Tex. Local Government Code § 271.007

(a) If the governing body approves the contract and the contract provides for the payment of an aggregate amount of $100,000 or more, the governing body may submit the contract and the record relating to the contract to the attorney general for examination as to the validity of the contract. The attorney general shall approve the contract if it has been made in accordance with the constitution and other laws of this state, and the contract then shall be registered by the comptroller of public accounts.

(b) After the contract has been approved and registered as provided by this section, the contract is valid and is incontestable for any cause. The legal obligation of the lessor, vendor, or supplier of personal property or of the person installing personal property to the governmental agency is not diminished in any respect by the approval and registration of the contract.