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Reflection AI's Beam 1.0 ranks #12 among open models on Agent Arena

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Arena says Reflection AI's Beam-1.0-501B-A23B ranks #12 among open-weight models on Agent Arena, with a -3.67% Net Improvement. It ranks #22 among open models on Code Arena: WebDev with 1438 points and is released under Apache 2.0. Arena notes a ±3.84% margin of error on Net Improvement, placing Beam closer to the two Qwen3.8 models above it than its rank suggests.

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The post reports Beam's rank among open models on two Arena leaderboards, alongside the margin of error that limits how far that rank can be read.

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Exciting news: Beam-1.0-501B-A23B by @Reflection_AI just landed #12 among open weight models in Agent Arena with -3.67% Net Improvement, and #22 among open in Code Arena: WebDev with 1438 pts. It’s also fully open under Apache 2.0.

On the Agent Arena leaderboard, Beam 1.0 is the top-ranked US model among open models, landing at #12. That puts it ahead of Hy3, MiMo V2.5 Pro and MiniMax M3. Its margin of error is wide (±3.84% on Net Improvement), so it’s statistically closer to the two Qwen3.8 models just above it than its rank suggests.

On Code Arena: WebDev, 24 of the top 25 open models come from Chinese labs. The one exception is Reflection’s Beam 1.0 (Apache 2.0). It ranks #22 among open models, which makes it the top US open model on the board, just ahead of Kimi K2.5 Thinking and GLM-5.

Congrats to the @Reflection_AI team on this solid open weights release!

Reflection@reflection_ai
Introducing Beam: a highly efficient agentic open model with 501B total parameters and 23B active. - Frontier reasoning efficiency - Advances the Western open frontier on coding & agentic tasks - Trained end-to-end from scratch Full weights release this month. Learn more about Beam: http://reflection.ai/beam
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