files.edit

Replace exact text inside a file without rewriting the whole file.

oldText is matched literally, never as a Luau pattern, and by default must appear exactly once — an edit that would hit several places is refused rather than applied to the wrong one. That refusal is the point of editing by anchor; pass replaceAll when every occurrence really is meant.

durable means what it means in files.write: while play is running, a durable edit becomes the source and survives play exiting.