Can confirm that the linked code does not work locally as of now. On typing “ech” and then clicking Tab once, no autocompletion is registered. On clicking Tab twice, I get back multiple completions:
The reason is you are concatenating both the built-in commands and the executables found in the PATH as a slice to get all possible completions. This breaks things, as echo is both an executable in the tester’s PATH, as well as a built-in command we have implemented in the previous stages. Deduplicating the commands should fix the same.