London Night Guide API Versioning & Deprecation Policy

The stability contract for the London Night Guide Content API (OpenAPI 3.1 spec). Agents can integrate against this surface knowing exactly how and when it changes.

Versioning

JSON endpoints are URL-path versioned: the current version is /api/v1/.
A breaking change ships as a new prefix (/api/v2/); it never mutates an existing version in place.
Within a version, changes are additive only: new endpoints and new response fields may appear, existing fields are never removed or retyped.
Unversioned content URLs (/{slug}/, .md paths, llms.txt, sitemap.xml, /feed/) are stable and follow the same additive-only rule.

Announcement — the deprecated operation is marked deprecated: true in openapi.json and noted on this page.
In-band signalling — every response from a deprecated endpoint carries a Deprecation header and a Sunset header (RFC 8594) with the retirement date.
Overlap — the old version keeps working for at least 90 days after the Sunset header first appears.
Retirement — after the sunset date the endpoint returns 404 with the standard JSON error envelope pointing at its replacement.

Treat a Deprecation or Sunset header on any response as the migration signal; the replacement endpoint is named on this page and in the spec.
Re-fetch /openapi.json periodically — the info.version field increments on every contract change.

Nothing. Every documented endpoint, including all of /api/v1/, is active with no planned sunset.

Questions about API stability: concierge@londonnightguide.com