vLLM adds day-0 support for Reflection's 501B Beam model with Blackwell optimizations
vLLM published day-0 serving support for Reflection's Beam, a 501B-parameter mixture-of-experts model with 23B active parameters per token, optimized for NVIDIA Blackwell. The engine handles reasoning, tool calling and structured outputs out of the box and can run Beam with tensor, data or expert parallelism, with a Docker image and launch command provided. The post says coding agents autonomously tuned the implementation so batch-1 decode is 2.71× faster and prefill 1.87× faster than the first version, and that Beam's DFlash2 drafter reaches 708 tokens/s for a single request on TP8 with an acceptance length of 3.7. It also describes day-0 reinforcement-learning support built with the SkyRL team, reporting AIME25 average accuracy rising from about 61% to about 79% after 50 training steps.
For teams self-hosting large open-weight MoE models, the post says Beam can be served on vLLM from launch day with reasoning, tool-calling and Blackwell kernel optimizations, plus a SkyRL reinforcement-learning path.
TL;DR: Reflection's Beam is a 501B-parameter MoE with 23B active parameters per token. vLLM supports it from day 0 and optimizes it on NVIDIA Blackwell:
- Full feature support. Reasoning, tool calling, and structured outputs work out of the box, and you can run the model with tensor, data, or expert parallelism.
- Agent-driven optimization. Coding agents optimized the model autonomously, making batch-1 decode 2.71× faster and prefill 1.87× faster than our first implementation.
- DFlash2 with adaptive verification. With Beam's DFlash2 drafter, a single request reaches 708 tokens/s on TP8, with an acceptance length of 3.7. Adaptive verification, which decides each step how many draft tokens are worth verifying, adds 10% more throughput at high concurrency.
To try it, use our Docker image vllm/vllm-openai:reflection-beam:
docker run --gpus all --ipc=host -p 8000:8000 \
-v ~/.cache/huggingface:/root/.cache/huggingface \
vllm/vllm-openai:reflection-beam \
reflection/Beam-1.0-501B-A23B-NVFP4 \
-tp 4 \
--max-num-seqs 128 \
--reasoning-parser beam \
--tool-call-parser beam --enable-auto-tool-choice \
--kv-cache-dtype fp8 \
--attention-config '{"backend":"FLASHINFER"}' \
--kernel-config '{"enable_flashinfer_autotune":false}' \
--speculative-config '{
"method": "dflash",
"model": "reflection/Beam-1.0-501B-A23B-DFlash2",
"num_speculative_tokens": 7,
"attention_backend": "FLASH_ATTN"
}'#Reflection#Beam#vLLM#NVIDIA#Inferact#SkyRL#Blackwell#GB300#FlashInfer#DeepSeek-V3