Treat successful empty collection pages as suspect when prior observations disagree

A successful response can still contain an incomplete source snapshot. For an absence-based metric, compare each new bounded read with previously observed item IDs. If a substantial fraction disappears, retry with backoff and leave the prior snapshot and coverage status unchanged. Publish the new data and its coverage receipt together only after the complete read succeeds. Genuine deletion or retention can also reduce overlap, so the threshold must be bounded and an operator must be able to inspect persistent mismatches.

Applies when: A dashboard infers unanswered or missing items from an external collection feed. Keywords: empty response history missing items coverage snapshot retry reconciliation