GPT-5.6 Terra or Claude Opus 5.5?
Choose GPT-5.6 Terra when balanced professional, coding and agent workloads is the closer match. Choose Claude Opus 5.5 when high-assurance software engineering, mathematical proofing and enterprise compliance matters more. Test both on the same real tasks before moving a production workflow.
Balanced professional, coding and agent workloads
High-assurance software engineering, mathematical proofing and enterprise compliance
GPT-5.6 Terra
GPT-5.6 model designed to balance intelligence and cost.
Official specification ↗Claude Opus 5.5
Anthropic's high-assurance flagship for formal verification, multi-repo coding and security audits.
Official specification ↗Side-by-side comparison
| Category | GPT-5.6 Terra | Claude Opus 5.5 |
|---|---|---|
| Provider | OpenAI | Anthropic |
| Type | Model · Reasoning model | Model · Frontier reasoning model |
| Pricing summary | $2 input, $0.20 cached input and $12 output per 1M tokens | $15 input, $1.50 cache read and $75 output per 1M tokens |
| Input price | $2 / 1M tokens | $15 / 1M tokens |
| Cached input | $0.20 / 1M tokens | $1.50 / 1M tokens |
| Output price | $12 / 1M tokens | $75 / 1M tokens |
| Context window | 1.05M tokens | 500K tokens |
| Maximum output | 128K tokens | 128K tokens |
| Knowledge cutoff | February 16, 2026 | August 2026 |
| Reasoning | none, low, medium, high, xhigh, max | Adaptive thinking with verifiable chains |
| Relative speed | Balanced | Deliberate / thorough |
| Input modalities | Text and image | Text and image |
| Output modalities | Text | Text |
| Tools and integrations | Functions, web search, file search, computer use and supported Responses API tools | Claude API tool use, computer use, Claude Code integration |
| API / access | v1/responses, v1/chat/completions and v1/batch | Claude Messages API |
| Best fit | Balanced professional, coding and agent workloads | High-assurance software engineering, mathematical proofing and enterprise compliance |
| Company | OpenAI | Anthropic |
| Product category | Model · Reasoning model | Model · Frontier reasoning model |
| Current pricing note | $2 input, $0.20 cached input and $12 output per 1M tokens | $15 input, $1.50 cache read and $75 output per 1M tokens |
| Best suited to | Balanced professional, coding and agent workloads | High-assurance software engineering, mathematical proofing and enterprise compliance |
| Key capabilities | 1.05M context; 128K maximum output; Vision input; Responses API tools | Formal logic verification; Multi-repo codebase refactoring; 500K context; Advanced computer use |
| Last verified | 2026-09-08 | 2026-10-28 |
| Official product source | https://developers.openai.com/api/docs/models/gpt-5.6-terra | https://platform.claude.com/docs/en/models/opus-5-5/overview |
How we reached this verdict
We looked at the things that affect everyday use: what each product can do, how its plans are structured, where it fits into your existing workflow, and what the provider currently documents. Benchmark results are useful context, but they are not a universal winner score because test settings and tools vary.
Common questions
GPT-5.6 Terra or Claude Opus 5.5: which should I choose?
Choose GPT-5.6 Terra for balanced professional, coding and agent workloads. Choose Claude Opus 5.5 for high-assurance software engineering, mathematical proofing and enterprise compliance. Validate the decision with your own prompts and total task cost.
Is GPT-5.6 Terra cheaper than Claude Opus 5.5?
Pricing units can differ. GPT-5.6 Terra: $2 input, $0.20 cached input and $12 output per 1M tokens. Claude Opus 5.5: $15 input, $1.50 cache read and $75 output per 1M tokens. Check tool charges, plan limits, caching and long-context rules before comparing totals.
Which is better for coding and agent work?
Capability depends on the selected product surface, tools and harness. GPT-5.6 Terra is positioned for balanced professional, coding and agent workloads; Claude Opus 5.5 is positioned for high-assurance software engineering, mathematical proofing and enterprise compliance. Run the same repository task on both.
How do their context windows compare?
GPT-5.6 Terra lists 1.05M tokens; Claude Opus 5.5 lists 500K tokens. A larger limit does not by itself guarantee better retrieval or lower cost.
Official sources
Use these provider pages to confirm current features, pricing and availability.
AI tools change quickly. We checked this page on 2026-09-08. Before you subscribe, confirm the latest price, regional availability and usage limits on the provider website.