Every team has one. Sometimes it is called utils.ts or helpers.py. Sometimes it has the name of a domain concept that originally meant something specific and has since absorbed everything tangentially related. The file is large enough that nobody opens it casually. It has multiple maintainers, each of whom understands a different third of it. New additions go into it because that is where similar things already live, and the file gets larger.
This is the god file: a single file that has grown to do too much, and that resists the refactor that would split it because the refactor is large and the file mostly works.
The god file is one of the most agent-hostile shapes a codebase can take.
How files get this big
No file is born five thousand lines long. The growth is incremental.
