Anthropic launches Claude Fable 5.1 and says it’s up to 45 percent cheaper for agentic work

Anthropic launched Claude Fable 5.1 across its platforms and Mythos 5.1 for Project Glasswing participants. The company says Fable 5.1 is stronger than Fable 5, typically about 25 percent cheaper, and up to 45 percent cheaper on complex agentic tasks because of lower prices on cached data already processed and stored.

That is a customer-ticket release. The Verge notes the models are aimed at complaints about price, data retention, and overzealous safeguards. Enterprise Frontier Safeguards, due later this fall, store data on the customer's cloud rather than Anthropic's and are sold as 'complete privacy.'

Price is the headline because agent workloads burn tokens. A cache discount that can reach 45 percent is how you keep a coding agent online without a CFO intervention. It is not the same as a 45 percent cut on every call. Anyone who quotes the high number without 'cached, agentic' is doing marketing.

The early-access quotes are the usual friendly chorus. Dan Shipper called it the strongest coding model Every has used, now fast and 'speaks like a normal person.' Aaron Levie said a Box agent caught subtleties Fable 5 missed on the same test. A user posted that Mythos 5.1 on low reasoning matched the prior model on Max. Treat those as directional. They are not a bakeoff.

Safeguards are the cultural tell. Fable 5.1 has 'more precise' filters that Anthropic says are less likely to block basic biology questions; Mythos 5.1 keeps the old biology restrictions. Anthropic is also letting Fable 5.1 identify software vulnerabilities, while still sending penetration testing, exploit generation, and binary scanning to Opus. That is a product manager drawing a line the safety team can live with and the security buyer can still use.

Signal Desk's read: this is Anthropic competing on cost-to-complete-a-task and on enterprise data gravity, not on a new capability class. If Frontier Safeguards actually keep prompts off Anthropic disks, that is the feature regulated buyers have been waiting for. If it is a contractual label on the same logs, the 45 percent will be the only thing that ships.

Project Glasswing is Anthropic's limited access track for Mythos 5.1. Opus remains the sink for the sharper cyber tasks. The release sits in a week when OpenAI is absorbing lawsuit and delay news, which makes a cheaper, less naggy Claude an easy switch pitch.