The language server
The VS Code extension bundles a language server, aui-lsp. It speaks LSP over stdio and compiles the very same Core/ sources the Unity importer uses, which is why its diagnostics match the Unity console exactly rather than approximating it.
You do not need this page to use the extension. It matters if you want AUI's diagnostics in another editor, or in a check step.
Requirements
The .NET 8 runtime or newer, on the PATH as dotnet.
Using it from another editor
Any LSP client can drive it. Point the client at the bundled server and register the two languages:
| Language id | Extension |
|---|---|
aui | .aui |
auis | .auis |
Launch it as dotnet <path>/aui-lsp.dll, communicating over stdio. The workspace root should be the world project folder, the one containing Assets/.
The server discovers the project the same way the Unity editor does: it reads Assets/AUI/AuiSettings.asset for the language folder, the default language and the component and icon folders, and falls back to Assets/AUI/Lang or any folder called lang.
Capabilities
Diagnostics, completion, hover, go to definition, find references, rename, code actions, document links, colour provider, inlay hints, document symbols, workspace symbols, and semantic tokens.
Semantic tokens matter for embedded stylesheets: the server tokenises style="" attributes and <style> blocks with a forgiving lexer that does not depend on the client's grammar, so they colour correctly wherever you use it.
Checking a project without an editor
The extension ships a smoke script that drives the server over stdio and exercises every capability against a real view:
node smoke.js <workspaceRoot> <path/to/View.aui>It exits 1 on a failure, so it works as a check step in a build script.
For validating the actual views in a project, Unity's own AUI/Validate is the better tool: it compiles every view and prints every diagnostic, warnings included.
Why the diagnostics always agree
Core/ is a plain C# library with no Unity references at all, and both hosts compile the same files: the Unity editor assembly includes them, and the language server project includes them by path. There is no second implementation of the parser, the cascade or the layout solver to drift out of sync.
The only difference is what each host supplies: the Unity host measures text with real TMP metrics and records asset dependencies, while the server uses a heuristic measurer. So layout warnings can differ slightly in the editor; everything else is identical.
Next
- The VS Code extension for the normal way to use this.
- How it works for the pipeline both hosts run.