What happens if the buyer's and seller's lawyers disagree about who holds the keys pending registration?

Who holds keys until registration or an undertaking is confirmed is a practical detail lawyers normally agree on before closing day, precisely to avoid a dispute like this arising in the moment. When there is disagreement, it usually comes down to which side is being asked to accept risk without adequate protection, since whoever releases keys before things are fully confirmed is effectively allowing possession to shift before the underlying legal transfer is fully secured.

In most cases, the practical resolution is for keys to be held, often by the listing brokerage or the seller's lawyer, until the buyer's lawyer confirms that funds have cleared and either registration is complete or a proper undertaking is in place covering the gap. If the two firms cannot agree in the moment, the safer default is to hold keys back rather than release them, since undoing a premature handover is much harder than briefly delaying it. This kind of disagreement is best avoided altogether by having your own lawyer confirm, before closing day, exactly what the plan for keys is going to be.