eshell-complex-commands

eshell-complex-commands is a variable defined in `esh-cmd.el'.
Its value is

("ls")

• This variable may be risky if used as a file-local variable.

Documentation:
A list of commands names or functions, that determine complexity.
That is, if a command is defined by a function named eshell/NAME,
and NAME is part of this list, it is invoked as a complex command.
Complex commands are always correct, but run much slower. If a
command works fine without being part of this list, then it doesn't
need to be.

If an entry is a function, it will be called with the name, and should
return non-nil if the command is complex.

You can customize this variable.