Filesystem

The filesystem is the tree of files and directories an agent reads from, writes to, and runs things in. For a coding agent it is the default environment, and it is usually the thing the agent is worst at respecting.

Trees are deceptive. A path looks local and scoped but a glob can match ten thousand files, a symlink can point outside the project, and a path that seems safe can traverse upward. An agent that writes by pattern-matching on names will eventually overwrite something it was never shown.

The other property that bites is size. A directory listing can be enormous, a generated file can be megabytes, and a repository can contain history that dwarfs the working tree. Loading any of it wholesale fills the context with material that will never be relevant.

So the practical rules are: read before writing, match paths exactly rather than by pattern, and let the tooling summarise large directories instead of listing them. Most agent bugs that damage real work are path bugs, and they are all cheap to prevent.