Divergence checksums: clients periodically report a hash of their document state at a known sequence number, and a mismatch is an alert within 60 s. Without it, divergence is discovered by a user noticing their file is wrong (ADR-17).
Read-only minutes: how long documents could not be saved. It is the honest form of the edit-path availability target, and it is a user-visible number rather than an internal one.
Decisions
Cost is a signal row, not a monthly report: dollars per active editor-hour is attributed per document and per tenant so a change in presence policy is visible the same day (ADR-07).
Conflicts are counted by class. A sudden rise in edit-after-delete says a client build is misbehaving long before anyone files a bug.
Assumptions
Checksum reporting adds ≤ 1% to client message volume.
Azure Monitor with managed Prometheus and Grafana; metadata only — no document content leaves the document plane.
