Claude Fable 5.1 Now Generally Available in GitHub Copilot
GitHub CopilotGitHub Copilot made Claude Fable 5.1, Anthropic's latest Mythos-class model, generally available for long-horizon autonomous coding and knowledge-work tasks like deep codebase research and complex agentic workflows. It is rolling out gradually to Copilot Pro+, Max, Business, and Enterprise users across VS Code, Visual Studio, JetBrains IDEs, Xcode, Eclipse, github.com, and mobile, though Business and Enterprise admins must explicitly enable it since it is off by default. Unlike other Claude models in Copilot, Fable 5.1 requires data retention by default to run Anthropic's safety classifiers, with a time-bound zero-data-retention exemption available to eligible enterprises through year-end.
Key Takeaways
- GitHub Copilot made Claude Fable 5.1, Anthropic's newest Mythos-class model, generally available for long-horizon autonomous coding and research tasks.
- Independent benchmarks put Fable 5.1 ahead of Claude Opus 5 and its own predecessor Fable 5, while Anthropic prices it roughly 25% cheaper than Fable 5 for typical workloads.
- Access spans Copilot Pro+, Max, Business, and Enterprise, across VS Code, Visual Studio, JetBrains IDEs, Xcode, Eclipse, github.com, and mobile, with a gradual rollout.
- Business and Enterprise admins must explicitly enable the model policy, since it is off by default on those plans.
- Fable 5.1 requires data retention by default to power Anthropic's safety classifiers, unlike every other Claude model in Copilot, which runs zero data retention.
- Eligible enterprises get a time-bound zero-data-retention exemption through year-end while Anthropic rolls out its Enterprise Frontier Safeguards program.
Sources & Mentions
4 external resources covering this update
Anthropic upgrades Claude with new Fable 5.1 model, details here
9to5Mac
Anthropic Launches Claude Fable 5.1 With Lower Costs and Fewer False Positives
MacRumors
Anthropic's Claude Fable 5.1 promises better coding and research at up to 45 percent less
The Decoder
Claude Fable 5.1 (max with fallback): Intelligence, Performance & Price Analysis
Artificial Analysis
A New Frontier Model for Long-Running Agentic Work
GitHub Copilot has made Claude Fable 5.1, the newest model in Anthropic's Mythos class, generally available. Anthropic built Fable 5.1 specifically for long-horizon, autonomous coding and knowledge-work tasks, and GitHub's internal testing found it performs strongly on substantial, long-running coding work: deep codebase research, feature development, and complex agentic workflows that span many steps. Independent benchmarking has also placed Fable 5.1 ahead of its predecessor Fable 5 and of Claude Opus 5 on measures like the Vals Index, with Anthropic also pricing it roughly 25 percent cheaper than Fable 5 for typical workloads.
Where and Who Gets Access
Fable 5.1 is rolling out gradually to Copilot Pro+, Max, Business, and Enterprise subscribers, and it is landing across a wide set of surfaces: VS Code, Visual Studio, JetBrains IDEs, Xcode, Eclipse, github.com, and GitHub's mobile apps. Because rollout is staged, not every eligible developer will see the model appear in their picker on day one. Business and Enterprise administrators also need to take an explicit step, the model is disabled by default for those plans, so an admin has to turn on the Claude Fable 5.1 policy in Copilot settings before it becomes selectable for their teams. Billing follows standard usage-based pricing at the provider's list rate for the model.
A Data Retention Trade-Off
Fable 5.1 comes with a notable difference from other Claude models available in Copilot: it requires data retention by default in order to run Anthropic's safety classifiers. Anthropic keeps prompts and outputs from Fable 5.1 sessions for safety monitoring purposes, though it says that retained data is not used to train its models. Every other Claude model in Copilot continues to operate under zero data retention. For enterprises that need to avoid this trade-off, GitHub is offering a time-bound exemption: eligible enterprise customers can run Fable 5.1 with zero data retention through the end of the year while Anthropic finishes rolling out its Enterprise Frontier Safeguards program, after which continued zero-retention access will require that program's implementation. Interested enterprises are directed to contact their GitHub account team to check eligibility.