diff --git a/crates/oa-desktop/src/app/source_symbols.rs b/crates/oa-desktop/src/app/source_symbols.rs
index c6fef7cc..e9a7ecae 100644
--- a/crates/oa-desktop/src/app/source_symbols.rs
+++ b/crates/oa-desktop/src/app/source_symbols.rs
@@ -529,3 +529,6 @@ impl App {
 
 #[cfg(test)]
 mod tests;
+
+#[cfg(all(test, debug_assertions))]
+mod focus_selection_tests;
diff --git a/crates/oa-desktop/src/app/source_symbols/focus_selection_tests.rs b/crates/oa-desktop/src/app/source_symbols/focus_selection_tests.rs
new file mode 100644
index 00000000..90a9d8db
--- /dev/null
+++ b/crates/oa-desktop/src/app/source_symbols/focus_selection_tests.rs
@@ -0,0 +1,481 @@
+//! The mounted CPU renderer and App use the same cosmic-text editor engine, but
+//! Iced's Content is parameterized by renderer and cannot be shared between them.
+//! We hit-test the initial click in the laid-out CPU widget, seed that raw caret
+//! in App, and relay the real subsequent SelectWord/SelectLine and editing actions.
+//! App's own Content is never replaced or cursor-normalized after selection. This
+//! tests the actual controller/content boundary without a window or GPU; native
+//! replay remains the check of the complete production renderer/layout path.
+use crate::app::Page;
+use crate::app::{App, Message};
+use crate::document::Document;
+use crate::source_navigation as nav;
+use crate::source_workspace::{LIMITS, Workspace};
+use crate::views::source_tests::FontLayout;
+use iced::advanced::{Layout, Shell, layout, widget as core_widget};
+use iced::futures::StreamExt;
+use iced::keyboard::{self, Key, Modifiers};
+use iced::widget::{button, container, row, text_editor, text_input};
+use iced::{Element, Event, Font, Size, mouse};
+use iced::{Point, Task, widget};
+use oa_core::{Project, source_project::SourceBundle};
+use std::{collections::BTreeMap, sync::Arc, sync::atomic::Ordering};
+
+const SOURCE: &str = concat!(
+    "// oa_contact tail\r\n",
+    "arcadia 7;\r\n",
+    "project model \"Selection\" id \"9e8f0000-0000-4000-8000-000000000091\" {}\r\n",
+);
+const HOST: Size = Size::new(620., 260.);
+
+fn fixture() -> App {
+    let bundle = SourceBundle {
+        entry: "project.arcadia".into(),
+        files: BTreeMap::from([("project.arcadia".into(), SOURCE.into())]),
+    };
+    let mut app = App::with_project(Project::empty());
+    app.document = Document::from_bundle(bundle, LIMITS).unwrap();
+    app.source_workspace = Workspace::new(app.document.bundle(), true);
+    app.selected = app.project().id;
+    app.refresh_draft();
+    app.page = Page::Text;
+    app.show_source_file(false);
+    app
+}
+
+fn ui<'a>(
+    app: &App,
+    content: &'a text_editor::Content<FontLayout>,
+) -> Element<'a, Message, iced::Theme, FontLayout> {
+    let find: Element<'a, Message, iced::Theme, FontLayout> = if app.source_navigation.open {
+        row![
+            text_input("Find", "")
+                .id("source-find")
+                .on_input(|s| Message::SourceNavigation(nav::Event::Query(s))),
+            container(button("Close").on_press(app.source_find_close_message()))
+                .id("selection-find-close"),
+        ]
+        .into()
+    } else {
+        widget::Space::new().into()
+    };
+    // Column::push drops zero-height children. Keep both paths mounted even
+    // while Find is hidden, as the production retained-slot layout does.
+    widget::Column::from_vec(vec![
+        container(find)
+            .height(if app.source_navigation.open { 32. } else { 0. })
+            .into(),
+        widget::text_editor(content)
+            .id(app.source_editor_id())
+            .font(Font::MONOSPACE)
+            .size(14)
+            .padding(16)
+            .height(iced::Fill)
+            .on_action(Message::SourceEdit)
+            .into(),
+    ])
+    .width(iced::Fill)
+    .height(iced::Fill)
+    .into()
+}
+
+struct Mounted {
+    content: text_editor::Content<FontLayout>,
+    tree: core_widget::Tree,
+}
+
+// Operations follow widget-provided traversal instead of assuming a fixed
+// relationship between layout nodes, transparent containers and state trees.
