Version conflict

What it means

Somebody changed the record between your read and your write. The body carries both versions so you can show a difference rather than a failure.

What to do

Re-read the record, reconcile the change with yours — showing the user both, if the fields overlap — and write again with the new ETag. Do not retry the same body; that is the edit you were about to lose, sent a second time.

The response

{
  "type": "https://casanova.realty/problems/version-conflict",
  "title": "Version conflict",
  "status": 409,
  "detail": "A sentence about this particular occurrence.",
  "instance": "/api/v1/properties/some-listing"
}

Content type is application/problem+json. Match on type, not on title — the title is prose and may be rewritten.