# Solar Pro 4

Canonical: https://freepi.ai/models/solar-pro-4

Use Solar Pro 4 free in free-pi: run `npx free-pi-cli`, then `/model solar-pro-4`.

Usage in free-pi: \~1.6x usage

## About 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](https://freepi.ai/models/deepseek-v4-flash) or [GLM-5.3 Flash](https://freepi.ai/models/glm-5.3-flash). To show the model images, pick a multimodal model such as [Claude Haiku 5.5](https://freepi.ai/models/claude-haiku-5.5).