Wildcards that are in the middle of a permission string are not working.

Example: Giving a player nucleus.*.exempt.cost and then testing if they have the permission nucleus.rtp.exempt.cost yields an undefined result.

Running LuckPerms Sponge v3.1.26 on SpongeForge 1.11.2-2282-6.0.0-BETA-2287

You can use this as a temporary workaround : https://github.com/lucko/LuckPerms/wiki/Advanced-Setup#regex

Thanks. I know about regex (and am using it already) but I'd still expect it to work.

This is expected behaviour for wildcards. You can only use them at the end of a permission.

If you want to include them in the middle, use regex permissions.