BackendRefused

What a refusal says about the tree, for a caller that must tell the shape of a path from any other refusal (a composite listing a directory a mount makes): NotFound and NotADirectory; Corrupt for stored state the backend could not have written (another writer's), which a delete of the entry it names repairs; or Refused for anything else - a permission, a bound, an argument.

The names of the product elements

The name of the type

A refusal of the backend path path: its target is the path, and path says so, typed, so a composite rebases it through a mount. A target that is a key or a pattern has no path, whatever it looks like.

path is a file where a directory is needed.

path does not exist.

The tool outcome of a backend's error: a refusal is an Error the model sees; anything else - a store that failed, an effect whose outcome is unknown - is Fatal, so the task fails, commits nothing, and recover replays it from its replay records.