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Claude Fable 5.1 made me a really nice animated pelican

Source: Simon Willison By Simon Willison
Image: Simon Willison

Today is Claude Fable (and Mythos) 5.1 day . Anthropic say that Fable 5.1 "sets a new standard for coding, knowledge work, and long-running problem-solving tasks". Their announcement spends a notable amount of time on scientific research, boasting of a 52.6% score on the brand new Terminal-Bench-Science 0.1 benchmark (first announced on August 27th ),…

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Anthropic released Claude Fable 5.1, a new AI model that sets a higher standard for coding, knowledge work, and long-running problem-solving. The model achieved a 52.6% score on the new Terminal-Bench-Science 0.1 benchmark, significantly outperforming competitors like Opus 5 and GPT-5.6 Sol. The release also includes five reasoning levels, allowing for fine-tuned task execution.

Why it matters

Why it matters: Anthropic's Fable 5.1 shows a substantial leap in scientific reasoning capabilities, evidenced by its strong performance on the new Terminal-Bench-Science benchmark. This positions it as a leader in AI for scientific research, potentially impacting academic and R&D sectors. While other benchmarks show incremental gains, the science score is a key differentiator against competitors like Google Gemini and OpenAI's GPT models. Future developments will likely focus on further refining scientific reasoning and exploring applications in complex problem-solving.

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Where the other five stand

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Hype check
4/5Big

Rated high: a launch, deal or policy change that changes what you can do or what it costs.

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Simon Willison (simonwillison.net)
Author
Simon Willison
Company
Anthropic · Web · Trade
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Claude Fable 5.1, Opus 5, GPT-5.6 Sol
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Subvolts, using an AI model (how we work). Spotted a mistake? Tell us.
#Benchmarks#Research#Coding#Models

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Questions people ask

What are the main improvements in Claude Fable 5.1?
Anthropic states Fable 5.1 sets a new standard for coding, knowledge work, and long-running problem-solving tasks. It also shows significant gains in scientific reasoning.
How does Fable 5.1 perform on scientific benchmarks?
Fable 5.1 scored 52.6% on the new Terminal-Bench-Science 0.1 benchmark, a notable increase from previous versions and competitors.
What reasoning options does Fable 5.1 offer?
Fable 5.1 provides five reasoning levels: low, medium, high, xhigh, and max. There is no option to turn reasoning off entirely.

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Page generated Sep 3, 2026. Summaries are Subvolts' own; the story belongs to Simon Willison.