Stated negative: identical price, Fable 5.1 leads both independent indices
GPT-6: Astra and Claude Fable 5.1 both list at $10 per 1M input and $50 per 1M output tokens. At that identical price, Claude Fable 5.1 currently scores higher on both Artificial Analysis composites: Intelligence Index 66 against 61, and Coding Agent Index 70 against 67. A page that only cites Astra's wins would not be a comparison page.
Independent index scoreboard
Both figures come from Artificial Analysis, an independent third party, not from either vendor.
| Index | GPT-6: Astra | Claude Fable 5.1 | Delta |
|---|---|---|---|
| Intelligence Index | 61 | 66 | Fable +5 |
| Coding Agent Index | 67 | 70 | Fable +3 |
Price and cache economics
List price is identical, but the two diverge sharply on cached input: Claude Fable 5.1 reads cache at $0.25 per 1M tokens; GPT-6: Astra reads cache at $1.00 per 1M, four times more. On a cache-heavy agent this compounds well beyond the headline price parity.
| Dimension | GPT-6: Astra | Claude Fable 5.1 |
|---|---|---|
| Input $/1M | $10.00 | $10.00 |
| Output $/1M | $50.00 | $50.00 |
| Cached input $/1M | $1.00 | $0.25 |
| Context window | 1,050,000 | 1,000,000 |
| Max output tokens | 128,000 | 128,000 |
| Input modalities | Text, image | Text, image, file |
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Create account & add creditsWhere Astra is ahead on OpenAI's own numbers
On OpenAI's vendor-reported tables, GPT-6: Astra posts strong scores on FrontierMath Tier 4 (v2) at 97.6% and ExploitBench at 100.0%. Anthropic has not published matching runs on those exact evaluations for Claude Fable 5.1, so this is not a head-to-head; it states what OpenAI reported for its own model.
When to pick which
Pick Claude Fable 5.1 when the workload is cache-heavy (the $0.25 read rate compounds fast) or when the independent composite scores matter more than any single vendor benchmark. Pick GPT-6: Astra when you specifically need its 1,050,000-token context ceiling, image input alongside text, or one of the OpenAI-specific evaluations where it scores strongly.
Frequently asked questions
Is GPT-6: Astra better than Claude Fable 5.1?
Not on the independent Artificial Analysis composites: at an identical $10/$50 per 1M list price, Claude Fable 5.1 scores 66 to Astra's 61 on the Intelligence Index and 70 to 67 on the Coding Agent Index. Astra leads on some of OpenAI's own vendor-reported evaluations, such as FrontierMath Tier 4 (v2), but those have not been run head-to-head against Fable 5.1.
Which is cheaper, GPT-6: Astra or Claude Fable 5.1?
List price is identical at $10 per 1M input and $50 per 1M output. Claude Fable 5.1 is cheaper on cached input, at $0.25 per 1M against $1.00 for GPT-6: Astra, so a cache-heavy workload costs meaningfully less on Fable 5.1 despite the matching headline rate.
Put GPT-6: Astra to work
Fund a controlled evaluation, start with a prepared prompt, and measure quality and cost on your own workload.