Anthropic spotted testing unreleased Fable 5.2 in the wild; Opus 5.5 expected soon
testingcatalog · x · 2026-09-21
TestingCatalog reports that Anthropic appears to be quietly A/B testing its next frontier model in the wild, weeks after launching Claude Fable 5.1. Users on X have shared outputs believed to come from an unreleased Fable 5.2.
Key points:
- User Chetaslua got noticeably stronger responses to his usual prompts, concluding they came from a newer model; Anthropic hasn't commented on the rumored A/B test.
- Early clips show Fable 5.2 producing smooth interactive canvas animations, walking mascots and a ship-shooter game — all one-shot in pure JavaScript, with the demo video also made by the model and no external assets.
- Without being prompted, the model gave every animal in a scene its own customized snack.
- Opus 5.5 is expected soon as well.
Note: third-party report, unconfirmed by Anthropic.
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