2100. The contractor and the provider of services are bound to act in the best interests of their client, with prudence and diligence. Depending on the nature of the work to be carried out or the service to be provided, they are also bound to act in accordance with usual practice and the rules of art, and, where applicable, to ensure that the work done or service provided is in conformity with the contract.
Where they are bound to produce results, they may not be relieved from liability except by proving superior force.