In short
How they differ.
Worked out from the figures below. Prices and specs are the makers' own, read Oct 20, 2026.
- Claude Sonnet 5.5 is cheaper per output token: $10 against $50 per million tokens, so GPT-6 Astra costs 5 times as much.
- GPT-6 Astra reads more at once: a context window of 1M tokens against 1M.
- On the 9 independent boards that rank both, GPT-6 Astra places higher on 5 and Claude Sonnet 5.5 on 4.
Side by side
The specs.
| Claude Sonnet 5.5 | GPT-6 Astra | |
|---|---|---|
| Made by | Anthropic · US | OpenAI · US |
| Released | Sep 28, 2026 | Sep 3, 2026 |
| Price per 1M tokens | $2 in / $10 out | $10 in / $50 out |
| Context window | 1M | 1M |
| Takes in | text, image | text, image |
| Download and run it yourself | No | No |
| Size | Not published | Not published |
| Maker says | “High-performance model for coding and agents” | “Our most capable model for the most demanding work.” |
| Sources | Prices, Oct 20, 2026 · Description | Prices, Oct 20, 2026 · Description |
Independent tests
Where they place.
Position on each board we follow (1 is best). Epoch AI's and Vectara's scores are shown; the other boards are linked for their own figures.
| Board | Claude Sonnet 5.5 | GPT-6 Astra |
|---|---|---|
| Epoch Capabilities IndexEpoch AI, Oct 20, 2026 | #6164.45 | #2166.41 |
| LMArena coding chatsLMArena, Oct 15, 2026 | Not listed | #9 |
| LMArena WebDevLMArena, Oct 19, 2026 | #3 | #2 |
| LMArena mathLMArena, Oct 15, 2026 | #15 | Not listed |
| LMArena documentsLMArena, Sep 13, 2026 | Not listed | #16 |
| LMArena Agent ArenaLMArena, Oct 19, 2026 | #5 | #2 |
| Humanity's Last ExamScale AI | #6 | #1 |
| SWE-Bench ProScale AI, Sep 22, 2026 | #8 | #5 |
| Remote Labor IndexScale AI | Not listed | #2 |
| Vals IndexVals AI, Oct 19, 2026 | #1 | #5 |
| Terminal-Bench 4.0Vals AI, Oct 19, 2026 | #2 | #3 |
| Vibe Code BenchVals AI, Oct 18, 2026 | #1 | #7 |
| ProofBenchVals AI, Oct 12, 2026 | #1 | #6 |
| CUA-bench (games)Vals AI, Oct 13, 2026 | Not listed | #1 |
| Vectara hallucination testVectara, Oct 16, 2026 | Not listed | #458.7% |
More comparisons