Sep 1 2026
Anthropic releases Claude Fable 5.1 GA and Mythos 5.1 under verification-gated access; cache reads cut 75% to $0.25/M
MODELSAFETY
Original reporting
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Fable 5.1: 52.6% Terminal-Bench-Science (vs 24.7% for Fable 5), 55.8% Terminal-Bench 4.0, $10/$50 per million unchanged. Mythos 5.1 restricted to US organizations vetted through new Cyber and Life Sciences Verification Programs. ARC Prize verified 90.0% on the same day.
Named in this event
Anthropic
Open calls that touch this
- Anthropic holds the Sonnet 5 price increase · 70%, resolves November 30th 2026
- Anthropic IPOs before OpenAI · 75%, resolves August 6th 2027
- Anthropic keeps Model 2 unreleased through February 2027 · 70%, resolves March 1st 2027
- A second flagship API adopts time-of-day pricing · 55%, resolves February 17th 2027
- Anthropic runs no production traffic on Fractile silicon in 2027 · 70%, resolves December 31st 2027
- Broadcom's Anthropic chip financing closes at $60 billion or more · 65%, resolves June 30th 2027
Issues that mention Anthropic
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