LTX25-IC-LORA` | The reference-image / reference-video arm of `ltx-2.5` is still refused, and BOTH reasons the refusal ever gave are now false: the IC-LoRA metadata ([#923](https://github.com/mudler/vllm.cpp/issues/923) reads it at load, `iclora_utils.py:30-49`) and the token-APPEND machinery ([#930](https://github.com/mudler/vllm.cpp/issues/930) built it in `c7cb59fbb`; the LAST-frame keyframe is SERVED on it). Two causes remain. (1) The reference CLIP has no pixel path: upstream reads it at `height // scale` by `width // scale` (`iclora_utils.py:116-117`), refuses a target the factor does not divide (`:112-115`), keeps frame 0 then every Nth frame (`temporal_subsample`, `:87-89`, called at `:144`) and encodes the clip (`:145-148`), while this engine's only pixel-to-latent route encodes ONE frame at the phase's own resolution and nothing reads `ref_video_dir` (`src/vllm/multimodal/video_engine.cpp:375`). `Ltx2ConvVideoEncode` already takes a `frame_count`, so the encoder is not the gap. (2) The reference item is a STAGE-1 item and stage 2 must run UNFUSED: `ic_lora.py:108` gives stage 1 `loras=tuple(loras)` and the reference conditioning (`:269-278`, `:377-402`), `:119` gives stage 2 `loras=()` and `:314-321` gives it `combined_image_conditionings` with no reference item — and this engine holds ONE DiT, fused at load, that every phase runs. `Ltx2LatentState` having no attention-mask field is NOT the reason either: the default arm builds no mask (`iclora_utils.py:159-160`, `:168-169`). Listed under `## Owed` in [`ltx25-ic-lora.md`](specs/ltx25-ic-lora.md) | feature |
 | [#940](https://github.com/mudler/vllm.cpp/issues/940) | `MODEL-TEXT-nemotron-h-nemotron-hfor-causal-lm` | The FP8 W8A8 linear path is not a shared seam: `ResidentFp8`, `MatmulFp8CutlassD` and `MatmulFp8CutlassPreQuantD` lived in the anonymous namespace of `src/vllm/model_executor/models/qwen3_5.cpp` (`:1458`, `:1495`, `:1517` @ `c7cb59fbb`), so a second model could reach them only by copying them — the hand-rolled parallel path AGENTS.md §"Shared seams" forbids. NVFP4 already had `dense_nvfp4_gemm.h` + `compressed_tensors/schemes/nvfp4.h`; FP8 had neither half. Forced by `MODEL-NEMOTRON-H` ([#517](https://github.com/mudler/vllm.cpp/issues/517)), whose 46 FP8 W8A8 mamba `in_proj`/`out_proj` projections are 36.6% of decode bytes and 27.6% of GEMM FLOPs, and whose `in_proj` produces the fused `zxbcdt` the conv and the SSD scan consume — so that block cannot be split and has no device path at all without the seam. Extracted to `dense_fp8_gemm.h` + `quantization/fp8.h` with Qwen3.5 byte-identity as the gate; spec [`vt-fp8-shared-seam.md`](specs/vt-fp8-shared-seam.md) | bug |
 | [#974](https://github.com/mudler/vllm.cpp/issues/974) | — | The FP8 W8A8 resident helpers move weight bytes host->device without `vllm::load_stats::AddDeviceUpload` and without the post-upload `AdoptDeviceBytesAsHost`, while every other resident-weight helper in the same file performs both: `ResidentWeight` (`src/vllm/model_executor/models/qwen3_5.cpp:1009,1016 @ c7cb59fbb`) and `ResidentNvfp4` (`:1106,1111,1116,1121`), whose own comment states the obligation against [#150](https://github.com/mudler/vllm.cpp/issues/150). Affects `ResidentFp8` (`:1458`, now `dense_fp8_gemm.h`), `ResidentFp8Qkv` (`:1555`) and `ResidentFp8Qkvz` (`:3440`). Two unmeasured consequences: load accounting is short by the whole fp8 tower, and its device pages are never re-tagged, which is the shape of the GB10 weight-residency penalty on the 27B decode gap's largest attributed bucket. Found while extracting those entry points in [#940](https://github.com/mudler/vllm.cpp/issues/940) and deliberately NOT fixed there: a byte-identity gate cannot see a device -behaviour change hidden in a move. Listed under `## Owed` in [`vt-fp8-shared-seam.md`](specs/vt-fp8-shared-seam.md) | bug |