+struct Inspection {
+    editor: core_widget::Id,
+    focused: Option<bool>,
+    close_bounds: Option<iced::Rectangle>,
+}
+
+impl core_widget::Operation for Inspection {
+    fn traverse(&mut self, operate: &mut dyn FnMut(&mut dyn core_widget::Operation)) {
+        operate(self);
+    }
+
+    fn focusable(
+        &mut self,
+        id: Option<&core_widget::Id>,
+        _: iced::Rectangle,
+        state: &mut dyn core_widget::operation::Focusable,
+    ) {
+        if id == Some(&self.editor) {
+            assert!(
+                self.focused.replace(state.is_focused()).is_none(),
+                "duplicate editor ID"
+            );
+        }
+    }
+
+    fn container(&mut self, id: Option<&core_widget::Id>, bounds: iced::Rectangle) {
+        if id == Some(&core_widget::Id::new("selection-find-close")) {
+            assert!(
+                self.close_bounds.replace(bounds).is_none(),
+                "duplicate Close target ID"
+            );
+        }
+    }
+}
+
+impl Mounted {
+    fn new() -> Self {
+        Self {
+            content: text_editor::Content::with_text(SOURCE),
+            tree: core_widget::Tree::empty(),
+        }
+    }
+
+    fn events(&mut self, app: &App, events: &[(Event, mouse::Cursor)]) -> Vec<Message> {
+        let mut view = ui(app, &self.content);
+        self.tree.diff(view.as_widget());
+        let node = view.as_widget_mut().layout(
+            &mut self.tree,
+            &FontLayout,
+            &layout::Limits::new(Size::ZERO, HOST),
+        );
+        let mut messages = Vec::new();
+        for (event, cursor) in events {
+            let mut shell = Shell::new(&mut messages);
+            view.as_widget_mut().update(
+                &mut self.tree,
+                event,
+                Layout::new(&node),
+                *cursor,
+                &FontLayout,
+                &mut iced::advanced::clipboard::Null,
+                &mut shell,
+                &iced::Rectangle::with_size(HOST),
+            );
+            if !matches!(event, Event::Mouse(mouse::Event::ButtonReleased(_))) {
+                assert!(
+                    shell.is_event_captured(),
+                    "mounted input must be handled: {event:?}"
+                );
+            }
+        }
+        messages
+    }
+
+    fn operation(&mut self, app: &App, mut op: Box<dyn core_widget::Operation>) {
+        let mut view = ui(app, &self.content);
+        self.tree.diff(view.as_widget());
+        let node = view.as_widget_mut().layout(
+            &mut self.tree,
+            &FontLayout,
+            &layout::Limits::new(Size::ZERO, HOST),
+        );
+        loop {
+            view.as_widget_mut().operate(
+                &mut self.tree,
+                Layout::new(&node),
+                &FontLayout,
+                op.as_mut(),
+            );
+            match op.finish() {
+                core_widget::operation::Outcome::Chain(next) => op = next,
+                core_widget::operation::Outcome::None => break,
+                core_widget::operation::Outcome::Some(()) => panic!("focus does not emit messages"),
+            }
+        }
+    }
+
+    async fn task(&mut self, app: &App, task: Task<Message>) {
+        if let Some(mut actions) = iced_runtime::task::into_stream(task) {
+            while let Some(action) = actions.next().await {
+                let iced_runtime::Action::Widget(op) = action else {
+                    panic!("expected a widget operation")
+                };
+                self.operation(app, op);
+            }
+        }
+    }
+
+    fn inspect(&mut self, app: &App) -> Inspection {
+        let mut inspection = Inspection {
+            editor: app.source_editor_id(),
+            focused: None,
+            close_bounds: None,
+        };
+        let mut view = ui(app, &self.content);
+        self.tree.diff(view.as_widget());
+        let node = view.as_widget_mut().layout(
+            &mut self.tree,
+            &FontLayout,
+            &layout::Limits::new(Size::ZERO, HOST),
+        );
+        view.as_widget_mut().operate(
+            &mut self.tree,
+            Layout::new(&node),
+            &FontLayout,
+            &mut inspection,
+        );
+        inspection
+    }
+
+    fn editor_focused(&mut self, app: &App) -> bool {
+        self.inspect(app)
+            .focused
+            .expect("exactly one editor with the requested ID")
+    }
+
+    fn close_message(&mut self, app: &App, escape: bool) -> Message {
+        if escape {
+            let event = Event::Keyboard(keyboard::Event::KeyPressed {
+                key: Key::Named(keyboard::key::Named::Escape),
+                modified_key: Key::Named(keyboard::key::Named::Escape),
+                physical_key: keyboard::key::Physical::Code(keyboard::key::Code::Escape),
+                location: keyboard::Location::Standard,
+                modifiers: Modifiers::empty(),
+                text: None,
+                repeat: false,
+            });
+            assert!(
+                self.events(app, &[(event, mouse::Cursor::Unavailable)])
+                    .is_empty()
+            );
+            // The existing subscription tests cover the captured-Escape bridge.
