Reject custody proof when the remote SHA-256 is absent or local hashing fails, and classify file enumeration failures as local client errors so their segments are quarantined instead of retried indefinitely. Make custody fixtures serve only their declared day, remove the unused capability path seam, and classify a wrong segments protocol version as incompatible. Extend regressions for missing SHA-256, literal missing custody, unstatable files, and day-specific triad queues.