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Claude Opus 5.5 vs GPT-6 Astra
The top general models from Anthropic and OpenAI right now. Astra is OpenAI's flagship; Opus 5.5 sits just below Anthropic's Fable tier but is priced far lower.
Side by side
| Opus 5.5 | GPT-6 Astra | |
|---|---|---|
| Vendor | Anthropic | OpenAI |
| Released | September 22, 2026 | September 4, 2026 |
| Input / output per 1M | $4.00 / $20.00 | $10.00 / $50.00 |
| Cached input per 1M | $0.20 | $1.00 |
| Context window | 1M | 1.05M |
| Coding agent | Claude Code | Codex |
Benchmarks
From Anthropic's Opus 5.5 launch post, which lists GPT-6 Astra alongside. OpenAI publishes its own comparisons, which can differ.
| Benchmark | Opus 5.5 | GPT-6 Astra |
|---|---|---|
| Terminal-Bench 4.0 | 66.4% | 57.9% |
| FrontierCode 1.1 | 54.4% | 53.3% |
| CursorBench 4.0 | 57.8% | — |
| AutomationBench | 40.0% | 41.4% |
| Humanity's Last Exam | 67.7% | 57.2% |
| OSWorld 2.1 | 81.8% | — |
OpenAI's own claim for its cheaper GPT-6.1 Sol: 2.2 points above Opus 5.5 on AutomationBench.
Source: Anthropic: Introducing Claude Opus 5.5
Cost per coding task
| Codebase size | Opus 5.5 | GPT-6 Astra |
|---|---|---|
| Small (< 10k lines) | $0.223 | $0.576 |
| Medium (10k-100k lines) | $0.498 | $1.290 |
| Large / monorepo (> 100k lines) | $1.188 | $3.090 |
At 173 tasks a month on a medium codebase: about $86 on Opus 5.5 and $223 on GPT-6 Astra.
Compare every model in the calculator
Which one to pick
- Terminal-heavy coding in an agent: Opus 5.5.
- Business-workflow automation across apps: Astra scored higher on AutomationBench, but GPT-6.1 Sol is much cheaper and OpenAI says it beats Opus 5.5 there.
- Tight budget: neither. Claude Sonnet 5.5 or GPT-6.1 Sol at $2 / $10.
FAQ
Is Opus 5.5 better than GPT-6?
On Anthropic's table, Opus 5.5 beat GPT-6 Astra on 3 of 4 shared benchmarks, including Terminal-Bench 4.0. Astra led on AutomationBench (41.4% vs 40.0%). Vendors pick benchmarks that suit them, so test on your own work.
Which is cheaper, Opus 5.5 or GPT-6 Astra?
Opus 5.5, at $4.00 / $20.00 per 1M tokens against $10.00 / $50.00.
Opus 5.5 vs GPT-6.1 Sol?
GPT-6.1 Sol costs half as much as Opus 5.5 ($2 / $10). OpenAI says it beats Opus 5.5 on AutomationBench; for coding agents, compare them on your own tasks.
Independent page, not affiliated with Anthropic or OpenAI. Benchmarks are vendor-published; we have not run our own tests.