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What is GPT-5.6 Sol?
GPT-5.6 Sol is OpenAI's frontier model in the GPT-5.6 family. OpenAI positions it as the flagship GPT-5.6 tier for complex professional work, and the gpt-5.6 alias routes API requests to GPT-5.6 Sol.
Released for general availability on July 9, 2026, GPT-5.6 Sol is designed for demanding work across coding, knowledge work, research, cybersecurity, science, computer use, and design. It supports text and image input, text output, long context, reasoning tokens, structured outputs, function calling, streaming, and Responses API tool workflows.
GPT-5.6 Sol: Key Specs
Below are GPT-5.6 Sol's main specs and how they translate into real-world behavior.
- 1,050,000-token context window: GPT-5.6 Sol can process very large prompts, long documents, codebases, research corpora, or retrieval bundles, which helps reduce chunking in complex workflows.
- 128,000 maximum output tokens: the model can generate long structured answers, reports, code plans, reviews, and multi-section outputs when tasks require extended responses.
- Text and image input with text output: GPT-5.6 Sol can interpret written and visual context while returning text, supporting document review, screenshot analysis, computer-use tasks, and multimodal reasoning.
- Highest reasoning with reasoning token support: GPT-5.6 Sol supports deeper reasoning for difficult coding, analysis, research, scientific, cybersecurity, and agentic tasks.
- $5.00 per 1M input tokens, $0.50 per 1M cached input tokens, and $30.00 per 1M output tokens: this pricing places Sol above Terra and Luna as the flagship GPT-5.6 API model.
- Streaming, function calling, structured outputs, and Responses API tools: GPT-5.6 Sol supports workflows using web search, file search, image generation, code interpreter, hosted shell, apply patch, skills, computer use, MCP, and tool search.
Compare GPT-5.6 Sol, GPT-5.6 Terra & GPT-5.6 Luna
A brief overview of how each model differs in power, speed, and use cases.
| Feature | GPT-5.6 Sol | GPT-5.6 Terra | GPT-5.6 Luna |
|---|---|---|---|
| Knowledge Cutoff | February 16, 2026 | February 16, 2026 | February 16, 2026 |
| Context Window (Tokens) | 1,050,000 tokens | 1,050,000 tokens | 1,050,000 tokens |
| Max Output Tokens | 128,000 tokens | 128,000 tokens | 128,000 tokens |
| Input Modalities | Text, image | Text, image | Text, image |
| Output Modalities | Text | Text | Text |
| Latency (OpenRouter Data) | Fast; real-world latency varies by prompt length, output length, tool use, reasoning effort, and deployment conditions. | Fast; real-world latency varies by prompt length, output length, tool use, reasoning effort, and deployment conditions. | Fast; real-world latency varies by prompt length, output length, tool use, reasoning effort, and deployment conditions. |
| Speed | Fast | Fast | Fast |
| Input / Output Cost per 1M Tokens | $5.00 input, $0.50 cached input, $30.00 output | $2.50 input, $0.25 cached input, $15.00 output | $1.00 input, $0.10 cached input, $6.00 output |
| Reasoning Performance | Highest. Official GPT-5.6 evaluations list Sol at 52.7% on Agents' Last Exam, 1,747.8 Elo on GDPval-AA v2, 58.9 on Artificial Analysis Intelligence Index v4.1, 90.4% on BrowseComp, and 62.6% on OSWorld 2.0. | High. Official GPT-5.6 evaluations list Terra at 50.4% on Agents' Last Exam, 55 on Artificial Analysis Intelligence Index v4.1, 57.7% on HealthBench Professional, and 87.5% on BrowseComp. | High. Official GPT-5.6 Luna evaluations include GPQA Diamond 92.3%, FrontierMath Tier 1-3 v2 78.6%, FrontierMath Tier 4 v2 58.5%, and Artificial Analysis Intelligence Index v4.1 score 51.2. |
| Coding Performance (on SWE-bench Verified) | Very strong. Official GPT-5.6 evaluations list Sol at 80 on Artificial Analysis Coding Agent Index v1.1, 64.6% on SWE-Bench Pro, 72.7% on DeepSWE v1.1, and 88.8% on Terminal-Bench 2.1. | Strong. Official GPT-5.6 evaluations list Terra at 77.4 on Artificial Analysis Coding Agent Index v1.1, 63.4% on SWE-Bench Pro, 69.6% on DeepSWE v1.1, and 87.4% on Terminal-Bench 2.1. | Strong for a lower-cost model. Official evaluations include Artificial Analysis Coding Agent Index v1.1 score 74.6, SWE-Bench Pro 62.7%, DeepSWE v1.1 67.2%, and Terminal-Bench 2.1 84.7%. |
