Performing composable transactions in a dispersed storage network

A method for execution by a dispersed storage and task (DST) processing unit includes initializing a composite operation from a plurality of independent operations. An empty transaction context is created by performing an evaluation of the composite operation. A multi-source compare and swap (CASN) transaction is created from resulting expected values determined by evaluating the composite operation in the empty transaction context. The CASN transaction is executed against a dispersed storage network (DSN) memory. When the execution of the CASN transaction is successful, the transaction is committed to the DSN memory. When the execution failed due to at least one conflicting value stored in the DSN memory, a new transaction context pre-populated with the at least one conflicting value is created, and an updated CASN for the composite operation that utilizes the new transaction context is executed.