AI Coding Live News — Real-Time 𝕏/Twitter Updates & Breakthroughs

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Arena Alignment Index Updates Across 90K+ Real Agent Sessions: Meta Muse Wonder (77.5%), Reflection Beam-1.0 (75.3%), and StepFun Step 5 Preview (75.1%) Debut

Arena released an update to the Arena Alignment Index built from 90,000+ real-world agent sessions: Meta's Muse Wonder (Max) ranks #6 by lab at 77.5% (2.09% unauthorized action rate, 14.41% deceptive completion rate), Reflection AI's open-weight Beam-1.0-501B-A23B debuts at #7 with 75.3% (4.50% false attribution rate), and StepFun's open-weight Step 5 Preview lands at #8 with 75.1% (2.11% unauthorized action rate).

Key Takeaways

Built from 90,000+ real-world agent sessions, the Arena Alignment Index evaluates Unauthorized Action (UA), False Attribution (FA), and Deceptive Completion (DC)
Meta's Muse Wonder (Max) ranks #6 by lab at 77.5%, posting the lowest unauthorized action rate (2.09%) and deceptive completion rate (14.41%) of the new cohort
Reflection AI's Beam-1.0-501B-A23B (#1 US open model on Agent Arena) debuts at #7 with 75.3% and leads the newcomers with a 4.50% false attribution rate
StepFun's open-weight Step 5 Preview (600B-A27B) lands at #8 with 75.1% and a 2.11% unauthorized action rate, nearly matching Muse Wonder

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Linked Models & Agents:

#Arena#Alignment Index#Muse Wonder#Reflection AI#Step 5 Preview#Agent Safety

ModelScope@ModelScope2022·Collected 22d ago

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StepFun opens Step 5 Preview weights: 600B/27B sparse MoE agent flagship with 1M context now on Hugging Face and ModelScope

On 2026-10-15 StepFun released open weights for Step 5 Preview as promised: a 600B-total / 27B-active sparse MoE with up to 1M-token context and vision input, aimed at agentic software engineering and knowledge work. Checkpoints are on Hugging Face (FP8, BF16, NVFP4) and ModelScope. Official scores include StepCodeBench 49.0%, FrontierFinance 66.4%, and Artificial Analysis Intelligence Index 44. September coverage was API/index only; this is the first public weight drop.

Key Takeaways

Specs: sparse MoE 600B total / 27B active, up to 1M-token context, text+image input (model page)
Weights: stepfun-ai/Step-5-Preview plus BF16 and NVFP4 on Hugging Face and ModelScope (HF card)
Coding: StepCodeBench avg@4 49.0% (leads the open-weight set StepFun cites); DeepSWE v1.1 67.7% (official table)
Finance / index: FrontierFinance 66.4%; Artificial Analysis Intelligence Index 44 (matches earlier AA coverage)
Serve via official vLLM / SGLang Docker images and OpenAI-compatible APIs; license is StepFun Model License 1.0 (Apache-2.0-style with commercial conditions)

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Linked Models & Agents:

⚡ Step 5 Preview🌐 stepfun 🌐 modelscope 🌐 huggingface

#StepFun#Step 5 Preview#MoE#Agents#1M context#Hugging Face#ModelScope

Artificial Analysis@ArtificialAnlys·Collected 45d ago

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Artificial Analysis: StepFun Step 5 Preview scores 44 on Intelligence Index at ~2.8x lower cost than Kimi K3

@ArtificialAnlys evaluated StepFun Step 5 Preview (600B-total / 27B-active MoE): Artificial Analysis Intelligence Index 44, matching Kimi K3 (max) at about $0.72 per Index task (~2.8x cheaper). Pricing is about $1/$2.70 per 1M input/output tokens with $0.05/M cached input; 1M context; open weights planned for October 15. It still lags peers on agentic evals such as GDPval-AA and Terminal-Bench 4.0.

Key Takeaways

AA Intelligence Index 44, tied with Kimi K3 (max); ~$0.72/task (~2.8x cheaper).
Pricing ~$1/$2.70 per 1M in/out with $0.05/M cached input; 600B/27B MoE; 1M context.
Open weights planned Oct 15; still trails peers on GDPval-AA and Terminal-Bench 4.0.

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Linked Models & Agents:

⚡ Stepfun Step 5 Preview⚡ Kimi K3

#Step 5 Preview#StepFun#Artificial Analysis#Intelligence Index#MoE#Pricing#open weights