Solar Pro 4
Use it free in free-pi
~1.6x usage
npx free-pi-cli
/model solar-pro-4About Solar Pro 4
Solar Pro 4 is Upstage's cost-efficient large language model, featuring a 524K context window. It is built for long-horizon tasks and agentic workflows, with strong capabilities in office productivity and document-intensive work. It became available in August 2026.
The model takes text in and produces text. Its context window is 524,288 tokens and a response can be up to about 131,000 tokens. It supports reasoning with an effort setting, tool calling, and structured outputs. With tool calling, the free-pi agent can read and edit files, run commands, and use free-pi's built-in web search and documentation lookup tools.
It scores 52.7 on the Artificial Analysis Coding Index and 28.2 on the Intelligence Index.
In free-pi it is free to use with no API key and no card. It counts as about 1.6x usage, so it stretches your daily allowance further than the default.
When to pick it
For long sessions where you want your allowance to last, and for document-heavy or text-oriented work with large files, pick Solar Pro 4. Its context window of about half a million tokens is enough for big inputs.
For coding that needs stronger results, pick DeepSeek V4 Flash or GLM-5.3 Flash. To show the model images, pick a multimodal model such as Claude Haiku 5.5.