Problem: WanVideoWrapper caches device at module load time, causing timesteps
and tensors to be created on wrong device when looping between models on
different GPUs.
Solution: WanVideoSamplerMultiGPU wrapper updates module-level device variable
to match current model's device before sampling.
Changes:
- Added comprehensive logging to trace device allocation through pipeline
- Identified module-level device caching as root cause
- Simplified WanVideoSamplerMultiGPU to only update device variable
- Verified fix works for multi-model workflows with looping
- Created custom implementations for all WanVideo nodes with explicit device selection
- Added WanVideoBlockSwap with dual device control (swap_device and model_offload_device)
- Created WanVideoModelLoader_TWO for multi-model workflows to avoid race conditions
- Discovered core ComfyUI bug: safetensors loader ignores device index (uses device.type instead of str(device))
- All wrapper nodes use runtime module patching to override WanVideoWrapper's cached device variables
- Extensive logging added for debugging device assignments
John Pollock