Fable 5.1 edges Astra on every independent measure; list prices are tied

Asked:

compare astra to fable 5.1

Two frontier models — OpenAI GPT-6 Astra and Anthropic Claude Fable 5.1 — compared as of 8 September 2026: five official specification and price fields per model from OpenAI and Anthropic docs, one direct max-effort head-to-head from Artificial Analysis, and one separately reported Coding Agent Index result. Scores are index points; speed is tokens per second; prices are USD per million tokens.

Speed, latency and blended cost (Artificial Analysis, max effort)

Fable 5.1 leads the Intelligence Index 57 to 55 and the Coding Agent Index 70 to 67 — a modest edge, not a landslide, and configurations materially affect results. artificialanalysis.ai

Fable is quicker in operation: 68 vs 63 tokens/s output, first token in 272.3s vs 338.6s, and cheaper blended at $7.17 vs $7.70 per million tokens. artificialanalysis.ai

List prices are identical — $10 per million input tokens, $50 per million output — but Fable's cache-read price is $0.25 per million (2.5% of base input) versus Astra's $1, a 4x gap that favours cache-heavy, long-running agents. platform.claude.com

Astra offers a slightly larger context window, 1.05M vs 1M tokens; both cap output at 128K, and OpenAI positions Astra for computer use, browsing, research and document creation. developers.openai.com

Choose Fable 5.1 for

Demanding reasoning, coding agents, long-horizon agentic work, and cache-heavy workflows — it scores higher, responds faster, and cache reads cost a quarter as much.

Choose Astra for

Workflows built on OpenAI's ecosystem or its positioned strengths: computer use, browsing, research, cybersecurity, and document creation — with a marginally larger 1.05M context window.

Official specifications and prices

Model	Context window	Max output	Input $/M	Cached input $/M	Output $/M	Provider positioning	Source

Comparison of OpenAI GPT-6 Astra and Anthropic Claude Fable 5.1 as of 2026-09-08. Two specification rows from official OpenAI and Anthropic documentation; two benchmark rows: the Artificial Analysis head-to-head (GPT-6 Astra at max effort vs Claude Fable 5.1 with adaptive reasoning, max effort, default fallback) covering Intelligence Index points, output tokens/s, time to first token in seconds and blended USD per million tokens, and an AI Weekly report of Coding Agent Index scores. Benchmark values change as leaderboards and harnesses update; nothing was cut.

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