Via upstage.ai
The South Korean AI startup tripled its flagship model's intelligence score while targeting enterprise workflows that demand deep reasoning and massive context windows.
Upstage’s latest reasoning model, Solar Pro 4, just landed with a score of 42 on the Artificial Analysis Intelligence Index. For context, its predecessor, Solar Pro 3, scored 14. That’s a 3x jump in a single generation.
The South Korean AI startup, founded in 2020, is positioning Solar Pro 4 as a purpose-built tool for enterprise environments drowning in documents, multi-step workflows, and complex reasoning tasks.
The numbers behind the upgrade #
Solar Pro 4’s benchmark performance tells a story of broad improvement rather than a single flashy headline number. On Terminal-Bench v2.1, a test designed to evaluate agentic task execution, the model scored 57%. Its long-context reasoning score (AA-LCR) hit 71%, reflecting better performance when processing lengthy documents. Multi-turn tool use, measured by the τ³-Banking benchmark, came in at 23%.
The most eye-catching figure might be the GDPval-AA v2 Elo rating for real-world work tasks: 1,277. The human baseline on that same evaluation sits at 1,000, meaning Solar Pro 4 is measurably outperforming the average human worker on the specific task categories being tested.
The model supports a context window of roughly 524K tokens. Solar Pro 4 also includes what Upstage calls a “reasoning-effort dial,” letting users balance depth of analysis against speed. Solar Pro 4 takes an average of 8.6 minutes per Intelligence Index task, compared to 6.0 minutes for Pro 3.
Solar Pro 4 reportedly handles hallucinations better by simply abstaining from generating a response when it lacks sufficient evidence.
Aggressive pricing and distribution #
Upstage launched Solar Pro 4 with a promotional discount of 90% on API pricing, running until September 10, 2026. During the promotional window, input tokens cost $0.30 per million and output tokens run $1.20 per million.
The model is available through Upstage’s own API, OpenRouter, and through Nous Research’s Hermes Agent platform.
The language support is also worth noting: English, Korean, and Japanese.
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