What is the standard of review in cases involving "cooperation agreements"?

"The standard of review in cases involving 'cooperation' agreements depends on the issue raised. . . . [W]hether a party carried through with its part of the agreement generally is a question of fact reviewed under the substantial evidence standard. [Citations.] [] However, when a cooperation agreement embraces a promise to dismiss or reduce charges, whether the promise is authorized and enforceable usually is a legal question reviewed de novo. [Citations.]" (People v. C.S.A. (2010) 181 Cal.App.4th 773, 777-778 (C.S.A.).)