Add safetensors checkpoint loading support - #599
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All four checkpoint-loading paths (build_sam3_video_model, build_sam3_multiplex_video_model, build_sam3_multiplex_video_predictor, and the internal _load_checkpoint helper) now detect a .safetensors extension and use safetensors.torch.load_file instead of torch.load. The official Comfy-Org/sam3.1 HuggingFace distribution ships sam3.1_multiplex_fp16.safetensors; torch.load fails on this format with "unsupported pickle protocol: 104" (the safetensors magic bytes are misread as a pickle header). .pt / .pth checkpoints continue to use torch.load, now with weights_only=False so that legacy checkpoints using older pickle protocols still load without raising UnpicklingError.
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Summary
All four checkpoint-loading paths now detect a
.safetensorsextension and usesafetensors.torch.load_fileinstead oftorch.load:_load_checkpointhelperbuild_sam3_video_modelbuild_sam3_multiplex_video_modelbuild_sam3_multiplex_video_predictorMotivation
The official Comfy-Org/sam3.1 HuggingFace distribution ships
sam3.1_multiplex_fp16.safetensors. Passing this file to any of the above builders fails with:The safetensors magic bytes are misread as a legacy pickle header by
torch.load..pt/.pthcheckpoints continue to usetorch.load, now withweights_only=Falseso that legacy checkpoints using older pickle protocols still load without raisingUnpicklingError.Test plan
sam3.1_multiplex_fp16.safetensorsviabuild_sam3_multiplex_video_model— previously crashed, now loads correctly.ptcheckpoint viabuild_sam3_video_model— still loads correctly withweights_only=False