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What is GPT-5.6 Terra?
GPT-5.6 Terra is a balanced OpenAI model in the GPT-5.6 family. OpenAI positions it for workloads that balance intelligence and cost, and notes that it roughly corresponds to the mini model tier used in earlier GPT-5 families.
Released for general availability on July 9, 2026, GPT-5.6 Terra is intended for everyday production work that needs stronger performance than low-cost high-volume models while avoiding flagship pricing. 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 Terra: Key Specs
Below are GPT-5.6 Terra's main specs and how they translate into real-world behavior.
- 1,050,000-token context window: GPT-5.6 Terra can process very large prompts, long documents, repository context, or retrieval bundles, which helps reduce chunking in production analysis workflows.
- 128,000 maximum output tokens: the model can generate long structured answers, reports, code plans, extracted datasets, and multi-section outputs when tasks require extended responses.
- Text and image input with text output: GPT-5.6 Terra can interpret written and visual context while returning text, supporting document review, screenshot analysis, visual data extraction, and multimodal workflow routing.
- Higher reasoning with reasoning token support: GPT-5.6 Terra can spend reasoning tokens on harder tasks, making it useful for agentic workflows, coding, structured analysis, and more complex decision support.
- $2.50 per 1M input tokens, $0.25 per 1M cached input tokens, and $15.00 per 1M output tokens: this pricing makes Terra a middle-tier GPT-5.6 option between Sol and Luna.
- Streaming, function calling, structured outputs, and Responses API tools: GPT-5.6 Terra 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 Terra, GPT-5.6 Sol & GPT-5.6 Luna
A brief overview of how each model differs in power, speed, and use cases.
| Feature | GPT-5.6 Terra | GPT-5.6 Sol | 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 | $2.50 input, $0.25 cached input, $15.00 output | $5.00 input, $0.50 cached input, $30.00 output | $1.00 input, $0.10 cached input, $6.00 output |
| Reasoning Performance | 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. | 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 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) | 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. | 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 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 | Production coding, structured data extraction, content workflows, general-purpose agents, long-context analysis, and cost-aware knowledge work | Complex reasoning, professional coding, long-context research, knowledge work, cybersecurity, science, computer use, design, and advanced agent workflows | High-volume classification, summarization, routing, structured extraction, real-time applications, coding support, and cost-sensitive agent workflows |
Best Cases to Use GPT-5.6 Terra
Best GPT-5.6 Terra use cases
- production coding workflows that need strong coding-agent performance without the higher cost of GPT-5.6 Sol.
- structured data extraction from documents, tickets, forms, screenshots, long files, and retrieval-augmented context bundles.
- general-purpose agentic tasks that combine reasoning, tool calling, file search, web search, code execution, and structured outputs.
- content workflows such as drafting, rewriting, summarizing, reviewing, and transforming long-form materials.
- business and knowledge-work analysis across large document sets, research notes, spreadsheets, presentations, and operational context.
- applications that need better capability than the lowest-cost model tier while preserving fast speed and predictable production pricing.
How to Access GPT-5.6 Terra
How to access GPT-5.6 Terra
1. Official API
OpenAI lists GPT-5.6 Terra as gpt-5.6-terra in the API. It supports Chat Completions and Responses 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 writing, study, research, summarization, coding support, document review, 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 Terra.
Yes. GPT-5.6 Terra supports reasoning tokens and is listed by OpenAI with Higher reasoning capability. The GPT-5.6 family supports reasoning_effort settings of none, low, medium, high, xhigh, and max.
OpenAI lists GPT-5.6 Terra API pricing at $2.50 per 1M input tokens, $0.25 per 1M cached input tokens, and $15.00 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 Terra is optimized for balanced production workloads, including code generation, content workflows, structured data extraction, long-context analysis, and general-purpose agentic tasks that need strong reasoning without flagship pricing.
GPT-5.6 Terra supports text and image inputs and returns text output. It can handle multimodal tasks such as screenshot analysis, document review, image-aware extraction, and visual context interpretation, but audio and video are not supported.
Compared with GPT-5.6 Sol, GPT-5.6 Terra is lower cost and positioned for balanced everyday production work rather than flagship capability. Compared with GPT-5.6 Luna, Terra costs more but is designed for broader capabilities and stronger overall performance. OpenAI describes Terra as roughly corresponding to the earlier mini tier.
Using GPT-5.6 Terra in EssayDone AI Chat can provide a convenient way to use a balanced OpenAI model for writing, research, study, coding support, document analysis, and productivity tasks without setting up the API.