Claude Fable 5.1, the latest in @AnthropicAI's Mythos model class, is now generally available in GitHub Copilot. In our testing it showed strong performance on ➡️ long-running coding tasks ➡️ deep codebase research ➡️ complex agentic workflows Try it out in the GitHub Copilot app, CLI or @code. https://github.blog/changelog/2026-09-01…