Reflection AI open-sources Beam-1.0-501B-A23B, ranked 12th on the Agent Arena open-source leaderboard
Reflection AI has released the open-source model Beam-1.0-501B-A23B under the Apache 2.0 license. It ranks 12th among open-weight models on Agent Arena with a Net Improvement of -3.67%, and ranks 22nd on the Code Arena: WebDev open-source leaderboard with a score of 1438. On the Agent Arena leaderboard it is the highest-ranked US open-source model, ahead of Hy3, MiMo V2.5 Pro and MiniMax M3, but its Net Improvement error margin reaches ±3.84%, making it statistically closer to the two Qwen3.8 models above it. Of the top 25 open-source models on Code Arena: WebDev, 24 come from Chinese labs; Beam 1.0 is the only exception and the highest-ranked US open-source model on that leaderboard, slightly ahead of Kimi K2.5 Thinking and GLM-5.
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Beam 1.0's rankings and error margins on Agent Arena and Code Arena show where US open-source models stand on leaderboards dominated by Chinese models.
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View original postIntroducing 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: https://t.co/c3Qx2cpM8G
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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: https://t.co/c3Qx2cpM8G
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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!