DeepSeek V4 Pro vs GPT-5.6 Sol
Which one to choose
Pick DeepSeek V4 Pro for agentic coding, math and STEM reasoning on text-only inputs, with open weights; pick GPT-5.6 Sol for complex professional work that includes images and schema-checked JSON. Sol is the flagship of a family OpenAI now lists as legacy, so for brand-new builds also look at GPT-6. Both let you adjust how much the model thinks.
Pricing comparison
| DeepSeek V4 Pro | GPT-5.6 Sol | |
|---|---|---|
| Model maker | DeepSeek | OpenAI |
| Delivery availability | Available | Available |
| Context window | 1M | 1.05M |
| Max output | 384K | 128K |
| Official price | Input$0.66per 1M tokensOutput$1.98per 1M tokens | Input$4.00per 1M tokensOutput$20.00per 1M tokens |
| TokenLab price | — | Input$1.20per 1M tokensOutput$6.00per 1M tokens |
| Model performance |
|
|
| Capabilities | JSON modePrompt CacheTool use | CodeJSON modePrompt CacheReasoningTool useVision |
Choose DeepSeek V4 Pro when
- Your tasks are agentic coding, hard math or STEM problems with text-only input.
- You run coding agents and want to set thinking effort from low to max.
- You want open weights, so a team can test the same family locally.
Choose GPT-5.6 Sol when
- A request must read a diagram or screenshot and return JSON that matches a schema.
- The work is complex professional analysis, scientific work or long multi-step agent runs.
- You want to spend thinking time only on the turns that need it, through reasoning effort.
How they differ
| Aspect | DeepSeek V4 Pro | GPT-5.6 Sol |
|---|---|---|
| Openness | Open-weight mixture-of-experts model. | Closed model from OpenAI. |
| Input types | Text only; image inputs need deepseek-v4.1-flash. | Text and image input. |
| Reasoning control | Thinking and non-thinking modes with low, high and max effort; max produces long reasoning. | Adjustable reasoning effort for each request. |
| Structured output | JSON output on request. | Schema-checked JSON output. |
| Lifecycle | The heavier V4 model; V4 Flash answers faster when depth is not needed. | Flagship of GPT-5.6, which OpenAI lists as legacy in favor of GPT-6. |
Summary
- DeepSeek V4 Pro: Input $0.66 / Output $1.98 per 1M tokens; GPT-5.6 Sol: Input $1.20 / 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.
- DeepSeek V4 Pro supports 3.0x more output tokens
FAQ
Is DeepSeek V4 Pro better than GPT-5.6 Sol?
It depends on the job. DeepSeek calls V4 Pro the open-source leader on agentic coding benchmarks, and OpenAI reports Sol ahead of Claude Fable 5 on its Agents' Last Exam. For image input, only Sol applies. Test both on your own tasks.
Which should I choose for a coding agent?
V4 Pro is built for agentic coding and lets you raise thinking effort to max on hard steps. Sol handles complex coding and long agent runs and also reads screenshots. Pick by whether your agent needs images.
Do I need to change my prompts to switch?
Plain prompts transfer, but agent code needs a check. V4 Pro returns reasoning text separately and expects it back on every tool turn. Sol is steered through reasoning effort instead. Re-run your evaluation set.
Should a new project use GPT-5.6 Sol?
OpenAI's guidance lists the GPT-5.6 family as legacy and recommends GPT-6 models for new builds. Sol is still reasonable for existing workloads; for a new build compare it with DeepSeek V4 Pro and GPT-6.
Which is cheaper, DeepSeek V4 Pro or GPT-5.6 Sol?
DeepSeek V4 Pro: Input $0.66 / Output $1.98 per 1M tokens; GPT-5.6 Sol: Input $1.20 / 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 DeepSeek V4 Pro and GPT-5.6 Sol?
GPT-5.6 Sol: Code, Reasoning, Vision
Sources
- DeepSeek V4 release
- DeepSeek updates
- DeepSeek thinking mode
- Introducing GPT-5.6
- OpenAI latest model guide
Reviewed Oct 2, 2026