SP4 Delivers the Behavioral Reliability Production Agents Require at a Fraction of Frontier-Model Cost — Surpassing 80 Billion Tokens in Three Days on OpenRouter

SAN JOSE, Calif., Aug. 20, 2026 /PRNewswire/ — Upstage AI, an enterprise AI company, announced the launch of Solar Pro 4 (SP4), its closed commercial flagship LLM on August 11. SP4 delivers the agent reliability enterprises need at a fraction of frontier-model cost. It is optimized for stably performing workflows, such as document understanding, information extraction, long-context reasoning, and continuous decision-making, capabilities that are critical for production environments and cost control at enterprise scale.

Upstage built Solar Pro 4 around behavioral reliability: the quality that determines whether agents actually work in production. Enterprises have exhausted annual AI budgets in months as agents burn tokens on retries, malformed outputs, and instruction-following failures. SP4 is engineered to prevent this waste: instruction following that holds across turns, tool call structure that stays intact, and agents that act as instructed, within policy, and in valid schema.

Market reception has been immediate. Within a week of being listed on OpenRouter, Solar Pro 4’s token consumption exceeded 370 billion tokens, driven by rapid global developer adoption. SP4 is also integrated into Hermes Agent, the AI agent developed by U.S.-based Nous Research, where it powers multi-step, self-improving AI agents for a global developer community. With these listings, Upstage is formally registered as a provider alongside OpenAI, Anthropic, Google, and Nvidia, placing Solar Pro 4 in direct daily comparison with the most widely used models in the world.

Solar Pro 4’s overall performance, based on the global AI evaluation body Artificial Analysis, is 42 points, placing it on par with general-purpose frontier models. This is an improvement of more than 3 times compared to the previous version. It surpassed big tech models like Nvidia’s Nemotron 3 Ultra (38 points) and Google’s Gemini 3.5 Flash-Light (37 points), and significantly outperformed competing sovereign models such as Mistral Medium 3.5 (30 points) and Cohere Command A+ (23 points).

The ability to handle long and complex documents without failure is a key strength. Solar Pro 4 scored 71 points in the long-context comprehension benchmark (AA-LCR), which assesses the ability to extract information from large volumes of long documents and infer answers based on that information, showing performance 2.3 times superior to the previous version. The reduction in failures where context is lost mid-document not only improves accuracy but also reduces token consumption, which is advantageous for operational costs.

“Enterprise AI buyers have been asking for a model optimized for what actually matters in production: agents that follow instructions, keep tool calls intact, and don’t burn budget on retries,” said Kasey Roh, Head of US of Upstage AI. “That’s what we built Solar Pro 4 to be, and eighty billion tokens in the first three days says the market agrees.”

“Businesses need AI to work practically, not just score well on tests,” said Sung Kim, CEO of Upstage AI. “Solar Pro 4 standing alongside the world’s leading models on global developer platforms, as the first model from Korea to do so, is proof that our technology works at global scale.”

The launch of SP4 follows Upstage’s release of Solar Open 2, the company’s open ecosystem.

Upstage built its core business serving major global enterprises in regulated and complex industries, such as financial services, insurance, manufacturing, and supply chain, where models must behave predictably in production, because enterprise deployments fail on inconsistency long before they fail on intelligence.

In the last few years, Upstage AI has built momentum as a global enterprise AI leader through the expansion of its Solar large language models, advancements in Document AI, strategic partnerships with AWS and AMD, and new investments supporting its international growth. Headquartered in South Korea, the company launched its US headquarters in 2025 and has been recognized among the world’s most innovative AI startups, reflecting its growing impact across enterprise and regulated industries.

About Upstage

Upstage is building the future of enterprise AI through language models and document AI engineered for production reliability. Its Solar family of large language models and Upstage Studio, its document AI platform, power workflows in  insurance, financial services, manufacturing, and other regulated industries, where accuracy, consistency, and cost control determine whether AI deployments succeed. Upstage is headquartered in South Korea with US headquarters in San Jose. For more information, visit upstage.ai.

For more information visit https://www.upstage.ai or contact them here.

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SOURCE Upstage AI