Deprecation policy

How the Toggle TG-1 API versions and retires endpoints, and what an agent can rely on.

This page is the deprecation policy for the public API at https://fs-lp-toggletg.vercel.app. It exists so an agent can tell, without asking a person, how long a surface it integrates with will keep working.

Versioning

The API is versioned in the URL path. /v1 is the current version.
Additive changes, such as a new endpoint or a new response field, ship inside /v1 without a version bump.
Breaking changes ship under a new path, /v2.
/v1 keeps working for at least 12 months after /v2 ships.

How a deprecation is signalled

A deprecated route returns the header Deprecation: true on every response.
It also returns Sunset with an HTTP date, which is the earliest date the route can stop working.
The notice period is at least 90 days. No route is removed before its Sunset date.
The changelog on the docs page and llms.txt list the change, the replacement route and the sunset date.

What counts as breaking

Removing or renaming a response field, or changing its type.
Removing an endpoint, or changing its method or path.
Changing a status code a successful request returns, or changing the error shape.
Adding a required request parameter, or changing authentication.

What is not breaking

Adding a new endpoint.
Adding a new optional response field.
Adding a new optional query parameter.
Fixing a bug so a response matches the documented schema.

Current status

No route is deprecated. The last review was 1 November 2026. There is no Sunset date on any endpoint.

Contact

If a deprecation is unclear, email hello@fiftyseven.is with the endpoint and the date you saw the header. We answer within two business days.