Chain of custody in an OCTAAR record is the same idea as chain of custody in an evidentiary context: every record points back to its source, its handler, its transformation, and the version of the standard against which it was assessed.
Observation, rubric version, scoring evaluator, calibration state at time of score, finding, action owner, due date, evidence, closure, and outcome are all linked. Personnel rotation does not break the chain. Rubric edits do not orphan historical scores.