GPT-5.6 Sol vs GPT-5.5
Which one to choose
Pick GPT-5.6 Sol for long agentic runs, complex coding and scientific analysis where you want the flagship of the newer GPT-5.6 family and its Sol, Terra and Luna tiers to choose from. Pick GPT-5.5 when you want the established GPT-5 flagship with a documented tool list covering computer use, hosted shell, patch application and MCP, and you have prompts tuned for it. Both take text and images and offer adjustable reasoning effort.
Pricing comparison
| GPT-5.6 Sol | GPT-5.5 | |
|---|---|---|
| Model maker | OpenAI | OpenAI |
| Delivery availability | Available | Available |
| Context window | 1.05M | 1M |
| Max output | 128K | 128K |
| Official price | Input$4.00per 1M tokensOutput$20.00per 1M tokens | Input$5.00per 1M tokensOutput$30.00per 1M tokens |
| TokenLab price | Input$1.20per 1M tokensOutput$6.00per 1M tokens | Input$1.50per 1M tokensOutput$9.00per 1M tokens |
| Model performance |
|
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| Capabilities | CodeJSON modePrompt CacheReasoningTool useVision | CodeJSON modePrompt CacheReasoningTool useVision |
Choose GPT-5.6 Sol when
- You run multi-step agents on hard coding or scientific problems
- You want to pair Sol with cheaper Terra or Luna in the same family
- You build on the newer GPT-5.6 generation
Choose GPT-5.5 when
- You have prompts and evaluations tuned to GPT-5.5
- You use its documented tools: computer use, hosted shell, patch application, MCP, web search, file search
- You want the default medium reasoning effort with levels from none to xhigh
How they differ
| Aspect | GPT-5.6 Sol | GPT-5.5 |
|---|---|---|
| Generation | Flagship of the GPT-5.6 family, released after GPT-5.5. | GPT-5 flagship for complex professional work and coding. |
| Family structure | Sits above Terra and Luna, so cheaper siblings with the same interface exist. | Offered as a single flagship, with a Pro tier for the hardest questions. |
| Agent focus | OpenAI describes it for long multi-step agent workflows and reports it ahead of Claude Fable 5 on its Agents' Last Exam benchmark. | Documented with computer use, hosted shell, patch application and MCP as tools. |
| Reasoning control | Adjustable effort so thinking time goes to turns that need it. | Five effort levels, none through xhigh, with medium as default. |
| Guidance status | OpenAI lists the GPT-5.6 family as legacy and points new work to GPT-6. | The earlier flagship; its page does not recommend it over later models. |
Summary
- GPT-5.6 Sol: Input $1.20 / Output $6.00 per 1M tokens; GPT-5.5: Input $1.50 / Output $9.00 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.
FAQ
Is GPT-5.6 Sol better than GPT-5.5?
It is the newer flagship and targets the same hard coding and agent work, so it is the natural step up. If your GPT-5.5 prompts are tuned and working, move after testing your own cases.
Can I swap GPT-5.5 for GPT-5.6 Sol without prompt changes?
Usually, since both use the same chat interface, take text and images, and call tools. Check reasoning effort settings and compare outputs on your evaluation set before switching.
Which is better for coding?
GPT-5.6 Sol, which OpenAI aims at complex coding and long agent runs. GPT-5.5 also handles coding and offers patch application and hosted shell as documented tools.
Should new projects use either?
OpenAI's guidance now points new projects to GPT-6 models rather than either of these. Between the two, GPT-5.6 Sol is the more recent flagship and the likelier choice for new work.
Which is cheaper, GPT-5.6 Sol or GPT-5.5?
GPT-5.6 Sol: Input $1.20 / Output $6.00 per 1M tokens; GPT-5.5: Input $1.50 / Output $9.00 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 GPT-5.5?
Both models share similar capabilities.
Sources
Reviewed Oct 2, 2026