Backward compatibility

Jan is committed to providing stability to API users by avoiding breaking changes in major API versions whenever reasonably possible. This includes:

• The REST API (currently v1)
• OpenAI SDK compatibility
• Model families

Model prompting behavior between snapshots is subject to change.

Model outputs are by their nature variable, so expect changes in prompting and model behavior between snapshots. For example, if you moved from one model or snapshot version to another, the same system or user messages could function differently between versions. The best way to ensure consistent prompting behavior and model output is to use pinned model versions, and to implement evals for your applications.

Backwards-compatible API changes:

• Adding new resources (URLs) to the REST API
• Adding new optional API parameters
• Adding new properties to JSON response objects or event data
• Changing the order of properties in a JSON response object
• Changing the length or format of opaque strings, like resource identifiers and UUIDs
• Adding new event types (in either streaming or the Realtime API)

See the changelog for a list of backwards-compatible changes and rare breaking changes.