PyTorch 2.15 Release Blog

PyTorch 2.15 makes the rewritten NCCL backend the default for all nccl process groups, with a flight recorder that dumps diagnostics on hangs and TORCH_DIST_USE_NCCL2=0 or nccl-legacy as rollback paths. It adds one-sided transports for torch.distributed with a NIXL backend, finer FSDP2 and pipeline parallelism memory and communication controls, NVFP4 decode improvements on Blackwell, FP8 and faster decode on Apple Silicon, and broader platform support including FlyDSL on AMD gfx950, ROCm 10.0 wheels, CUDA 13.2 as the default wheel, and torch.compile on Python 3.15. The release contains 3,117 commits from 583 contributors since 2.14, and Python 3.10 and macOS 14 are no longer supported.