NgDoc searches for the configuration file upward, folder by folder. The two engines start and stop the search in different folders: the new engine stops at the workspace root, and the legacy builders stop at your home directory.
Engine
Search starts in
File names
New engine
The parent of the default documentation folder, usually the project folder
So a file in src/ng-doc.config.ts is found only by the legacy builders. Put the file in the project folder or at the workspace root, where both engines find it.
The Vite plugin's generator.configFile, the --config flag of the ng-doc command, or the ngDoc.config option of the legacy builders can point to a specific file instead. See Builders, plugin and CLI and Legacy builders. Without a configuration file, every option keeps its default.
Defaults per engine
Setting
New engine
Legacy builders
cache
true
false
Cache folder
.cache/ng-doc/<project-name>
node_modules/.cache/ng-doc
Generated folder
ng-doc/<project-name> (.ng-doc/<project-name> for the ng-doc command)
ng-doc/<project-name>
Configuration search
Starts in the parent of the documentation folder
Starts in the folder of the browser entry file
Paths are relative to the workspace root. The ng-doc command line interface uses its own defaults for the documentation, generated and cache folders (Builders, plugin and CLI).