Could you give a concrete example of a situation you have in mind? If I'm understanding you correctly, then one solution could be to create a small wrapper to e

Could you give a concrete example of a situation you have in mind? If I'm understanding you correctly, then one solution could be to create a small wrapper to exec bash, source your environment-modifying script, and then exec fish. Are you familiar with exec [0]? fish also has an exec command [1]. I've been using fish for years and it hasn't been an issue. You can keep bash installed for any hardcore scripting, and just fish as your interactive shell. [0] https://stackoverflow.com/a/38581329 https://stackoverflow.com/a/38581329 [1] https://fishshell.com/docs/current/commands.html#exec https://fishshell.com/docs/current/commands.html#exec