| Best For | Complex reasoning, professional coding, long-context research, knowledge work, cybersecurity, science, computer use, design, and advanced agent workflows | Production coding, structured data extraction, content workflows, general-purpose agents, long-context analysis, and cost-aware knowledge work | High-volume classification, summarization, routing, structured extraction, real-time applications, coding support, and cost-sensitive agent workflows |
Source: OpenAI GPT-5.6 Sol Documentation
Best Cases to Use GPT-5.6 Sol
Best GPT-5.6 Sol use cases
- complex coding and software engineering workflows that require planning, implementation, debugging, terminal work, and code review.
- long-context research and knowledge work across documents, datasets, transcripts, repositories, spreadsheets, presentations, and operational materials.
- advanced agentic workflows that combine reasoning, tool calling, file search, web search, code execution, computer use, and structured outputs.
- cybersecurity and defensive engineering tasks such as secure code review, vulnerability triage, patch development, threat modeling, and validation in authorized contexts.
- scientific, technical, financial, legal, and business analysis where careful reasoning and high-quality synthesis matter more than lowest possible cost.
- design and frontend development tasks that require stronger layout judgment, visual hierarchy, interface refinement, and computer-use inspection.
How to Access GPT-5.6 Sol
How to access GPT-5.6 Sol
1. Official API
OpenAI lists GPT-5.6 Sol as gpt-5.6-sol in the API, with gpt-5.6 as an alias that routes to Sol. It supports Chat Completions, Responses, and Batch endpoints, text and image input, text output, streaming, function calling, structured outputs, and supported Responses API tools.
2. EssayDone AI Chat
EssayDone AI Chat provides access to this model through an easy-to-use chat interface when the model is available in the product.
This can be useful for complex writing, study, research, coding support, document analysis, and productivity tasks, but it does not replace the official API for developers who need direct endpoint, parameter, tool, or deployment control.
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FAQ
Here are some frequently asked questions about GPT-5.6 Sol.
Yes. GPT-5.6 Sol supports reasoning tokens and is listed by OpenAI with Highest reasoning capability. The GPT-5.6 family supports reasoning_effort settings of none, low, medium, high, xhigh, and max.
OpenAI lists GPT-5.6 Sol API pricing at $5.00 per 1M input tokens, $0.50 per 1M cached input tokens, and $30.00 per 1M output tokens. Prompts with more than 272K input tokens are priced at 2x input and 1.5x output for the full request, and cache writes are billed at 1.25x the uncached input token rate.
GPT-5.6 Sol is optimized for complex professional work, including coding, research, knowledge work, cybersecurity, science, computer use, design, long-context analysis, and advanced agent workflows.
GPT-5.6 Sol supports text and image inputs and returns text output. It can handle multimodal tasks such as screenshot analysis, visual document review, computer-use context, image-aware extraction, and visual reasoning, but audio and video are not supported modalities.
Compared with GPT-5.6 Terra, GPT-5.6 Sol is the higher-capability flagship model and costs more per token. Compared with GPT-5.6 Luna, Sol is designed for complex work rather than the fastest and lowest-cost high-volume workloads. GPT-5.6 Sol Pro is positioned separately as the highest-capability option for difficult tasks and longer-running workflows.
Using GPT-5.6 Sol in EssayDone AI Chat can provide a convenient way to use OpenAI's flagship GPT-5.6 model for complex writing, research, study, coding support, document analysis, and productivity tasks without setting up the API.