Upstage Releases Solar Pro 4 With 524K Token Context Window at $0.03/M Input Pricing

Upstage has released Solar Pro 4, a new large language model with a 524,000 token context window, according to a listing on OpenRouter where the model is now available as upstage/solar-pro4.

The model is positioned by Upstage for agentic workflows, office productivity tasks, document-intensive work, and coding. It operates in text-to-text mode only, with no stated support for image, audio, or video inputs.

Pricing and Access

Solar Pro 4 is priced at $0.03 per million input tokens and $0.12 per million output tokens through OpenRouter's API. That places it among the lower-cost options in its context-window class, though independent benchmark results comparing it to competing models have not yet been published.

The 524K token context window is large enough to process lengthy documents, multi-file codebases, or extended multi-turn agentic sessions in a single call, which aligns with Upstage's stated target use cases of document processing and agentic workflows.

What We Don't Know

Upstage has not disclosed the model's parameter count, training data cutoff date, or architecture details in the material accompanying this release. No independent benchmark scores (MMLU, HumanEval, or similar standard evaluations) have been published alongside the launch, so claims about the model's suitability for coding and office productivity tasks remain Upstage's own characterization rather than independently verified performance data.

What This Means

Solar Pro 4 enters a market where long-context, low-cost models are increasingly common, and Upstage's pricing—$0.03/$0.12 per million tokens—undercuts many rivals offering comparable context lengths. The 524K token window is notable because it exceeds the context windows offered by several widely used commercial models, making it a candidate for teams processing large document sets or running extended agent sessions without chunking content.

However, without published benchmark results, buyers evaluating Solar Pro 4 for coding or reasoning-heavy tasks will need to run their own evaluations before committing production workloads to the model. Upstage, a South Korean AI company known for its Solar model family, appears to be competing primarily on context length and price rather than on demonstrated benchmark leadership at this stage. As with any newly released model lacking third-party verification, enterprises should treat throughput, latency, and accuracy claims as provisional until independent testing confirms them.