UltraGPT
Upstage: 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, document-intensive...
Intelligence overview
524.3K tok
Context window
131.1K tok
Max output
What Upstage: Solar Pro 4 can do.
Reasoning
Extended reasoning
Works through problems step by step before answering, trading latency for accuracy on harder tasks.
Development
Tool calling
Calls external functions mid-response, then continues reasoning from the result.
Structured output
Returns responses constrained to a JSON schema, ready to parse without cleanup.
Streaming
Streams tokens as they're generated instead of waiting on the full response.
Performance
Design Arena — ranked #32 across 7 categories
Pay for what you use.
Every model in UltraGPT runs behind one flat subscription — this is the underlying per-token cost the catalog tracks.
$0.09 / 1M tok
$0.36 / 1M tok
Built for serious work.
Build
Generate and refactor code, with the ability to run and verify tool calls and return structured, parseable output.
Think
Works through multi-step problems with extended reasoning before it answers.
Research
Holds up to 524.3K tokens of source material in context without losing the thread.
Automate
Chains tool calls across multi-step workflows, reasoning between each one.
Ask Upstage: Solar Pro 4 anything.
A preview of the real UltraGPT composer — the model you see here is the model you get.
Continues in the UltraGPT app — one login, every model.
How Upstage: Solar Pro 4 stacks up.
The closest models in the catalog by provider, capability and score — real entries, pulled from the same directory.
Technical details.
Specification
- Context window
- 524.3K tokens
- Max output
- 131.1K tokens
- Input modalities
- Text
- Output modalities
- Text
- Knowledge cutoff
- Feb 1, 2026
- Release date
- Aug 6, 2026
- Streaming
- Supported
- Tool calling
- Supported
- JSON mode
- Supported
More from Upstage, and everything else.
This model is one entry in the full UltraGPT catalog — browse the rest, compare pricing and context windows, or filter by capability.