Reflection AI unveils Beam, a 501B-parameter open model due this month

Reflection AI has unveiled Beam, an open-weight AI model with 501 billion total parameters. The full release is expected later this month. The company announced the model on October 5, 2026. It is pitching Beam as a Western answer to the Chinese open models that have quietly taken over a big slice of developer workloads. What Beam actually is The technical name for this design is a sparse Mixture-of-Experts architecture. Beam has 501 billion parameters in total, but only 23 billion are active for any given token. A token is roughly a word or a chunk of a word. That gap matters because active parameters drive the cost of running a model. A huge model that only uses a small fraction of itself at a time can stay smart without burning cash on every reply. Reflection says Beam was pretrained on 23.8 trillion tokens. It then went through large-scale reinforcement learning, a process where the model practices tasks and gets rewarded for good answers. The company ran more than 100 million of these practice rollouts on 10.5K NVIDIA GB300 GPUs. The benchmark pitch Reflection is positioning Beam against two specific Chinese rivals: Z.ai’s GLM-5.2 and Alibaba’s Qwen 3.8-Max. According to the c...