GET /api/v1/accounts/{account_id}/human_ownership_policy returns the current revision or safe defaults at revision 0. GET /api/v1/accounts/{account_id}/human_ownership_policy/history returns up to 50 saved revisions, newest first, with the author and creation time. A departed or deleted author is returned as null.
POST /api/v1/accounts/{account_id}/human_ownership_policy appends a new revision and returns it with status 201. Omitted settings carry forward from the latest revision (or defaults); explicit null clears wait_trigger_minutes or alert_minutes. Even a no-op POST creates another revision. Past revisions cannot be updated or deleted through this API.
quiet_minutes accepts 15 through 10,080 (7 days; default 720). wait_trigger_minutes and alert_minutes accept 5 through 1,440 or null. auto_return and alert_enabled are booleans. return_mode is answer, answer_with_follow_up, or escalate. reason is optional, limited to 500 characters, and cannot contain a NUL byte. Alert recipients are positive user IDs belonging to the same account; repeated IDs are normalized, and at most 50 distinct members are stored.
An enabled alert requires alert_minutes. When both an alert and a wait trigger are set, alert_minutes must be less than wait_trigger_minutes. Invalid values or combinations return 422 and do not create a revision. Wrong field types return 422 with {"error":"invalid_params"}. If a carried-over recipient is no longer a member, the write returns stale_recipients; submit a fresh recipient list to continue.
The revision history is append-only. Revision events are outside this API contract and are owned by the later P5 event work.