Overview
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...
Our take
For organisations needing to automate document-intensive workflows, Solar Pro 4 offers a substantial 524,288-token context window, allowing for extensive data processing. Unlike competitors such as Claude or ChatGPT which may be used more broadly, this model's focus on agentic workflows, coupled with its support for tool/function calling and structured JSON outputs, positions it for integration into automated systems. Its built-in reasoning mode further supports tackling complex problems. With an API price of $0.03 per 1M input tokens, it is positioned as a more cost-effective option than roughly 75% of comparable models, though the absence of a free tier means all usage incurs a charge. Ideal for developers or businesses aiming to build AI agents for office productivity or coding tasks, particularly those requiring reliable, structured outputs from text-based inputs. Those needing multimodal capabilities, however, will need to look elsewhere.
How Upstage: Solar Pro 4 stacks up
Among the 376 chatbots & llms tools in our directory, it ranks #138 of 371 on quality (8.2/10), 2% above the 371-tool average of 8.0, and its $0.09/1M input-token rate is in the budget end — 95% cheaper than the 360-model average of $1.93/1M.
Weighing quality against cost, Upstage: Solar Pro 4's cost-per-quality-point of $0.01 places it in the top 14% for value among chatbots & llms tools.
Upstage: Solar Pro 4 in depth
Upstage: Solar Pro 4, built by Upstage, sits in the chatbots & llms space and is a paid tool starting at $0.09/1M tokens. Our editors rate it 8.2 out of 10 based on capability, ecosystem and value. It handles a context window of 524,288 tokens.
On the feature side, Upstage: Solar Pro 4 brings 524,288-token context window, reasoning / chain-of-thought, tool / function calling and structured (json) outputs. These are the capabilities that most shape day-to-day use and separate it from thinner alternatives.
Its biggest strength is low api price — $0.09 per 1m input tokens, cheaper than roughly 75% of comparable models, while the main trade-off to weigh is that no free tier — usage is billed per token. Keep both in mind when deciding whether it fits your workflow.
Upstage: Solar Pro 4 is most often chosen for research and writing. If that matches your goals, it's a strong candidate to shortlist.
Key features
- ✓524,288-token context window
- ✓Reasoning / chain-of-thought
- ✓Tool / function calling
- ✓Structured (JSON) outputs
Pricing
Pros
- +Low API price — $0.09 per 1M input tokens, cheaper than roughly 75% of comparable models
- +Built-in reasoning (chain-of-thought) mode for harder problems
- +Supports tool / function calling for agent-style workflows
- +Can return structured JSON output for reliable parsing
Cons
- −No free tier — usage is billed per token
- −Text-only: does not accept image input
Who should use Upstage: Solar Pro 4
- →Anyone looking for a chatbots & llms tool from Upstage.
- →Teams and individuals focused on research and writing.
- →People who value low api price — $0.09 per 1m input tokens, cheaper than roughly 75% of comparable models.
- →Workflows that need a 524,288 tokens context window.
Who should look elsewhere
- →Anyone who needs a free tier — this tool is paid only.
- →Those for whom no free tier — usage is billed per token is a dealbreaker.
- →Users who can't accept that text-only: does not accept image input.
Best for
10 Best Upstage: Solar Pro 4 Alternatives in 2026
Upstage: Solar Pro 4 is a strong chatbots & llms tool, but it is not the only option. Whether you are after a lower price, different features or a better fit for your workflow, here are the 10 best alternatives to Upstage: Solar Pro 4, ranked and compared.
Anthropic
Claude is Anthropic's family of AI assistants, known for long-context reasoning, careful writing and strong coding…
OpenAI
ChatGPT is OpenAI's flagship conversational AI, powering hundreds of millions of weekly users across web, mobile and…
Google DeepMind
Gemini is Google's natively multimodal model family, deeply integrated across Search, Workspace, Android and the Pixel…
Anthropic
Claude Sonnet 5.5 is Anthropic's Sonnet-class model for well-scoped everyday work, succeeding Claude Sonnet 5 as a…
Fireworks
Ember-1 is a specialized reasoning model from Fireworks Research, built on [Kimi…
Qwen
Qwen3.8 Max Prime is a higher-throughput variant of Qwen3.8 Max from Alibaba's Qwen team, served as a separate SKU at a…
Stealth
Space Bunny Alpha is an anonymous large model with blazing-fast inference, strong coding capabilities and native…
OpenAI
GPT-6 Luna Pro is the same underlying model as [GPT-6 Luna](https://openrouter.ai/openai/gpt-6-luna), served with…
OpenAI
GPT-6 Luna is the fast, cost-efficient model in OpenAI's GPT-6 series, positioned below GPT-6 Sol.
OpenAI
GPT-6 Sol Pro is the same underlying model as [GPT-6 Sol](https://openrouter.ai/openai/gpt-6-sol), served with…
Upstage: Solar Pro 4 vs top alternatives
A side-by-side look at how Upstage: Solar Pro 4 stacks up against its closest rivals.
| Feature | Upstage: Solar Pro 4Upstage | ClaudeAnthropic | ChatGPTOpenAI | GeminiGoogle DeepMind |
|---|---|---|---|---|
| Quality score | 8.2 / 10 | 9.6 / 10 | 9.5 / 10 | 9.2 / 10 |
| Starting price | $0.09/1M tokens | $20/mo | $20/mo | $20/mo |
| Free tier | No | Yes — Free tier available | Yes — Free tier available | Yes — Free tier available |
| API input price | $0.09 / 1M tokens | $2 / 1M tokens | $0.1 / 1M tokens | $0.75 / 1M tokens |
| API output price | $0.36 / 1M tokens | $10 / 1M tokens | $0.5 / 1M tokens | $3.75 / 1M tokens |
| Speed | — | Fast | Fast | Fast |
| Context window | 524,288 tokens | 200K tokens | 128K tokens | 1M-2M tokens |
| Categories | Chatbots & LLMs | Chatbots & LLMs, Coding, Writing | Chatbots & LLMs, Coding, Writing | Chatbots & LLMs, Coding, Writing |
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Frequently asked questions
Q. Is Upstage: Solar Pro 4 free?
No — Upstage: Solar Pro 4 is a paid tool, starting at $0.09/1M tokens.
Q. How much does Upstage: Solar Pro 4 cost?
Upstage: Solar Pro 4 starts at $0.09/1M tokens. API usage is around $0.09 per 1M input tokens and $0.36 per 1M output tokens.
Q. What is Upstage: Solar Pro 4 best for?
Upstage: Solar Pro 4 is best suited to research and writing, within the chatbots & llms category.
Q. What are the best Upstage: Solar Pro 4 alternatives?
Popular alternatives to Upstage: Solar Pro 4 include Claude, ChatGPT, Gemini and Anthropic: Claude Sonnet 5.5. Each trades off price, quality and ecosystem differently.
Q. Is there a free alternative to Upstage: Solar Pro 4?
Yes. Claude, ChatGPT, Gemini offer a free tier, making them good starting points if you want to avoid an upfront subscription.
Q. Why switch from Upstage: Solar Pro 4?
Common reasons include pricing, specific feature gaps (No free tier — usage is billed per token; Text-only: does not accept image input), data-privacy requirements, or simply wanting a tool that fits your stack better.
How we rate AI tools
Our quality score weighs capability on real tasks, breadth of features and integrations, pricing and value, and how actively the tool is maintained. Scores are editorial guidance, not benchmarks — always trial a tool on your own workflow before committing. Pricing and features change frequently, so verify current details on the official site.
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