Overview
GPT-5.6 Sol Pro is the same underlying model as [GPT-5.6 Sol](https://openrouter.ai/openai/gpt-5.6-sol), served with `reasoning.mode` set to `pro` for higher-quality responses on complex tasks. **Cost note:** pro mode spends far more...
Our take
In a category where most models now advertise reasoning and long context, this sits at the top of OpenAI's GPT-5.6 line: the flagship Sol tier, served with reasoning set to 'pro' for maximum deliberation on the hardest problems. Where the Luna and Terra tiers optimise for cost and balance, this one is aimed at work that justifies the highest effort — intricate multi-step coding, deep research, and agent runs where a wrong intermediate step is expensive. Its 1,050,000-token context window is larger than most models listed here, and it pairs that with chain-of-thought reasoning, vision input, tool and function calling, and structured JSON output, so it can read a large codebase or research corpus and return machine-readable conclusions. Compared with the general assistants it is grouped with — Claude, ChatGPT, Gemini, Kimi K3 — this is the deliberate, top-tier API option rather than a consumer chat interface. That standing comes at a price: $5.00 per 1M input tokens, above average for the category, with no free tier. Ideal for teams tackling genuinely hard reasoning and coding problems who can justify premium rates. For routine or high-volume calls, the cheaper Terra or Luna tiers do the same job for far less.
How OpenAI: GPT-5.6 Sol Pro stacks up
Among the 372 chatbots & llms tools in our directory, it ranks #3 of 367 on quality (9.2/10), 14% above the 367-tool average of 8.0, and its $2/1M input-token rate is in the premium end — 3% pricier than the 355-model average of $1.95/1M.
Weighing quality against cost, OpenAI: GPT-5.6 Sol Pro's cost-per-quality-point of $0.22 places it at #266 of 346 for value among chatbots & llms tools.
OpenAI: GPT-5.6 Sol Pro in depth
OpenAI: GPT-5.6 Sol Pro, built by OpenAI, sits in the chatbots & llms space and is a paid tool starting at $2.00/1M tokens. Our editors rate it 9.2 out of 10 based on capability, ecosystem and value. It handles a context window of 1,050,000 tokens.
On the feature side, OpenAI: GPT-5.6 Sol Pro brings 1,050,000-token context window, vision (image input), reasoning / chain-of-thought and tool / function calling. These are the capabilities that most shape day-to-day use and separate it from thinner alternatives.
Its biggest strength is large 1,050,000-token context window, bigger than most models listed here, while the main trade-off to weigh is that above-average api pricing ($2 per 1m input tokens). Keep both in mind when deciding whether it fits your workflow.
OpenAI: GPT-5.6 Sol Pro is most often chosen for research and writing. If that matches your goals, it's a strong candidate to shortlist.
Key features
- ✓1,050,000-token context window
- ✓Vision (image input)
- ✓Reasoning / chain-of-thought
- ✓Tool / function calling
- ✓Structured (JSON) outputs
- ✓Knowledge cutoff 2026-02-16
Pricing
Pros
- +Large 1,050,000-token context window, bigger than most models listed here
- +Built-in reasoning (chain-of-thought) mode for harder problems
- +Accepts images as input (vision-capable)
- +Supports tool / function calling for agent-style workflows
Cons
- −Above-average API pricing ($2 per 1M input tokens)
Who should use OpenAI: GPT-5.6 Sol Pro
- →Anyone looking for a chatbots & llms tool from OpenAI.
- →Teams and individuals focused on research and writing.
- →People who value large 1,050,000-token context window, bigger than most models listed here.
- →Workflows that need a 1,050,000 tokens context window.
Who should look elsewhere
- →Anyone who needs a free tier — this tool is paid only.
- →Those for whom above-average api pricing ($2 per 1m input tokens) is a dealbreaker.
Best for
10 Best OpenAI: GPT-5.6 Sol Pro Alternatives in 2026
OpenAI: GPT-5.6 Sol Pro 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 OpenAI: GPT-5.6 Sol Pro, ranked and compared.
Anthropic
Claude is Anthropic's family of AI assistants, known for long-context reasoning, careful writing and strong coding…
OpenAI
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Google DeepMind
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Stepfun
Step 5 Preview is StepFun's flagship model for agentic work, built on a sparse Mixture-of-Experts architecture (27B…
Anthropic
Claude Haiku 5.5 is Anthropic's small, fast model for high-volume, cost-sensitive work such as summarization…
Mistral AI
Mistral Large 4 is a frontier multimodal (text and image input) model from Mistral AI built for reasoning, coding, and…
OpenAI
GPT-6.1 Sol Pro is the same underlying model as [GPT-6.1 Sol](https://openrouter.ai/openai/gpt-6.1-sol), served with…
OpenAI
GPT-6.1 Sol is an upgrade to GPT-6 Sol from OpenAI, positioned below the flagship GPT-6 Astra in the GPT-6 series.
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…
OpenAI: GPT-5.6 Sol Pro vs top alternatives
A side-by-side look at how OpenAI: GPT-5.6 Sol Pro stacks up against its closest rivals.
| Feature | OpenAI: GPT-5.6 Sol ProOpenAI | ClaudeAnthropic | ChatGPTOpenAI | GeminiGoogle DeepMind |
|---|---|---|---|---|
| Quality score | 9.2 / 10 | 9.6 / 10 | 9.5 / 10 | 9.2 / 10 |
| Starting price | $2.00/1M 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 | $2 / 1M tokens | $0.1 / 1M tokens | $2 / 1M tokens | $0.75 / 1M tokens |
| API output price | $10 / 1M tokens | $0.5 / 1M tokens | $10 / 1M tokens | $3.75 / 1M tokens |
| Speed | — | Fast | Fast | Fast |
| Context window | 1,050,000 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 OpenAI: GPT-5.6 Sol Pro free?
No — OpenAI: GPT-5.6 Sol Pro is a paid tool, starting at $2.00/1M tokens.
Q. How much does OpenAI: GPT-5.6 Sol Pro cost?
OpenAI: GPT-5.6 Sol Pro starts at $2.00/1M tokens. API usage is around $2 per 1M input tokens and $10 per 1M output tokens.
Q. What is OpenAI: GPT-5.6 Sol Pro best for?
OpenAI: GPT-5.6 Sol Pro is best suited to research and writing, within the chatbots & llms category.
Q. What are the best OpenAI: GPT-5.6 Sol Pro alternatives?
Popular alternatives to OpenAI: GPT-5.6 Sol Pro include Claude, ChatGPT, Gemini and StepFun: Step 5 Preview. Each trades off price, quality and ecosystem differently.
Q. Is there a free alternative to OpenAI: GPT-5.6 Sol Pro?
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 OpenAI: GPT-5.6 Sol Pro?
Common reasons include pricing, specific feature gaps (Above-average API pricing ($2 per 1M input tokens)), 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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