diff --git a/docs/theme.md b/docs/theme.md
index 8290410..bf3bdeb 100644
--- a/docs/theme.md
+++ b/docs/theme.md
@@ -17,6 +17,10 @@ podcast-ui.css, feeds.js) and diora-desktop (desktop.css).
   answers that query from the app's own (dark) theme, not the system's: there the page asks
   `DioraNative.systemScheme()` ("dark" | "light") and the app calls
   `window.__dioraSystemScheme(scheme)` when the system switches (uiMode change, or on return).
+* The desktop app (Electron) sets `nativeTheme.themeSource` to the scheme for a fixed choice
+  (title bar, scrollbars, form controls match) but leaves it on `"system"` for "auto", so
+  `prefers-color-scheme` there is the system's; the page tells it the choice along with the
+  scheme (`dioraDesktop.setTheme(scheme, choice)`, desktop 0.1.31).
 * E-ink mode (`html.nui-eink`) keeps its own black-on-white rules and ignores this.
 * The reader has its own themes; its default is now "Wie die App" (`readerSettings.theme = 'app'`):
   dark → reader dark, light → reader bright. Sepia, Dunkel and Hell stay choosable.