PyTorch 2.13 was released on July 8, 2026, with 526 contributors combining to submit 3328 commits. FlexAttention officially lands on Apple Silicon (MPS backend), with hand-written Metal kernels covering sparse prefill and decode. On 1×8×32768×64 long sequences + 256 sliding window (0.8% density) sparse mode, it gets about 12.3× speedup over SDPA; in the 8192/64 window scenario it still gets about 4.15×; the CUDA-side Flash backend adds a deterministic backward path, replacing atomic with precomputed write order, achieving bit-for-bit reproducibility with only +0.2% end-to-end overhead on long sequences. The new nn.LinearCrossEntropyLoss fuses the linear layer and cross-entropy into a single operator, streaming computation in chunks along the vocabulary dimension, cutting peak training memory for large-vocabulary LLMs by up to 4×. The CuTeDSL "Native DSL" backend provides CUTLASS-grade GEMM/RMSNorm code generation for Inductor; torchcomms replaces c10d, and FSDP2 supports overlapping reduce-scatter and all-gather communication. ExecuTorch is officially merged into PyTorch Core, making on-device inference a first-class citizen.