Each step works in its own copy of your code, so agents cannot trip over each other. When the run ends, everything the agents changed waits on its own branch in your project. Nothing is pushed, and nothing reaches your own branch until you take it. If two branches really conflict when work is combined, the message names the branches where the work is kept. Files ignored by the project, such as build caches, are skipped, and step folders are removed when a run ends.
Two steps that would write to overlapping places at the same time are refused before the first process starts.