Upstage launches Solar Pro 4 for multi-step agent work
Solar Pro 4 supports tool use, terminal tasks and long-document reasoning, with a 512K-token context window and multilingual input and output.
Quick answer
What did Upstage announce with Solar Pro 4?
Upstage launched Solar Pro 4, an API-accessible model designed for multi-step agent work involving documents, tools and terminal tasks. The company says it supports a 512K-token context window, produces up to 128K output tokens, handles English, Korean and Japanese, and reports when supplied evidence cannot support an answer.
Key takeaways
- Upstage says Solar Pro 4 is designed to complete multi-step work across documents, tools and terminal environments.
- The model supports a 512K-token context window, up to 128K output tokens, and English, Korean and Japanese input and output.
- Upstage lists standard API pricing of $0.30 per million input tokens, $0.06 per million cached input tokens and $1.20 per million output tokens.
- Solar Pro 4 is available through Upstage Console, SolarChat, OpenRouter, Hermes Agent and Upstage Studio, with dedicated and on-premises deployment also offered.
- The company says the model identifies unsupported claims and discrepancies rather than supplying unverified answers.
Upstage has launched Solar Pro 4, an agentic language model built for work that spans multiple documents, tool calls and terminal tasks. The company says the model is intended to carry assignments through to completed deliverables while identifying cases in which available evidence cannot support an answer.
Solar Pro 4 supports a 512K-token context window and up to 128K output tokens. It handles English, Korean and Japanese for both input and output. Users can also adjust reasoning effort, setting it higher for deeper analysis or lower for faster interaction.
Agent and document work
Upstage reported scores of 57.0 on Terminal-Bench v2.1, 23.0 on τ³-Banking and 71.0 on AA-LCR. The company associates those evaluations with terminal execution, multi-turn tool use and reasoning across long documents, respectively. It said those three scores came from Artificial Analysis as of August 2026, with a public listing forthcoming.
The company said Solar Pro 4 was trained using OfficeVerse, its pipeline for synthesizing office tasks from public data across 11 industry domains and 12 task types. Tasks receive a pass-or-fail grade based on the final deliverable. Upstage said its Korean office-work benchmark, Ko-GDPval, came from the same effort.
To demonstrate the model, Upstage gave it a fictional store-location assignment containing one policy document and six market-data files. According to the company, three prompts directed Solar Pro 4 to screen 10 candidate sites and produce an Excel workbook, a review report and a slide deck in sequence. Upstage said a value calculated in the workbook carried into the report unchanged.
Upstage is also releasing seven work agents through the Solar Pro 4 Agent Cookbook. The examples cover Excel workbook generation, evidence-based Word reports and PowerPoint presentations with charts and speaker notes. Each includes a system prompt, outputs and pass criteria.
Evidence handling
Upstage says Solar Pro 4 can distinguish supported answers from missing or conflicting information. In a test using a fictional service agreement and quotation, the company asked 10 questions, half of which had answers in the supplied documents. It said the model cited present clauses, marked absent material as not in the document and reported differing figures as mismatches.
The cookbook also includes a research agent that, according to Upstage, links every sentence to a source and labels material it cannot ground as unverified.
Access and pricing
Solar Pro 4 is available through the Upstage Console API under the model name solar-pro4. Upstage says the API is OpenAI-compatible. The model is also offered through SolarChat, OpenRouter, Hermes Agent and Upstage Studio. Dedicated and on-premises deployments are available by contacting the company.
Upstage lists prices per million tokens at $0.30 for input, $0.06 for cached input and $1.20 for output. The company announced a 90% discount on Upstage Console through September 10 at 23:59 UTC and also said a 90% OpenRouter promotion runs through September 10. A separate Hermes Agent offer runs through September 15.
Source: Upstage’s “Solar Pro 4: The Agentic Model That Finishes the Job” announcement, published August 11, 2026.
Frequently asked questions
- What is Solar Pro 4 designed to do?
- Upstage describes Solar Pro 4 as an agentic model for multi-step work involving tool calls, terminal tasks and reasoning across long documents.
- What context and output limits does Solar Pro 4 support?
- The company says the model supports a 512K-token context window and up to 128K output tokens.
- Which languages does Solar Pro 4 support?
- Upstage says Solar Pro 4 accepts and generates English, Korean and Japanese.
- How can customers access Solar Pro 4?
- Upstage lists access through its Console API, SolarChat, OpenRouter, Hermes Agent and Upstage Studio. It also offers dedicated and on-premises deployment.