GPT-6 Astra vs Claude Sonnet 5.5
Claude Sonnet 5.5 comes out ahead, 72 to 68 on our weighted score, and it is the cheaper option too.
OpenAIGPT-6 Astra
68/100- ECI166.5
- Price$10.00 / $50.00
- Context1.05M
- Our pick
AnthropicClaude Sonnet 5.5
72/100- ECI165.2
- Price$2.00 / $10.00
- Context1M
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Make it a three-way comparison.
Claude Sonnet 5.5 is our pick
Claude Sonnet 5.5 is the better all-round choice, scoring 72/100 against GPT-6 Astra (68). It leads on price. GPT-6 Astra wins on capability. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.
- CapabilityGPT-6 AstraCapabilities Index (ECI): GPT-6 Astra 166.5 · Claude Sonnet 5.5 165.2
- Lowest priceClaude Sonnet 5.5Claude Sonnet 5.5 $4.00 · GPT-6 Astra $20.00 per 1M tokens (3:1 blend)
- Longest contextGPT-6 AstraGPT-6 Astra 1,050,000 · Claude Sonnet 5.5 1,000,000 tokens
- Widest inputsSame inputsGPT-6 Astra: Text, Images, PDFs · Claude Sonnet 5.5: Text, Images, PDFs
- Self-hostingNo open weightsBoth are available only through APIs
| Measure | Weight | GPT-6 Astra | Claude Sonnet 5.5 |
|---|---|---|---|
| CapabilityCapabilities Index (ECI) | 50% | 99 | 97 |
| Price | 25% | 0 | 21 |
| Inputs & features | 15% | 80 | 80 |
| Context window | 10% | 61 | 60 |
| Overall | 100% | 68/100 | 72/100 |
Every spec in one table
Highlighted cells lead their row. Dashes mean the data is not published.
| Specification | GPT-6 AstraOpenAI | Claude Sonnet 5.5Anthropic |
|---|---|---|
| Capability | ||
| Capabilities Index (ECI) | 166.5 (best) | 165.2 |
| ECI rank | #2 of 148 (best) | #3 of 148 |
| GPQA DiamondGraduate-level science questions | 95.8% (best) | 95.6% |
| FrontierMath Tiers 1–3Research-level mathematics | 93.7% (best) | 88.8% |
| OTIS Mock AIME 2024–2025Competition mathematics | 100% | 100% |
| SimpleQA VerifiedShort factual questions | 75.6% (best) | 46.5% |
| Price per million tokens | ||
| Input | $10.00 | $2.00 (best) |
| Output | $50.00 | $10.00 (best) |
| Cached input | $1.00 | $0.20 (best) |
| Blended (3:1) | $20.00 | $4.00 (best) |
| Long-context rate | Over 272K: $20.00 / $75.00 | Same rate |
| Price source | Official OpenAI API | Official Anthropic API |
| Limits | ||
| Context window | 1,050,000 tokens (best) | 1,000,000 tokens |
| Max output | 128,000 tokens | 128,000 tokens |
| Inputs and features | ||
| Text | Yes | Yes |
| Images | Yes | Yes |
| PDFs | Yes | Yes |
| Audio | No | No |
| Video | No | No |
| Reasoning | Yeslow · medium · high · xhigh · max | Yeslow · medium · high · xhigh · max |
| Tool calling | Yes | Yes |
| Structured output | Yes | Yes |
| Availability | ||
| Weights | Proprietary | Proprietary |
| API model ID | gpt-6-astra | claude-sonnet-5-5 |
| API providers | 26 (best) | 23 |
| Released | Sep 4, 2026 | Sep 28, 2026 |
| Knowledge cutoff | Apr 30, 2026 | Jun 2026 |
What would a month cost?
Enter your expected volume in millions of tokens. List prices only; caching and batch discounts would lower these.
- GPT-6 Astra$200.00
- Claude Sonnet 5.5$40.00
Which should you choose?
Which is better: GPT-6 Astra or Claude Sonnet 5.5?
Claude Sonnet 5.5 is the better all-round choice, scoring 72/100 against GPT-6 Astra (68). It leads on price. GPT-6 Astra wins on capability. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.
Which is cheaper, GPT-6 Astra or Claude Sonnet 5.5?
Claude Sonnet 5.5 is cheaper at $2.00 input / $10.00 output per million tokens (official Anthropic API price). GPT-6 Astra costs $10.00 input / $50.00 output per million tokens (official OpenAI API price). At a typical mix of three input tokens to one output token, that is $4.00 per million tokens for Claude Sonnet 5.5 versus $20.00 for GPT-6 Astra (5× as much).
Which scores higher on benchmarks?
GPT-6 Astra scores higher on the Capabilities Index (ECI): GPT-6 Astra 166.5 (#2 of 148) and Claude Sonnet 5.5 165.2 (#3 of 148). The confidence ranges of the top two overlap (163.1–171.1 vs 161.8–169.4), so treat the gap as small. On individual benchmarks: GPQA Diamond — GPT-6 Astra 95.8%, Claude Sonnet 5.5 95.6%; FrontierMath Tiers 1–3 — GPT-6 Astra 93.7%, Claude Sonnet 5.5 88.8%; OTIS Mock AIME 2024–2025 — GPT-6 Astra 100%, Claude Sonnet 5.5 100%; SimpleQA Verified — GPT-6 Astra 75.6%, Claude Sonnet 5.5 46.5%.
Which is better for coding?
There are no published SWE-bench Verified results for GPT-6 Astra and Claude Sonnet 5.5 yet, so there is no like-for-like coding score. On overall capability, GPT-6 Astra leads, which tends to carry over to coding, but test on your own codebase. Both support tool calling for agent workflows.
Which has the bigger context window?
GPT-6 Astra has the largest context window at 1,050,000 tokens, against 1,000,000 for Claude Sonnet 5.5. Maximum output per response: GPT-6 Astra up to 128,000, Claude Sonnet 5.5 up to 128,000 tokens.
Which can read images, PDFs, audio or video?
GPT-6 Astra accepts text, images and PDFs; Claude Sonnet 5.5 accepts text, images and PDFs. They handle the same number of input types.
Are any of these open source?
No. GPT-6 Astra and Claude Sonnet 5.5 are proprietary and only available through APIs and apps.
Which is newer?
Claude Sonnet 5.5 is the newest, released Sep 28, 2026. GPT-6 Astra came out Sep 4, 2026. Knowledge cutoff: GPT-6 Astra Apr 30, 2026, Claude Sonnet 5.5 Jun 2026.
How do you decide the winner?
Each model gets a 0–100 score on capability (50%, independent benchmark results); price (25%, blended price per million tokens (3 input : 1 output), log scale); inputs & features (15%, image, PDF, audio and video input, tool calling, structured output and reasoning); context window (10%, maximum tokens per request, log scale). Dimensions missing for any model are dropped and the remaining weights rescaled, so every model is judged on the same evidence. Specs and prices come from public model listings and the labs’ own API pages; capability scores come from independent benchmark runs. Data updated Oct 4, 2026.
