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GPT-5.6 Sol vs Gemini 3.1 Pro Preview

GPT-5.6 Sol and Gemini 3.1 Pro Preview: current price, context, max output, and supported operations.

Which one to choose

Pick GPT-5.6 Sol for the heaviest coding and scientific work and for long multi-step agent runs with adjustable reasoning effort. Pick Gemini 3.1 Pro when you want a reasoning-first model for debugging, research synthesis and visual analysis, and accept that it is a preview. The deciding factor is stability and maturity: Sol is a released flagship that OpenAI now lists as legacy, while Gemini 3.1 Pro may change or be replaced by a stable Pro release.

Pricing comparison

GPT-5.6 SolGemini 3.1 Pro Preview
Model makerOpenAIGoogle
Delivery availabilityAvailableAvailable
Context window1.05M1M
Max output128K64K
Official price
Input$4.00per 1M tokensOutput$20.00per 1M tokens
Input$2.00per 1M tokensOutput$12.00per 1M tokens
TokenLab price
Input$1.20per 1M tokensOutput$6.00per 1M tokens
Input$1.00per 1M tokensOutput$6.00per 1M tokens
Model performance
30-day success rate
86.6%
7-day median latency
18 sn=2,418
30-day success rate
80.8%
7-day median latency
15 sn=166
Capabilities
CodeJSON modePrompt CacheReasoningTool useVision
JSON modePrompt CacheTool useVision

Choose GPT-5.6 Sol when

  • You need a flagship for scientific analysis and security review.
  • You want to control reasoning effort per turn.
  • You want a released model rather than a preview whose behaviour Google may change.

Choose Gemini 3.1 Pro Preview when

  • You use a strong planner that splits a task and hands steps to cheaper models.
  • You analyse dashboards, charts or architecture diagrams next to text.
  • You combine several long documents into a reasoned comparison.

How they differ

AspectGPT-5.6 SolGemini 3.1 Pro Preview
Release statusA released model, but OpenAI's guidance now lists the GPT-5.6 family as legacy.A preview that Google may change or retire in favour of a stable Pro release.
Reasoning controlAdjustable effort so thinking is spent where needed.Thinks before answering, aimed at multi-step problems where a wrong first answer is costly.
Agent roleDrives long autonomous coding and workflow runs.Works well as a planner for edit-and-test loops and for delegating to smaller models.
Visual workReads a diagram and emits structured output in one request.Text and images in one prompt for diagram, chart and UI analysis.
Request formatsChat Completions and Responses style requests.Gemini native and Chat Completions style requests.

Summary

  • GPT-5.6 Sol: Input $1.20 / Output $6.00 per 1M tokens; Gemini 3.1 Pro Preview: Input $1.00 / Output $6.00 per 1M tokens. Rates depend on the billing unit, specification, and usage. Compare matching conditions in the model's detailed pricing; a single rate does not determine the total cost.
  • GPT-5.6 Sol supports 2.0x more output tokens
GPT-5.6 Sol
GPT 5.6
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Gemini 3.1 Pro Preview
Gemini 3
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FAQ

Is Gemini 3.1 Pro better than GPT-5.6 Sol?

Neither is better in general. GPT-5.6 Sol is OpenAI's flagship for the hardest professional work; Gemini 3.1 Pro is Google's reasoning-first Pro preview. Compare them on your hardest prompts.

Is Gemini 3.1 Pro stable enough for production?

It is a preview, so Google may change its behaviour or retire it. If you need stable behaviour, plan a regression test for each change or choose a released model.

Can I switch between them without prompt changes?

Both accept Chat Completions requests, so the basic call shape carries over. Reasoning controls, tool schemas and output style differ between the makers, so re-run your own evaluation set before switching.

Is GPT-5.6 Sol still recommended by OpenAI?

OpenAI now points new projects to GPT-6 models and lists the GPT-5.6 family as legacy. Sol remains fine for existing integrations that you have already tested.

Which is cheaper, GPT-5.6 Sol or Gemini 3.1 Pro Preview?

GPT-5.6 Sol: Input $1.20 / Output $6.00 per 1M tokens; Gemini 3.1 Pro Preview: Input $1.00 / Output $6.00 per 1M tokens. Rates depend on the billing unit, specification, and usage. Compare matching conditions in the model's detailed pricing; a single rate does not determine the total cost.

What are the key differences between GPT-5.6 Sol and Gemini 3.1 Pro Preview?

GPT-5.6 Sol: Code, Reasoning

Sources

Reviewed Oct 2, 2026