Why it is harder than it looksConsistency is a knowledge architecture, not a coat of paint.
Every channel evolved separately. The phone desk, the mailbox, the portal and the apps each grew their own logic and their own view of the customer - which orders they see, which terms they trust, which notes they keep. Ask the same question in two places and you can get two answers, both delivered with confidence.
So "the same answer everywhere" is not a UI problem. Putting the same assistant skin on four channels gives you four assistants that disagree in the same font. What it takes is one governed source of account truth that every channel reads - and writes back to - so the context survives the switch.
It also takes agent behavior that holds still. An answer that drifts per channel, or shifts every time a model updates underneath, recreates the original problem with better grammar. The governed context and the pinned behavior are the real work; the channel interfaces are the easy part.