How to Fix "Missing Project Reference" Errors When Compiling a CounterStrikeSharp Plugin

Spot the real error

Scroll to the top of the failed build log, above the wall of CS0246 errors. Look for a line like this one, it's the actual cause, everything below it is a consequence:

warning MSB9008: The referenced project ../ggmcAPI/ggmcAPI.csproj does not exist.

Understand what it means

The plugin's .csproj file references another project by a relative path, in the example above, a folder called ggmcAPI, sitting one level above the plugin's own folder. That folder simply isn't in your uploaded archive.

Check if it's a git submodule

Open the plugin's page on GitHub and look for a folder shown with a small arrow icon and a short commit hash instead of a normal file listing, that's a submodule. GitHub's "Download ZIP" button never includes submodule content, only a pointer to which commit it should be. You'll need to open that submodule's own repository separately and download it on its own.

Get the folder depth right

This is the step people usually get wrong on the first try. The relative path in the .csproj (../ggmcAPI in our example) is resolved against the folder containing the .csproj file itself, not against the root of your .zip archive. If your plugin folder and the dependency folder aren't siblings, one level up resolves to the wrong place.

A common mistake to avoid

Placing the dependency folder inside the plugin's own folder looks reasonable, but it isn't what the relative path expects. This structure will fail the exact same way as having no folder at all:

Recompile

Once both folders sit side by side at the correct depth, re-zip the archive and upload it again. If MSB9008 is gone from the log but you still see errors, those are now real compile errors worth looking into on their own.