task_snapshots gains via and read_at, an integer-bucket CHECK with a tombstone exception, the read-ordering rule in task_external_changes and the tasks_open view. task.missing names its task and a reason. Prototype rerun on Node 24.21.0 and 26.8.1; a mutant without the read_at rule reports the broker's own move as external. Lead decision 52 (B3). Co-Authored-By: Claude Opus 5.5 <[email protected]>