Those files accessed by tools during a build process are invisibly tracked in such a way that the information can then be used to drive an incremental build of just enough files to bring the build fully up to date. The tracking information includes the association between distinct tool processes. Each build tool has its own file activity tracked, each thread of operation within tools are tracked separately and a tracking log is associated with a chain of tool processes so that when the tracking logs are interpreted the context in which they were created is preserved.