Response field headers is no longer guaranteed

What changed

Producer-side tools call this non-breaking. For a consumer it is a null dereference on an unknown future date.

Affects result[].configuration.headers[key] on GET /accounts/{account_id}/workers/observability/destinations. Nothing fails at the call; it fails wherever the value is finally used, which is usually somewhere else entirely.

can now be null

Who is affected

Code that reads GET /accounts/{account_id}/workers/observability/destinations (result[].configuration.headers[key]).

Before and after

Code that breaks

// response.result[0].configuration.headers may now be absent or null
const headers = response.result[0].configuration.headers ?? fallback;

Based on Cloudflare’s published API specification. How severity is decided.