Beam: Reflection's 501B open-weight model

Open weights are getting genuinely large. Beam is a 501B-parameter sparse MoE with 23B active, Apache 2.0, 1M context, and 80.9 on SWE-Bench Verified. The training footnote I enjoyed most: over 100 million RL rollouts on 10,500 GB300s in four weeks. Reflection claims reasoning comparable to GLM-5.2 at 3-4x less inference compute. Weights are promised this month, which is the bit that actually matters if you self-host.