Quick answer
- Opus 5.5
- $4 in / $20 out per MTok
- GPT-6 Astra
- $10 in / $50 out per MTok
- Context
- 1M vs 1.05M
- Verified
- October 9, 2026 (Claude), September 30, 2026 (GPT-6)
Comparable facts
| Claude Opus 5.5 | GPT-6 Astra | |
|---|---|---|
| Base API price | $4 in / $20 out per MTok | $10 in / $50 out per MTok |
| Cached input | $0.20 | $1 |
| Context / output | 1M tokens (128K max output) | 1,050,000 tokens (128K max output) |
| Vendor position | Recommended Claude default | Highest-capability GPT-6 |
| Adaptive reasoning | Always on | Configurable; no none setting |
| Knowledge cutoff | June 2026 | April 30, 2026 |
| API model | claude-opus-5-5 | gpt-6-astra |
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Benchmark context
Anthropic's Claude Opus 5.5 launch table lists coding scores for both models, with the GPT-6 Astra figures marked as reported by OpenAI:
| Model | Terminal-Bench 4.0 | FrontierCode v1.1 | Input / output |
|---|---|---|---|
| Claude Opus 5.5 | 66.4% | 54.4% | $4/$20 |
| GPT-6 Astra | 57.9% | 53.3% | $10/$50 |
| Claude Fable 5.1 | 55.8% | 50.3% | $10/$50 |
Which one should you choose?
Pick Opus 5.5 if Claude Code is your primary agent or if $4/$20 better matches a sustained production workload. Pick Astra for an OpenAI-native stack or when maximum GPT-6 capability matters more than its $10/$50 list price. For the hardest Claude tasks, Anthropic's escalation path is Fable 5.1.
Astra is not OpenAI's everyday recommendation, though. For complex coding in Codex, OpenAI recommends GPT-6.1 Sol, which it describes as near-Astra performance at one fifth of Astra's token price ($2/$10, 5x less than Astra). If cost decides the OpenAI side, compare Opus 5.5 against 6.1 Sol on your own tasks; the Codex-side choice is in the best Codex model guide, and the vendor-level view in Claude vs GPT for coding.