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v0.21.0

Highlights This release features 367 commits from 202 contributors (49 new)! Transformers v4 deprecated : This release formally deprecates transformers v4 support ( #40389 ). Users should migrate to transformers v5. C++20 build requirement : vLLM now requires a C++20-compatible compiler for compatibility with PyTorch ( #40380 ). This is a breaking build change . KV Offload + Hybrid Memory Allocator (HMA) : The KV offloading subsystem now integrates with the Hybrid Memory Allocator, including scheduler-side sliding window group support and full HMA enablement ( #41228 , #41445 , #39571 ). Speculative decoding with thinking budget : Speculative decoding now respects reasoning/thinking budgets, enabling correct spec decode for reasoning models ( #34668 ). TOKENSPEED_MLA backend on Blackwell : A new TOKENSPEED_MLA attention backend is available for DeepSeek-R1/Kimi-K25 prefill + decode on Blackwell GPUs ( #41778 ). Model Support New architectures: MiMo-V2.5 ( #40967 ), Laguna XS.2 ( #41129 , #41880 ), Moondream3 ( #32325 ), Qianfan-OCR ( #40136 ), Cohere MoE ( #40817 ), Cohere Eagle ( #42078 ). Speculative decoding: EAGLE for Mistral ( #41024 ), Gemma4 MTP ( #41745 ), MTP for MiMo-V2.5 ( #41905 ), Cohere Eagle ( #42078 ). DeepSeek V4: AMD/ROCm support ( #40871 ), pipeline parallelism ( #41694 ), max reasoning effort ( #40982 ), disaggregated serving fixes ( #41957 ). Tool calling: Cohere reasoning and tool parsers ( #40422 ), LFM2/2.5 tool parser ( #39243 ). Gemma3/Gemma4: hidden