Upstage: Solar Pro 4
Solar Pro 4 is a reasoning model from Upstage released on Aug 6, 2026. It reads text and writes text, with a 524K token context window and up to 131K tokens per reply.
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It costs $0.30 per million input tokens and $1.20 per million output tokens. Cached input bills at $0.06, 80% less than fresh input.
It supports tool calling, structured JSON output and prompt caching.
5 providers serve it, including LLMTR, NanoGPT and AI/ML API. The lowest input price is $0.03 per million tokens at LLMTR.
- Modalities
- In / out price
- $0.30 / $1.20 per 1M
- Context
- 524K
- Max output
- 131K
- Released
- Aug 6, 2026
- Knowledge cutoff
- Feb 2026
- Tool calling
- Structured output
- Reasoning
- Prompt caching
- Open weights
- Free to use
Solar Pro 4 pricing
USD, as listed on Oct 15, 2026. Most bills are input heavy, so the cached input rate matters as much as the headline price.
| Input | $0.30 / 1M tokens | |
|---|---|---|
| Output | $1.20 / 1M tokens | |
| Cached input (read) | $0.06 / 1M tokens | 80% off input |
Solar Pro 4 providers
5 providers serve it, including LLMTR, NanoGPT and AI/ML API. The lowest input price is $0.03 per million tokens at LLMTR. Each host sets its own price and limits, so the cheapest one is not always the one with the longest context.
| Provider | Input /M | Output /M | Cache read /M | Context | Max output |
|---|---|---|---|---|---|
| Upstage First party | $0.30 | $1.20 | $0.06 | 524K | 131K |
| LLMTR | $0.03 | $0.12 | – | 524K | 131K |
| NanoGPT | $0.03 | $0.12 | $0.006 | 524K | 131K |
| AI/ML API | $0.0413 | $0.165 | $0.0083 | 524K | 131K |
| Kilo Gateway | $0.30 | $1.20 | $0.06 | 524K | 131K |
What Solar Pro 4 costs per month
Pick a workload close to yours or type your own volumes.
Supported request parameters
What you can set when you call Solar Pro 4 through an OpenAI compatible API.
- Tools
tools - Structured outputs
structured_outputs - Reasoning
reasoning - Temperature
temperature
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Solar Pro 4 questions
How much does the Solar Pro 4 API cost?
$0.30 per million input tokens and $1.20 per million output tokens, with cached input at $0.06. The estimator on this page turns that into a monthly bill for your own workload.
What is the context window of Solar Pro 4?
524,288 tokens of input, and it can write up to 131,072 tokens in one reply. As a rough guide, a million tokens is around 750,000 English words.
Which providers serve Solar Pro 4?
5 providers serve it, including LLMTR, NanoGPT and AI/ML API. The lowest input price is $0.03 per million tokens at LLMTR. Prices differ by host, so the Providers table on this page lists each one with its input and output price.
Does Solar Pro 4 support tool calling?
Yes. It accepts tool definitions and can return JSON that matches a schema, which is what an agent needs to call your APIs.
Is Solar Pro 4 open source?
No. Upstage serves it through an API only, so you cannot download the weights or host it yourself.
When was Solar Pro 4 released?
Aug 6, 2026, with training data up to Feb 2026.
Catalog data from models.dev (MIT licensed), refreshed daily, last on Oct 15, 2026. The summary is written from these facts.
Building on Solar Pro 4?
I test your real tasks on it and the two closest alternatives, then ship the agent on whichever wins on cost and accuracy.
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