Cohesion
How much the things inside one module belong together. High cohesion means that when one part changes, the rest tend to change with it, and nothing unrelated gets dragged along.
An agent tends to add code wherever it is already looking, so a file can grow by convenience rather than by meaning. Low cohesion makes it read a lot to change a little, and that reading comes straight out of its context.
Say it to your agent
“src/utils.ts has become a drawer for everything. List what each export is for, group them by what changes together, move them to src/dates.ts and src/money.ts, and delete utils.ts when it is empty.”