[diffusion] quant: add FLUX.1-dev modelopt nvfp4 support (#22672)

docs/diffusion/quantization.md

@@ -48,6 +48,27 @@ backend.
 | `nunchaku-svdq`  | Pre-quantized Nunchaku transformer weights, usually named `svdq-{int4\|fp4}_r{rank}-...`   | `--transformer-weights-path`                         | Model-specific support such as Qwen-Image, FLUX, and Z-Image | `nunchaku`                            | SGLang can infer precision and rank from the filename and supports both `int4` and `nvfp4`                            |
 | `msmodelslim`    | Pre-quantized msmodelslim transformer weights                                              | `--model-path`                                       | Wan2.2 family                                                | None                                  | Currently only compatible with the Ascend NPU family and supports both `w8a8` and `w4a4`                              |
 
+## Validated ModelOpt Checkpoints
+
+This section is the canonical support matrix for diffusion ModelOpt checkpoints
+that have been brought up and verified in SGLang.
+
+### FP8
+
+| Base Model | Validated Scope | HF DiT Weights | Notes |
+| --- | --- | --- | --- |
+| `black-forest-labs/FLUX.1-dev` | single-transformer override, deterministic latent/image comparison, H100 benchmark, torch-profiler trace | `BBuf/flux1-dev-modelopt-fp8-sglang-transformer` | SGLang converter keeps a validated BF16 fallback set for modulation and FF projection layers; use `--model-id FLUX.1-dev` for local mirrors |
+| `black-forest-labs/FLUX.2-dev` | single-transformer override load and generation path | `BBuf/flux2-dev-modelopt-fp8-sglang-transformer` | published SGLang-ready transformer override |
+| `Wan-AI/Wan2.2-T2V-A14B-Diffusers` | primary `transformer` quantized, `transformer_2` kept BF16 | `BBuf/wan22-t2v-a14b-modelopt-fp8-sglang-transformer` | do not describe this as dual-transformer full-model FP8 unless that path is validated separately |
+
+### NVFP4
+
+| Base Model | Validated Scope | HF DiT Weights | Notes |
+| --- | --- | --- | --- |
+| `black-forest-labs/FLUX.1-dev` | mixed BF16+NVFP4 transformer override, correctness validation, 4x RTX 5090 benchmark, torch-profiler trace | `unpublished` | use `build_modelopt_nvfp4_transformer.py`; validated builder keeps selected FLUX.1 modules in BF16 and sets `swap_weight_nibbles=false` |
+| `black-forest-labs/FLUX.2-dev` | packed-QKV load path | `black-forest-labs/FLUX.2-dev-NVFP4` | validated packed export detection and runtime layout handling |
+| `Wan-AI/Wan2.2-T2V-A14B-Diffusers` | primary `transformer` quantized with official ModelOpt FP4 export, `transformer_2` kept BF16 | `unpublished` | global `--transformer-weights-path` targets only the primary `transformer`; keep `transformer_2` on the base checkpoint unless you pass a per-component override; validated on B200 with `SGLANG_DIFFUSION_FLASHINFER_FP4_GEMM_BACKEND=cudnn` |
+
 ## ModelOpt FP8
 
 ### Usage Examples
@@ -83,7 +104,7 @@ sglang generate \
 - The layerwise offload path now preserves the non-contiguous FP8 weight stride
   expected by the runtime FP8 GEMM path.
 - To build the converted checkpoint yourself from a ModelOpt diffusers export,
-  use `python -m sglang.multimodal_gen.tools.convert_modelopt_fp8_checkpoint`.
+  use `python -m sglang.multimodal_gen.tools.build_modelopt_fp8_transformer`.
 
 ## NVFP4
 
@@ -110,10 +131,33 @@ sglang generate \
   --save-output
 ```
 
+For a dual-transformer Wan2.2 export where only the primary `transformer`
+was quantized:
+
+```bash
+SGLANG_DIFFUSION_FLASHINFER_FP4_GEMM_BACKEND=cudnn \
+sglang generate \
+  --model-path Wan-AI/Wan2.2-T2V-A14B-Diffusers \
+  --transformer-weights-path /path/to/wan22-nvfp4-export/transformer \
+  --prompt "a fox walking through neon rain" \
+  --save-output
+```
+
 ### Notes
 
 - `--transformer-weights-path` is still the canonical CLI for NVFP4
   transformer checkpoints.
+- For dual-transformer pipelines such as `Wan2.2-T2V-A14B-Diffusers`, the
+  global `--transformer-weights-path` applies only to the primary
+  `transformer`. Use a per-component override such as `--transformer-2-path`
+  only when you intentionally want a non-default `transformer_2`.
+- On Blackwell, the validated Wan2.2 ModelOpt NVFP4 path currently prefers
+  FlashInfer FP4 GEMM via
+  `SGLANG_DIFFUSION_FLASHINFER_FP4_GEMM_BACKEND=cudnn`.
+- This environment-variable override is a current workaround for NVFP4 cases
+  where the default sglang JIT/CUTLASS `sm100` path rejects a large-M shape at
+  `can_implement()`. The intended long-term fix is to add a validated CUTLASS
+  fallback for those shapes rather than rely on the override.
 - Direct `--model-path` loading is a compatibility path for FLUX.2 NVFP4-style
   repos or local directories.
 - If `--transformer-weights-path` is provided explicitly, it takes precedence