Migrating a full client roster at once is how transitions fail. The wave structure we use instead.
The instinct when starting with a delivery partner is to move everything at once and get the pain over with. It is the wrong instinct, and it is how good arrangements collapse in week three.
Every account has an undocumented quirk — the client who only approves on Fridays, the conversion action nobody can explain, the landing page hosted somewhere strange. Moving one account surfaces one quirk at a time. Moving twelve surfaces twelve simultaneously, into a team that does not yet know your standards.
It also means every client experiences the transition in the same week, so any wobble is visible across your whole book at once.
Wave zero: the audit. No accounts move. We map what exists — accounts, properties, tags, access, and who actually owns each login. This routinely finds things that were broken long before anyone arrived.
Wave one: one account. Deliberately not your easiest and not your hardest. It runs the complete loop — brief, build, approve, report — so the process is tested end to end rather than in pieces.
Wave two: three to five. Enough to expose whether the process holds under parallel load.
Wave three onward: at your pace. Whatever your account managers can absorb without their week getting worse.
Client communication, without exception. The transition is exactly the wrong moment to change who your client hears from.
Send the shape of what you are carrying — how many accounts, which channels, where it hurts. We will come back with specifics.