Coherence as a Deliverable: How a Multi-Surface Engagement Stays Sane

A sprawling multi-surface engagement (Kobiton partner pilot, 4 months, three deliverable rounds) exposed a silent failure mode: drift doesn't announce itself. A title rename on Plane goes unnoticed when the canonical source doc still has the old framing. A partner-portal deliverable gets updated before the source file does, leaving future sessions reading stale context from what should be source-of-truth. On 2026-05-08, one session caught two separate drift instances and shipped four structural...