Anthropic reportedly stealth-testing Opus 5.2, Fable 5.2 and Sonnet 5.2

Multiple sources suggest Anthropic is stealth-testing new Claude models including Opus 5.2, Fable 5.2 and Sonnet 5.2, with Gary Marcus mocking the company's pacing strategy amid speculation of a triple release before IPO.

2026-09-19 ~ 2026-09-20 · 4 related posts

• Leaks Claim Anthropic Stealth-Testing Fable 5.2, Opus 5.2 and Sonnet 5.2 — WorldofAI · 2026-09-19
• Rumor: Anthropic's Opus 5.2 and Fable 5.2 already tested, release may slip with IPO — kimmonismus · 2026-09-19
• Anthropic said to be stealth-testing new Sonnet, Opus and a model named Fable ahead of IPO — GaryMarcus · 2026-09-20

1 near-duplicate retellings: kimmonismus