California Code, Public Contract Code - PCC § 20463

The bond shall guarantee the payment of any sum which the claimant may recover on the claim together with his costs of suit in the action, if he shall recover therein. If such bond is filed, the city, any officer thereof, or superintendent of streets shall not withhold any moneys or funds, assessment, partial assessment, any reassessment and any bonds which may be issued to represent any assessment or reassessment from the contractor on account of the claim. The sureties upon the bond shall be jointly and severally liable to the claimant with the sureties upon the contractor's original labor and material bond posted by the contractor.