Everything about Solar Mini 4

Overview

Solar Mini 4 is a language model from Upstage, released on September 22, 2026. It is a very recent release. It is a closed model: you access it through an API, from Upstage or one of the 4 providers listed on models.dev. It has a reasoning mode: it can "think" before answering, which helps with multi-step problems but uses more tokens, and therefore more money.

We file it under budget models (24 models in this category on the site).

What do independent benchmarks say?

As of October 22, 2026, Epoch AI publishes no score for Solar Mini 4 on our basket's benchmarks. To place it, rely on its specifications and price, then test it on your own cases.

How much does Solar Mini 4 cost?

Solar Mini 4 costs $0.10 per million input tokens and $0.40 per million output tokens (developer's price, checked on October 22, 2026).

To put it in perspective: reading 20,000 tokens (about thirty pages) and writing 2,000 costs roughly $0.003; a thousand of those tasks, $2.8.

That is 2.8 times cheaper than the median output price of budget models ($1.13).

Tokens read back from cache cost $0.01 per million, which helps an agent that keeps resending the same context.

To estimate your own budget, use the agent cost calculator.

Technical specifications

Its context window reaches 524,288 tokens, roughly 786 pages of text at 500 words per page: enough for a long report or several contracts at once. A single answer can run to 131,072 tokens.

It accepts as input: text. Its knowledge stops at February 2026: beyond that, it needs web search or your documents.

It can call tools (functions, APIs) and return structured JSON output, which makes it a possible foundation for an AI agent.

When to choose it

Given its category, Solar Mini 4 is mainly aimed at high volumes where every cent counts: sorting, information extraction, summaries, simple assistants.

Its very low cost (under half a cent for our sample task) means it can be called thousands of times a day.

Before adopting it, test it on your own examples: benchmarks measure standard tasks, not your job.

Comparable models

In the same category, the models closest to Solar Mini 4 are:

• Qwen3.5 Flash (Alibaba Cloud (Qwen), index 62.6)
• Seed 2.0 Mini (ByteDance Seed, $0.40 per million output tokens)
• Mercury 3 (Inception, $0.35 per million output tokens)
• GPT-6 Luna (OpenAI, index 80.3)