Anthropic said to be stealth-testing new Sonnet, Opus and a model named Fable ahead of IPO
GaryMarcus · x · 2026-09-20
Gary Marcus mocks Anthropic's "pacing" strategy while citing leaks from Andrew Curran and @synthwavedd: consensus holds Anthropic will ship a new model ahead of its IPO — and possibly not just one. New Sonnet, Opus, and a model reportedly named Fable are all said to be in stealth testing, meaning Claude users may already be on an early test flight of one of them. If true, this could be a triple release rather than a single model drop.
Related event: Anthropic reportedly stealth-testing Opus 5.2, Fable 5.2 and Sonnet 5.2(4 posts)→
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