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Anthropic launches Claude Fable 5. 1 and Mythos 5. 1 models
Anthropic has released Claude Fable 5. 1 and Claude Mythos 5. 1, two versions of the same underlying model with different safety protocols. Fable 5. 1 is generally available for commercial use, while Mythos 5. 1 is restricted to vetted organizations in cybersecurity and life sciences.
The update focuses heavily on economic efficiency. While base token prices remain at $10 per million input and $50 per million output, Anthropic has reduced cache read costs by 75% to $0.25 per million tokens. This reduction is expected to lower typical workload costs by 25% and agentic task costs by up to 45%.
Performance improvements include higher scores in technical benchmarks, such as achieving 55.8% in Terminal-Bench 4. 0. The new models also feature more precise safety guardrails, reducing false positives in cybersecurity by approximately 60% and in biology by 85%. Additionally, Anthropic has introduced invisible watermarking for text and digital signatures for images to comply with regulations like the EU AI Act.
Entities
AWS · Amazon Bedrock · Amazon Web Services · Anthropic · Claude · Claude Fable 5. 1 · Claude Fable 5. 1 · Claude Fable 5.1 · Claude Mythos 5. 1 · Claude Mythos 5. 1 · Claude Mythos 5.1 · Google Cloud
Claims
What the coverage asserts, and how many sources carry each claim.
- [● 8 SOURCES] Mythos 5. 1 achieved a nearly 50% success rate in designing protein ligands in tests. www.mobilebit.com.br · www.ithome.com · www.mobiletime.com.br · www.fonearena.com · donanimgunlugu.com · +2 more
- [● 4 SOURCES] The company is rolling out a detection API for invisible watermarking in text. www.macrumors.com · www.ithome.com · the-decoder.de
- [● 35 SOURCES] Claude Fable 5. 1 reduces typical workload costs by approximately 25% and agentic task costs by up to 45%. brickinfotv.com · www.mobilebit.com.br · astig.ph · www.ithome.com · www.iclarified.com · +28 more
- [● 33 SOURCES] Claude Fable 5. 1 is generally available, while Mythos 5. 1 is restricted to vetted organizations in cybersecurity and life sciences. brickinfotv.com · www.mobilebit.com.br · www.elperiodico.digital · www.spacemoney.com.br · tech-ish.com · +26 more
- [● 8 SOURCES] Enterprise Frontier Safeguards (EFS) will allow customers to keep data on their own cloud infrastructure. brickinfotv.com · www.mobilebit.com.br · www.ithome.com · www.iclarified.com · cybersecuritynews.com · +2 more
- [● 35 SOURCES] Anthropic launched Claude Fable 5. 1 and Claude Mythos 5. 1 on September 1, 2026. brickinfotv.com · www.mobilebit.com.br · iosmac.es · www.elperiodico.digital · www.spacemoney.com.br · +28 more
- [● 31 SOURCES] Cache read pricing was reduced by 75% to $0.25 per million tokens. brickinfotv.com · www.mobilebit.com.br · astig.ph · www.ithome.com · www.iclarified.com · +24 more
- [● 25 SOURCES] Cybersecurity false positives in Claude Code are expected to decrease by approximately 60%. tech-ish.com · www.macrumors.com · www.ithome.com · www.iclarified.com · brickinfotv.com · +18 more
- [● 5 SOURCES] Fable 5. 1 scored 55.8% in Terminal-Bench 4. 0. ototekno.harianjogja.com · mayacomunicacion.com.mx · www.mobilebit.com.br · gadgetnews.net
- [○ 1 SOURCE] Anthropic is rolling out a detection API for invisible watermarking in text. www.itmedia.co.jp