In a distributed system that includes a debug server and debug clients coupled for data communications through a data communications network, where the server includes a debug administrator, a message router, a back-end debugger, and a debuggee, collaborative software debugging includes receiving, by the debug server, a plurality of application-level messages, including receiving, from a session owner, a request to enable a predefined operational mode; enabling the predefined operational mode; routing, by the message router in accordance with an application-level message passing protocol and in accordance with the enabled predefined operational mode, the application-level messages among the debug clients, the debug administrator, and the back-end debugger, including providing distributed control of the back-end debugger to the debug clients with application-level messages routed to the back-end debugger; and returning, by the debug server to the debug clients in response to the application-level messages routed to the back-end debugger, client-specific debug results.