Anthropic has released Claude Fable 5.1, a generally available model for coding and knowledge work, and Claude Mythos 5.1, which it says is currently limited to a set of US organisations.
The company dated the announcement 1 September 2026, with no clock time. It says the two are the same underlying model with different safeguards.
Claude Fable 5.1: price, plans and where it runs
The Claude Fable product page lists Claude Fable 5.1 for Pro, Max, Team and Enterprise users. Developers can call it on the Claude API as claude-fable-5-1. Anthropic does not say whether a free or Core tier gets the model, so that availability is omitted here.
Input and output prices match Fable 5: $10 per million input tokens and $50 per million output tokens. Cache reads now cost $0.25 per million tokens, 75% less than Fable 5. Anthropic estimates that cuts typical token-billed workloads by around 25%, and highly agentic work by up to about 45%.
Fable 5.1 is listed as available today on Amazon Web Services, Google Cloud and Microsoft Azure. The product page also names the Claude Platform, available marketplaces, and Microsoft Foundry. In Claude Code, Anthropic says the model defaults to High effort; on Claude Cowork and Claude.ai it defaults to Medium.
What UAE users can actually use
Anthropic’s supported-countries list includes the United Arab Emirates for both Claude.ai and commercial API access. Fable 5.1 is described as generally available on the paid plans above. Anthropic has not posted a UAE-specific Fable 5.1 notice.
Claude Mythos 5.1 is narrower. The announcement says it is currently available only to a set of US organisations, with Anthropic coordinating with the US government to expand access to a broader set of domestic and international partners. UAE access to Mythos 5.1 is unconfirmed.
Anthropic previously disabled Fable 5 and Mythos 5 worldwide in June after a US government order. The Fable product page records that Fable 5 access was restored on 1 July 2026. Today’s 5.1 release is a new version, not a regional exception.
Fable, Mythos and the new safeguards
Anthropic positions Fable 5.1 as its most capable generally available model for long-running coding and knowledge work. Mythos 5.1 is the same model with more permissive safeguards for vetted cyberdefence and life-sciences work, through trusted access programmes. Claude Security, Anthropic’s codebase scanner, now also runs on Mythos 5.1.
On Fable 5.1, Anthropic says cybersecurity safeguards now allow the model to identify software vulnerabilities in source code, while still blocking penetration testing, exploit generation and binary-based vulnerability scanning. It reports around 60% fewer cyber-safeguard interventions per Claude Code session than on Fable 5. Biology safeguards, it says, fire 85% less often on benign elementary biology and medical questions; research-and-development life-sciences queries are still routed to Opus models.
Official scores, with production safeguards on, include 52.6% on Terminal-Bench-Science 0.1 (Fable 5: 24.7%), 55.8% on Terminal-Bench 4.0 (Mythos 5.1: 60.9%; Fable 5: 42.0%), and 73.4% on CursorBench 3.2.0 (Fable 5: 70.5%). Anthropic also reports that Mythos 5.1 designed protein binders that external organisations then confirmed to bind in the lab.
Enterprise Frontier Safeguards, which let customers store data on their own cloud rather than Anthropic’s, is rolling out in phases from this autumn. Until then, eligible customers can use Fable 5.1 with zero data retention.
Claude Fable 5.1 is listed as available today on Pro, Max, Team and Enterprise, and on the Claude API as claude-fable-5-1. Mythos 5.1 remains limited to a set of US organisations; Anthropic has not confirmed UAE access.
