Doc page: https://docs.vyos.io/en/latest/automation/vyos-api.html

{"op":"save"} POSTed to /configure returns HTTP 400 — "Malformed command … missing 'path' field". Persisting the config requires POSTing {"op":"save"} to /config-file instead.

The docs do document save under /config-file, but nothing on the /configure section warns that it rejects save — and since all set/delete traffic already flows through /configure, sending the save there is the natural (wrong) first attempt for API users. We hit this in automation on VyOS 1.5 rolling.

Suggested one-line doc addition to the /configure section: "Persistence: to save the running config to disk, use /config-file with {"op":"save"} — /configure does not accept the save op."