Simon Willison’s Weblog
Anthropic released Fable 5.2 and Mythos 5.2 today. Fable 5.2 is currently ranked first on Artificial Analysis . Anthropic say it "solved two open problems in the physics of black holes", so clearly their internal benchmarks have become more ambitious!
I've added the new models to llm-anthropic , so you can now run prompts through Fable 5.2 like this:
uv tool install llm llm install llm-anthropic llm keys set anthropic # paste key here llm -m claude-fable-5.2 "Generate an SVG of a pelican riding a bicycle"
I ran pelicans at all five reasoning levels - low , medium , high , xhigh , and max . You can see them all here - here's the best result I got, from xhigh :
max failed to return an image at all, running out of tokens after spending 128,000 thinking about them . That's the same bug that I saw with Opus 5.5 - but it's new for the Fable series, both Fable 5 and Fable 5.1 returned max effort pelicans just fine.
It's priced at $8/million input and $40/million output, which is a 20% discount on the previous Fable 5.1 ($10/$50).
I also used Fable 5.2 to help identify the source of a mysterious beep .
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This is a beat by Simon Willison, posted on 9th November 2026 .
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