Claude Fable 5.1 Now Generally Available in GitHub Copilot

GitHub announced that Claude Fable 5.1 from Anthropic is generally available in Copilot. The company described it as the latest model in the Mythos class and noted strong performance during internal testing on long-running coding tasks, deep codebase research, and complex agentic workflows. Access is available in the Copilot app, CLI, and VS Code. The linked changelog states the model targets long-horizon autonomous coding and knowledge-work tasks.