Short answer: Later in October 2026. Reflection AI announced Beam, its first open-weight model, on October 5, 2026, and said it will release the weights, technical report, model card, and developer files later this month. Until then, Beam is in final red-teaming and evaluation, and developers can sign up for early access.
Beam is a text-only sparse mixture-of-experts model with 501 billion total parameters, of which 23 billion are active for each token. Reflection says it was pretrained on 23.8 trillion tokens and is built mainly for coding, reasoning, and agentic tasks. The company claims it scores close to Z.ai’s GLM-5.2 on advanced reasoning benchmarks while using three to four times less inference compute; those results have not yet been independently verified.
Source: Reflection: Introducing Beam, Reflection’s 501B open-weight model
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