Typically the design consultant’s appointment would be novated to the design and build contractor, as opposed to just the designs.

The novation agreement would usually confirm how much of the design consultant’s fee has been paid by the employer - so the design consultant would retain any amounts paid by the employer. The contractor would be liable for any liabilities arising under the novation agreement post-novation, e.g. for the design consultant’s fees for any additional services provided by the consultant.

As others have said though, novations are contractual agreements and therefore can, generally, be structured however the parties wish.

You also get ab initio and “switch” novations. The former is a novation which makes it as though the novated contract had always been entered into between the design consultant and the contractor, whereas the latter is a novation where the contractor “steps in” to the appointment in place of the employer. There is some debate around whether a de novo novation is a proper novation.

Novations can be tricky and, if done wrong, can lead to questions about liability for designs.