OnePassword can do something like this where you put references to a path there instead of the key material, and then you wrap the invoke command with their CLI

OnePassword can do something like this where you put references to a path there instead of the key material, and then you wrap the invoke command with their CLI and it replaces them. So your local env file never has anything sensitive. A malicious agent could still exfiltrate if you give it access to debug tools on the running code though.