How resources reach the clients

There are two separate downloads. Content mods are game files and go through the launcher before the game starts. Resource files are scripts and UI and go through the client mod after the player joined.

Content mods

1. You put mod_*.pak, .utoc and .ucas files into client-mods\.
2. The runner lists every file in the server entry with a download URL on sv_httpport under /mods/.
3. The launcher downloads what is missing or changed, checks it and places the files into its copy of the game before the start.
4. The game mounts them at startup.

Mods must be IoStore containers for UE 5.6 (.pak + .utoc + .ucas). A plain legacy .pak is found but never mounted.

Put the same files into server-mods\ when the server needs the content too, for example new species.

Resource files

After the join the client mod connects to your server and downloads the client files of every loaded resource. They stay in memory and are never written to the player's disk. When all files are there, the client scripts start.

Which files a client can get

Only files that the manifest declares with client, files or nui, plus manifest.lua. Server scripts and data files such as data.json are never sent to players.

Keep admin actions on the server side. See admin checks.