First though is that its the alias in the .dir-locals.el file. The cider-clojure-cli-global-options variable is depreated and it should be cider-clojure-cli-aliases Using the older variable may be breaking the cider-jack-in command. I will push an update to the repository to fix the .dir-locals.el

For reference, there is more information about configuration Cider for a project here: https://practical.li/spacemacs/clojure-development/project-configuration/

EDIT: not needed, I've reproduced the issue Can you share the command that the Cider is using when calling cider-jack-in. The command will be in the *messages* buffer (`SPC b m` in Spacemacs)

Or use SPC u before the cider jack-in command to see the full command line before executing it (it can also be edited)

I can confirm that its the old cider variable name in the .dir-locals.el file that is causing the issue. I have pushed a couple of commits that update the cider variable and the alias name. Or you could delete the .dir-locals.el file as it is not needed for this specific project The :env/testalias included in .dir-locals.el is from the https://practical.li/clojure/clojure-cli/practicalli-config/, so if that is not installed then there will be a warning about the alias not found, although this warning can be ignored as I didnt write any unit tests in the 4clojure project. Te :env/test alias adds test directory as an :extra-paths so cider test runner can find code under the test directory (but in this case no such code exists)

For simple and very standard projects, then cider-jack-in is a convenient way to start a REPL process from Emacs I often use a https://practical.li/clojure/clojure-cli/repl-reloaded/ with commercial projects so start the REPL process from the command line and include a number of supporting tools. This also means the REPL keeps running if I shut down the editor (or I want to use a different editor) This approach is something that is not required when first learning with Clojure though

I've added notes to the issue discussions included in the question to inform that cider-clojure-cli-aliases variable is the correct way to add aliases to cider-jack-in. If you have any more issues or questions about Practicalli content and examples, dont hesitate to ask (there are no silly questions)

I found a few other projects with the older variable, so your inquiry has helped me fix those too. Thank you.

I, John, your fix worked perfectly. Many thanks 🙂