A machine vision system program editing environment includes near real time context generation. Rather than requiring execution of all preceding instructions of a part program in order to generate a realistic context for subsequent edits, surrogate data operations using previously saved data replace execution of certain sets of instructions. The surrogate data may be saved during the actual execution of operations that are recorded in a part program. An edit mode of execution substitutes that data as a surrogate for executing the operations that would otherwise generate that data. Significant time savings may be achieved for context generation, such that editing occurs within an operating context which may be repeatedly refreshed for accuracy in near real time. This supports convenient program modification by relatively unskilled users, using the native user interface of the machine vision system, rather than difficult to use text-based or graphical object-based editing environments.