Yannis API versioning

The current yannis.dev public REST surface is version 1. JSON responses include the Yannis-API-Version: 1 response header, and OpenAPI documents the same header as an optional request parameter for clients that want to pin the version they have tested.

Version 1 covers the read-only status endpoint, OpenAPI document, MCP discovery JSON, and related agent resources. HTML pages and markdown twins are content resources, but they are listed in the same OpenAPI document so agents can discover them from one place.

Breaking changes will use a new version value before they replace the current contract. The existing version stays available for at least 90 days after the new contract is documented. If an endpoint is scheduled to stop responding, the API will publish the Sunset HTTP header with an HTTP-date and link back to this policy from the OpenAPI description.

No public endpoint is deprecated right now. Clients should treat missing Sunset headers as no scheduled retirement, not as a lifetime guarantee. For product decisions or private integrations that need stronger guarantees, email hello@yannis.dev .