Welcome Beam: a 501B open model you can own, customize, and scale

Why it matters

Reflection has released Beam, an open-source large language model aimed at coding and agentic work, and made it available under a permissive Apache license. The model is a sparse mixture-of-experts design, meaning each token is processed by only a small slice of the network, which lets it run with the speed of a much smaller model while retaining the capacity of a large one. It handles very long contexts and offers adjustable reasoning effort, tool calling, and speculative decoding with DFlash2. Day-zero support in major inference libraries, along with recipes for inference and post-training, lowers the barrier for teams that want to run and customize a frontier-scale model on their own infrastructure. Reflection is encouraging community adoption by awarding Hub credits to the best projects built with the model. The release matters because it gives organizations a way to own and tailor a capable model rather than depend on closed, hosted alternatives, and its technical choices around attention, routing, and residual scaling show deliberate engineering for efficient long-context deployment.