solar-mini4
Solar Mini 4 is Upstage’s compact, cost-efficient language model: a 35B-parameter Mixture-of-Experts with 3B active parameters and a 524K-token context window, built for agentic use cases.
Pricing: Input 10 credits / 1M tokens (≈ $0.05), Output 40 credits / 1M tokens (≈ $0.20).
Prices updated
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Solar Mini 4 API on ModelFold
Solar Mini 4 is Upstage’s compact, cost-efficient language model: a 35B-parameter Mixture-of-Experts with 3B active parameters and a 524K-token context window, built for agentic use cases. Try Solar Mini 4 in the ModelFold Playground, then call it from your own code through an OpenAI-compatible chat completions API.
What Is the Solar Mini 4 API
Solar Mini 4 at a glance
Solar Mini 4 is a chat model from Upstage. It accepts text as input and returns text, with a context window of up to 524K tokens.
Use it without hosting anything
On ModelFold you call Solar Mini 4 with a single API key — no model weights to download and no inference servers to run. The same key also works for the other chat, image, video and audio models on ModelFold.
Core Capabilities of Solar Mini 4
Up to 524K tokens of context
Keep long conversations, large documents and sizeable code in a single request, so the model can reason over the full material instead of fragments.
Function calling
Solar Mini 4 supports tool (function) calling: describe your functions in the request and the model returns structured calls your code can run — the basis for agents and integrations.
Adjustable reasoning effort
Choose a reasoning effort level (low, medium or high) per request to balance depth of thinking against speed and token usage.
Structured outputs
Ask for JSON that follows a schema (response_format), which makes extraction, classification and system integrations more reliable.
How to Use Solar Mini 4 on ModelFold
- 1
Step 1: Try it in the Playground
Open the Playground at the top of this page, type a prompt and see how Solar Mini 4 responds before writing any code.
- 2
Step 2: Create an API key
Sign in to ModelFold and create an API key in the console. Keep it secret and send it as a Bearer token.
- 3
Step 3: Send a request
Call POST https://modelfold.ai/v1/chat/completions with "model": "solar-mini4" and your messages. Existing OpenAI-compatible SDKs work by changing the base URL and key.
- ✓
Step 4: Ship and monitor
Integrate the response into your product and check token usage and spend for every call in the console logs.
What You Can Build with Solar Mini 4
High-volume pipelines
Run classification, extraction, rewriting and batch jobs at scale where cost per request matters.
Autonomous agents
Build agents that plan multi-step tasks, call your tools and APIs, and keep working toward a goal across long sessions.
Long-document workflows
Feed in long reports, contracts, manuals or codebases and ask for summaries, comparisons and answers grounded in the material.
Low-latency experiences
Power chat interfaces, autocomplete and interactive tools where users expect fast responses.
Frequently Asked Questions
What is Solar Mini 4?⌄
Solar Mini 4 is Upstage’s compact, cost-efficient language model: a 35B-parameter Mixture-of-Experts with 3B active parameters and a 524K-token context window, built for agentic use cases.
Which inputs does Solar Mini 4 support?⌄
Solar Mini 4 accepts text and returns text. Through ModelFold you send text messages; documents attached in the Playground are converted to text.
How long is the context window of Solar Mini 4?⌄
Up to 524K tokens, shared between your input and the model’s output.
Does Solar Mini 4 support function calling?⌄
Yes. Solar Mini 4 supports tools / function calling through the standard tools parameter of the chat completions API.
How is Solar Mini 4 billed on ModelFold?⌄
Pay as you go by tokens: input and output tokens are charged at the per-million-token prices shown on this page. There is no monthly fee, and failed requests are not charged.
How do I call Solar Mini 4 through the API?⌄
Send a POST request to https://modelfold.ai/v1/chat/completions with "model": "solar-mini4", using your ModelFold API key as the Bearer token.
| Input | 10 credits 1M tokens≈ $0.05 |
| Output | 40 credits 1M tokens≈ $0.20 |
Billed per token: input and output are priced separately, and thinking tokens count as output. The Playground charges exactly the same way.
Read API docs →AI Agents · Claude Code / Cursor / Trae →curl https://modelfold.ai/v1/chat/completions \
-H "Authorization: Bearer $MODELFOLD_API_KEY" \
-H "Content-Type: application/json" \
-d '{"model":"solar-mini4","messages":[{"role":"user","content":"Hello"}]}'