Beam: Reflection's 501B open-weight model

What changed

We are introducing Beam, Reflection’s first open-weight model. Beam is a sparse Mixture-of-Experts model with 501 billion total parameters, 23 billion active, built for coding, reasoning, and agentic workloads. We will be launching Beam with an ecosystem of distribution partners, as well as integration with a broad range of open source libraries and harnesses, so developers can use Beam across existing open-source workflows.

Why it matters

A concrete addition to Practical AI: Tools, Models & Frameworks: it changes what's available to builders today rather than being general commentary.

How it compares

Related prior coverage to compare against:

• Reflection debuts Beam, an open-weight AI model to rival Chinese models at lower compute cost
• Clef: Open-weight decision models, and new RL fine-tuning platform
• GLM-5.3 is now open-weight

• Reflection debuts Beam, an open-weight AI model to rival Chinese models at lower compute cost similarity 0.41
• Clef: Open-weight decision models, and new RL fine-tuning platform similarity 0.38
• GLM-5.3 is now open-weight similarity 0.38