Building the Claude API for the Frontier: Inside Claude Platform's Release and Safety Decisions

Claude Platform engineers Jake Dejno and Lucca Siaudzionis explain how the Claude API evolves alongside each model launch, covering feature release decisions, model versioning and migrations, and cost management. They detail best practices for changing effort mid-conversation without breaking prompt caching, and how Claude Mythos and Fable share the same model weights with different safeguards. Claude Managed Agents and mid-conversation effort changes are in beta, and Mythos access runs through the Cyber Verification Program.