Fable 5.1
A large language model that demonstrates strong performance on real-world engineering tasks, exhibiting practical capabilities in large-scale project builds that exceed what its benchmark scores alone would suggest.
Core Facts
The API model identifier for GPT-6 Astra is gpt-6-astra.
Opus 5.5 reaches the level of Fable 5.1 on most tasks, but with approximately 40% lower operating costs and faster speed.
On Automation Bench, Gemini 4 Argon scored 51.3%, surpassing Fable 5.1's 31.4% and Opus 5.5's 42.5%.
Timeline (last 90 days)
Aura offers a variety of frontier models to choose from, including GPT-6 Astra, Fable 5.1, and Opus 5.5, as well as a fully unrestricted automatic mode; users who have already used Claude Code can connect to Aura with one click.
On the Artificial Analysis composite intelligence index, Muse Wonderful ranked second at around 56 points, behind only Opus 5.5's 58 points, tied for second with Sonnet, above Fable 5.1, and leading GPT-6 Astra by about three points.
On the OS World benchmark, Muse Wonderful scored 78.4, Muse Wonder scored 72.6, Fable 5.1 scored 80, Astra scored 75, and Opus scored 81.
Muse Wonder and Muse Wonder Full were trained at the Prometheus data center, and their benchmark results are at the same level as Fable 5.1 and GPT-6 Astra.
In the advisor pairing mode, each 1 percentage point improvement in performance requires paying about 1.24 times more cost.
The current conclusion comes from only a single source, and whether the ratio of 1.7 points to 2.1 times cost holds stable across different task distributions still requires more independent replication.
Anthropic's internal testing showed that Fable 5.1 as an advisor paired with Opus 5.5 executing the main task improved performance by 1.7 percentage points compared with using Opus 5.5 alone, but increased cost by 2.1 times.
Opus 5.5 delivered a game of almost equivalent quality at less than half the cost of Fable 5.1, with the only minor flaw being that the putter follows the ball as it moves.
In a live test with a prompt to build a browser-based 3D mini golf game, Fable 5.1 took about 1 hour and 40 minutes and cost about 51 dollars.
Above Opus 5.5 there is a fourth model, Fable 5.1, priced at 10.5 dollars for output, aimed at the most demanding reasoning needs.
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All Facts (20)
The API model identifier for GPT-6 Astra is gpt-6-astra.
90%VerifiedOpus 5.5 reaches the level of Fable 5.1 on most tasks, but with approximately 40% lower operating costs and faster speed.
80%VerifiedOn Automation Bench, Gemini 4 Argon scored 51.3%, surpassing Fable 5.1's 31.4% and Opus 5.5's 42.5%.
70%VerifiedSonnet 5.5's cache read cost remained at $0.20 per million tokens with no reduction, whereas Fable 5.1 cut it by 90% and Opus cut it by approximately 60%.
65%VerifiedOn the DeepSuite benchmark, Grok 4.7 scored 71%, GPT 5.6 Sol scored 72.7%, Fable 5.1 scored 70%, and Astra Max topped the leaderboard at 74.1%.
65%VerifiedOn Terminal Bench 4.0, Opus 5.5 scored 66.4%, Astra scored 57.9%, Fable 5.1 scored 55.8%, and the previous generation Opus 5 scored 52.3%.
65%VerifiedClaude Opus 5's capabilities are close to the level of the previous-generation flagship Opus, but with significantly reduced inference costs.
65%VerifiedFable-5 is an AI agent framework based on the Claude model, with multi-step planning, tool invocation, and self-correction capabilities
65%Partially VerifiedFable 5.1 processed Venus radar photographs taken by NASA more than thirty years ago into clearer topographic maps.
65%UnverifiedFable 5.1 has stronger coding capabilities.
60%UnverifiedFable 5.1 is a large language model that supports multimodal input and tool calling.
60%UnverifiedFable 5.1 scored 52.6% on the Terminal Bench Science 0.1 benchmark, more than doubling the score of its previous generation.
60%UnverifiedAura offers a variety of frontier models to choose from, including GPT-6 Astra, Fable 5.1, and Opus 5.5, as well as a fully unrestricted automatic mode; users who have already used Claude Code can connect to Aura with one click.
50%UnverifiedOn the OS World benchmark, Muse Wonderful scored 78.4, Muse Wonder scored 72.6, Fable 5.1 scored 80, Astra scored 75, and Opus scored 81.
50%UnverifiedOn the Artificial Analysis composite intelligence index, Muse Wonderful ranked second at around 56 points, behind only Opus 5.5's 58 points, tied for second with Sonnet, above Fable 5.1, and leading GPT-6 Astra by about three points.
50%UnverifiedMuse Wonder and Muse Wonder Full were trained at the Prometheus data center, and their benchmark results are at the same level as Fable 5.1 and GPT-6 Astra.
50%UnverifiedAnthropic's internal testing showed that Fable 5.1 as an advisor paired with Opus 5.5 executing the main task improved performance by 1.7 percentage points compared with using Opus 5.5 alone, but increased cost by 2.1 times.
50%UnverifiedIn the advisor pairing mode, each 1 percentage point improvement in performance requires paying about 1.24 times more cost.
50%UnverifiedThe current conclusion comes from only a single source, and whether the ratio of 1.7 points to 2.1 times cost holds stable across different task distributions still requires more independent replication.
50%UnverifiedIn a live test with a prompt to build a browser-based 3D mini golf game, Fable 5.1 took about 1 hour and 40 minutes and cost about 51 dollars.
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