GPT-6 Astra vs Claude Sonnet 5.5
GPT-6 Astra and Claude Sonnet 5.5 are within three points on the Models at Work leaderboard, which we treat as a tie (86 vs 84). Claude Sonnet 5.5 is about 5.0× cheaper per blended million tokens ($4 vs $20). On Artificial Analysis' independent Intelligence Index, Claude Sonnet 5.5 leads 56 to 53.
| GPT-6 Astra · OpenAI | Claude Sonnet 5.5 · Anthropic | |
|---|---|---|
| Leaderboard rank | #2 | #4 |
| Score (0–100) | 86 | 84 |
| Tier | Frontier | Workhorse |
| Price per 1M tokens | $10 in · $50 out | $2 in · $10 out |
| Context window | 1M | 1M |
| Open weights | No | No |
| Artificial Analysis Intelligence Index | 53 | 56 |
| Humanity's Last Exam, Diamond (Scale) | 60.6 | — |
| Humanity's Sixth Sense (Scale) | 53.6 | — |
| FrontierMath Erdős (Epoch) | 3% (2 of 68) | — |
| Best for | Hard reasoning, Research-grade analysis, When cost is not the constraint | Production coding assistants, High-volume agents, Default model for most teams |
Choose GPT-6 Astra if…
- you need hard reasoning
- you need research-grade analysis
- you need when cost is not the constraint
The reasoning heavyweight: leads the hardest exams and the cipher-cracking party tricks, and charges like it.
Caveats: Long-context pricing doubles above 272K input tokens. Speed is the lowest of the frontier set in Artificial Analysis' measurement.
Choose Claude Sonnet 5.5 if…
- you need production coding assistants
- you need high-volume agents
- you need default model for most teams
The value pick of the table: second on the index at a fifth of the Opus price, and the fastest of the top five.
What practitioners say
GPT-6 Astra: The launch drew the largest model thread of 2026 on Hacker News, and the stories that followed were about capability rather than cost: an Enigma message unsolved since 2005, a WWI cipher, a driving benchmark.
Claude Sonnet 5.5: Less discussed than its siblings because it just works; the October cache-read price cut to $0.10 per million was the news.
Questions people ask
Which is better, GPT-6 Astra or Claude Sonnet 5.5?
GPT-6 Astra and Claude Sonnet 5.5 are within three points on the Models at Work leaderboard, which we treat as a tie (86 vs 84). Claude Sonnet 5.5 is about 5.0× cheaper per blended million tokens ($4 vs $20). On Artificial Analysis' independent Intelligence Index, Claude Sonnet 5.5 leads 56 to 53.
When should I choose GPT-6 Astra over Claude Sonnet 5.5?
Choose GPT-6 Astra for hard reasoning, research-grade analysis, when cost is not the constraint. The reasoning heavyweight: leads the hardest exams and the cipher-cracking party tricks, and charges like it.
When should I choose Claude Sonnet 5.5 over GPT-6 Astra?
Choose Claude Sonnet 5.5 for production coding assistants, high-volume agents, default model for most teams. The value pick of the table: second on the index at a fifth of the Opus price, and the fastest of the top five.
Which is cheaper, GPT-6 Astra or Claude Sonnet 5.5?
GPT-6 Astra costs $10 per million input tokens and $50 per million output tokens on OpenAI's list price (OpenAI API pricing, read Oct 10, 2026). Claude Sonnet 5.5 costs $2 per million input tokens and $10 per million output tokens on Anthropic's list price (Claude pricing, read Oct 10, 2026).
Scores come from the Models at Work leaderboard: Score is 0 to 100: 50% independent evals normalised within this table, 20% price-performance, 15% practitioner sentiment from Signals and community threads, 15% operational fit (context, speed, availability, open weights). Models within three points are a tie in practice. Vendor-published figures are labelled as such and never counted as independent. Prices are vendor list prices where published; blended figures assume three input tokens per output token.