ComfyUI LTXV2 SamplerCustomAdvanced - AttributeError: module 'torch' has no attribute 'float4_e2m1fn_x2'

[novice-101]

(posted originally in ComfyUI support:)

Both official and Kijai WF fail. Tried to save a bit on memory by going fp8 gemma and fp4 checkpoint.

Portable: .\python_embeded\python.exe -s ComfyUI\main.py --windows-standalone-build --cuda-malloc --reserve-vram 2.0 --use-sage-attention (tried without sage or cross attention, still fails)

Win11, 5070 Ti 16GB, 64GB RAM pytorch version: 2.7.0+cu128 Python version: 3.12.10 ComfyUI version: 0.8.0 ComfyUI frontend version: 1.35.9

ltx-2-19b-dev-fp4.safetensors gemma_3_12B_it_fp8_e4m3fn.safetensors

in the console there's a wall of text starting: "unet unexpected: ['audio_embeddin..."

END of log: File "D:\ComfyUI_windows_portable\python_embeded\Lib\site-packages\comfy_kitchen\tensor\base.py", line 346, in torch_dispatch return op_handlers[parent_cls](qt, args, kwargs) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "D:\ComfyUI_windows_portable\python_embeded\Lib\site-packages\comfy_kitchen\tensor\nvfp4.py", line 246, in handle_nvfp4_linear result = ck.scaled_mm_nvfp4( ^^^^^^^^^^^^^^^^^^^ File "D:\ComfyUI_windows_portable\python_embeded\Lib\site-packages\comfy_kitchen_init.py", line 160, in scaled_mm_nvfp4 return torch.ops.comfy_kitchen.scaled_mm_nvfp4( ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "D:\ComfyUI_windows_portable\python_embeded\Lib\site-packages\torch_ops.py", line 1158, in call return self._op(*args, **(kwargs or {})) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "D:\ComfyUI_windows_portable\python_embeded\Lib\site-packages\torch_library\custom_ops.py", line 335, in backend_impl result = self._backend_fns[device_type](*args, **kwargs) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "D:\ComfyUI_windows_portable\python_embeded\Lib\site-packages\torch_compile.py", line 51, in inner return disable_fn(*args, **kwargs) ^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "D:\ComfyUI_windows_portable\python_embeded\Lib\site-packages\torch_dynamo\eval_frame.py", line 838, in _fn return fn(*args, **kwargs) ^^^^^^^^^^^^^^^^^^^ File "D:\ComfyUI_windows_portable\python_embeded\Lib\site-packages\torch_library\custom_ops.py", line 367, in wrapped_fn return fn(*args, **kwargs) ^^^^^^^^^^^^^^^^^^^ File "D:\ComfyUI_windows_portable\python_embeded\Lib\site-packages\comfy_kitchen\backends\eager\quantization.py", line 379, in op_scaled_mm_nvfp4 return impl(**kwargs) ^^^^^^^^^^^^^^ File "D:\ComfyUI_windows_portable\python_embeded\Lib\site-packages\comfy_kitchen\backends\eager\quantization.py", line 178, in scaled_mm_nvfp4 a.view(torch.float4_e2m1fn_x2), ^^^^^^^^^^^^^^^^^^^^^^ File "D:\ComfyUI_windows_portable\python_embeded\Lib\site-packages\torch_init.py", line 2688, in getattr raise AttributeError(f"module '{name}' has no attribute '{name}'") AttributeError: module 'torch' has no attribute 'float4_e2m1fn_x2'