What a handoff must carry
A file can cross a boundary while understanding remains behind. A durable handoff carries the purpose of the work, the evidence behind the decision, the constraints that shaped it, and the person responsible for what comes next.
If one of those elements is absent, the receiving person has to rebuild context under time pressure. The resulting delay is usually blamed on communication even when the deeper problem is architecture.
Design the boundary
Begin by observing the real handoff, including exceptions and informal workarounds. Define the minimum context needed to act responsibly. Then choose the lightest mechanism that delivers that context at the moment it becomes useful.
A good boundary makes missing information visible. It does not manufacture certainty or hide an unresolved decision behind a completed status.