+| [#960](https://github.com/mudler/vllm.cpp/issues/960) | `MODEL-TEXT-nemotron-h-nemotron-hfor-causal-lm` | `vt::QuantFp8Static`'s ONLY CUDA registration lived at `src/vt/cuda/cuda_matmul_fp8_cutlass.cu:376` (@ `0e1bee42f`), and `CMakeLists.txt:1668` compiles that translation unit only when `VT_CUTLASS_FP8_ARCHS` is non-empty — yet the kernel body has ZERO cutlass tokens (`:353-370`): it is `out[i] = e4m3(x[i] * (1/input_scale))`, a grid-stride elementwise convert. So on every CUDA arch outside the cutlass-fp8 cell — sm_110/Thor is the measured one, and `cutlass-fp8: DISABLED for [110]` is that arch's DOCUMENTED NORMAL PROFILE, not a misconfiguration — `OpId::kQuantFp8Static` was not registered for `DeviceType::kCUDA` at all. Nothing refused first: the GEMM partner `kMatmulFp8CublasLt` IS registered unconditionally (`src/vt/cuda/cuda_matmul.cu:920`), so `MatmulFp8CutlassD`'s guard passed, and the missing quant then resolved through `src/vt/op_provider.cpp:501` to the portable CPU reference tier — eligible because `CudaBackend::UnifiedMemory()` is true — which dereferenced DEVICE pointers on the host and SIGSEGV'd one call later under a banner reading "correct but slow". Fixed by relocating the registration to a new unconditionally-compiled TU `src/vt/cuda/cuda_quant_fp8.cu`, which restores upstream's own partition (vLLM builds `static_scaled_fp8_quant` from the unconditional `VLLM_EXT_SRC` list and gates only its cutlass `scaled_mm` sources). This removes one live INSTANCE of [#844](https://github.com/mudler/vllm.cpp/issues/844) and does not address its class, which stays open. Unblocks the FP8 W8A8 arm on every non-cutlass CUDA arch — the base [#810](https://github.com/mudler/vllm.cpp/issues/810)/[#517](https://github.com/mudler/vllm.cpp/issues/517) A2-Q1 needs, where 46 FP8 mamba projections are 36.6% of decode bytes. Spec [`vt-fp8-quant-arch-gate.md`](specs/vt-fp8-quant-arch-gate.md) | bug |
+| [#989](https://github.com/mudler/vllm.cpp/issues/989) | `VT-FP8-QUANT-ARCH-GATE` | `scripts/check-pr-size.py`'s `classify_path` has no entry for `.agents/reachability.md` (added by `POLICY-NOTHING-LANDS-DEAD`, [#888](https://github.com/mudler/vllm.cpp/issues/888) @ `8f49ac3be`), and it FAILS CLOSED, so `pr-size` — a REQUIRED check — refuses every pull request that touches that guide, and `tests/scripts/test_check_pr_size.py` has been red on `main` ever since. Red SILENTLY: that suite is wired into no CI job and is not in `agent-preflight.sh`'s `SUITES`, so the only thing that ever loads it is `check-pr-size`'s own executable-evidence contract, which fires only when a PR edits a checker — the red is reachable exclusively by the next person who must touch that file, and presents to them as their own breakage (the [#584](https://github.com/mudler/vllm.cpp/issues/584)/[#965](https://github.com/mudler/vllm.cpp/issues/965) shape). Third instance of the class after [#856](https://github.com/mudler/vllm.cpp/issues/856) (`issue-index.md` + the style guides) and [#668](https://github.com/mudler/vllm.cpp/issues/668) (`.agents/oracles/*`), both fixed in flow by the row that tripped over them. FIXED IN FLOW while landing [#960](https://github.com/mudler/vllm.cpp/issues/960), which could not register its new checker's creation mutation without touching `check-pr-size.py` at all. NOT fixed: wiring that suite into CI, which is its own change and would red `main` until this landed | bug |