Function session_hosted_resource 

pub fn session_hosted_resource() -> Option<String>

The resource address the session’s document host keeps for this launch’s app, when the session launched it: what the app reads its state from and submits its actions against, over its one connection (docs/designs/app-language/one-app-model.md §4). None for a launch the session did not make, and for every app whose record it keeps here.

Read here, in the native runner, as every other host input the process carries is: the portable toolkit is handed the value, never reads it.