The Short Version
This is the top-tier comparison, and the cheaper model wins more of it than you would expect. Opus 5.5 at $4 / $20 takes the coding benchmarks from Astra at $10 / $50. Astra takes computer use and long-horizon technical work.
Price
| Claude Opus 5.5 | GPT-6 Astra |
|---|
| Input / 1M | $4.00 | $10.00 |
| Output / 1M | $20.00 | $50.00 |
| Cached input / 1M | $0.20 | $1.00 |
| Batch input / output | $2 / $10 | not published |
| Context window | 1M | 1.05M |
The cache row is the widest gap: $0.20 against $1.00, five times. On a pipeline with heavy prompt reuse that ratio matters more than the headline prices do.
Benchmarks, Head to Head
| Benchmark | Opus 5.5 | GPT-6 Astra | Winner |
|---|
| Terminal-Bench 4.0 | 66.4% | 57.9% | Opus 5.5 by 8.5pp |
| FrontierCode v1.1 | 54.4% | 53.3% | Opus 5.5 by 1.1pp |
| AutomationBench | 40.0% | 41.4% | Astra by 1.4pp |
| Terminal-Bench-Science 0.1 | 58.7% | 64.6% | Astra by 5.9pp |
| OSWorld 2.0 | not reported | 73.5% | Astra, uncontested |
| DeepSWE v1.1 | not reported | 74.1% | Astra, uncontested |
What Terminal-Bench 4.0 Says
66.4% against 57.9% is the largest contested gap in this table, and it runs against price. Opus 5.5 is better at driving a terminal than a model costing two and a half times more.
If your agents work through a shell - running builds, reading logs, chaining commands, recovering from failures - this single row is the comparison. It is also the row most likely to describe real engineering work, as opposed to a benchmark harness.
What Astra Still Owns
OSWorld 2.0 at 73.5%. Anthropic did not publish an Opus 5.5 figure. For browser and desktop automation, Astra is the documented choice and Opus is an unknown you would have to measure yourself.
Terminal-Bench-Science at 64.6% against 58.7%. Long-horizon scientific and research workflows. A six-point gap on multi-hour tasks is substantial.
AutomationBench at 41.4% against 40.0%. Technically a win, practically a tie. Do not make a decision on 1.4 points.
The Honest Caveat From Anthropic
Anthropic said on launch that benchmark margins have become a less reliable guide to real-world differences at this capability level, and that the practical gap to Fable 5.1 is narrower than the published scores suggest.
Apply that to this comparison too. The 1.1 point FrontierCode win and the 1.4 point AutomationBench loss are noise. Terminal-Bench at 8.5 points and Terminal-Bench-Science at 5.9 are the only two gaps here large enough to act on.
Decision Framework
- Shell and terminal automation - Opus 5.5. Better and 60% cheaper. The clearest call in this comparison.
- Browser or desktop automation - Astra. 73.5% on OSWorld with no published Opus counterpart.
- Research and long-horizon scientific work - Astra, by 5.9 points on the benchmark built for it.
- General agentic coding - Opus 5.5. Same capability band, 60% less, and a cache read that costs a fifth as much.
- Cache-heavy production pipeline - Opus 5.5. $0.20 against $1.00 is where the money actually is.
- Budget is not the constraint and you want one model for everything - Astra covers more ground. You are paying a large premium for the two categories Opus does not report.
Verdict
Claude Opus 5.5 is the better default. It wins the terminal benchmark outright, ties on general coding, and costs 60% less with a cache read at a fifth the price. Move to GPT-6 Astra for computer use and long-horizon scientific work, where Astra either wins clearly or is the only one with a published number.