Voice is the setting where latency is not a performance metric but a correctness one, because past a certain delay the human starts talking again and now you have an interruption to resolve rather than a slow reply. The number that decides whether an agent sounds human is usually not total round trip either, it is time to first audio - people forgive a slow sentence far more readily than a gap before anything happens. Worth measuring each hop separately, since in a stack like this the surprise is rarely the model: it is endpointing deciding the caller has finished when they merely paused, and every downstream stage inheriting that mistake. Barge-in handling is the other thing that separates demo from production, and it is much harder than the happy path suggests.