+            // Deliver its App message after this actual input captured the key.
+            Message::Escape
+        } else {
+            let center = self
+                .inspect(app)
+                .close_bounds
+                .expect("the mounted Find Close target exists")
+                .center();
+            let cursor = mouse::Cursor::Available(center);
+            let mut messages = self.events(
+                app,
+                &[
+                    (
+                        Event::Mouse(mouse::Event::ButtonPressed(mouse::Button::Left)),
+                        cursor,
+                    ),
+                    (
+                        Event::Mouse(mouse::Event::ButtonReleased(mouse::Button::Left)),
+                        cursor,
+                    ),
+                ],
+            );
+            assert_eq!(messages.len(), 1);
+            let close = messages.remove(0);
+            assert!(matches!(close, Message::SourceFindClose(..)));
+            close
+        }
+    }
+
+    fn select(&mut self, app: &mut App, line: bool) {
+        // One mounted update batch avoids delays between Iced's consecutive-click
+        // timestamps; content actions are applied in their emitted order below.
+        let at = mouse::Cursor::Available(Point::new(65., 25.));
+        let events = (0..if line { 3 } else { 2 })
+            .flat_map(|_| {
+                [
+                    (
+                        Event::Mouse(mouse::Event::ButtonPressed(mouse::Button::Left)),
+                        at,
+                    ),
+                    (
+                        Event::Mouse(mouse::Event::ButtonReleased(mouse::Button::Left)),
+                        at,
+                    ),
+                ]
+            })
+            .collect::<Vec<_>>();
+        let messages = self.events(app, &events);
+        assert_eq!(messages.len(), if line { 3 } else { 2 });
+        for (index, message) in messages.into_iter().enumerate() {
+            let Message::SourceEdit(action) = message else {
+                panic!("editor action")
+            };
+            if index == 0 {
+                assert!(matches!(action, text_editor::Action::Click(_)));
+                self.content.perform(action);
+                let caret = self.content.cursor();
+                assert_eq!(caret.position.line, 0);
+                assert!(
+                    (4..13).contains(&caret.position.column),
+                    "click must hit inside oa_contact: {caret:?}"
+                );
+                // App's GPU-typed Content has no public layout API. Copy only the
+                // initial hit-tested caret before any Word/Line selection exists.
+                app.source_editor.move_to(caret);
+            } else {
+                assert_eq!(
+                    action,
+                    if index == 1 {
+                        text_editor::Action::SelectWord
+                    } else {
+                        text_editor::Action::SelectLine
+                    }
+                );
+                self.content.perform(action.clone());
+                let _ = app.update(Message::SourceEdit(action));
+            }
+        }
+        assert_eq!(
+            self.content.selection().as_deref(),
+            Some(if line {
+                "// oa_contact tail"
+            } else {
+                "oa_contact"
+            })
+        );
+        assert_eq!(app.source_editor.selection(), self.content.selection());
+        assert!(self.editor_focused(app));
+    }
+
+    fn type_replacement(&mut self, app: &mut App) {
+        let event = Event::Keyboard(keyboard::Event::KeyPressed {
+            key: Key::Character("x".into()),
+            modified_key: Key::Character("x".into()),
+            physical_key: keyboard::key::Physical::Code(keyboard::key::Code::KeyX),
+            location: keyboard::Location::Standard,
+            modifiers: Modifiers::empty(),
+            text: Some("x".into()),
+            repeat: false,
+        });
+        let messages = self.events(app, &[(event, mouse::Cursor::Unavailable)]);
+        assert_eq!(messages.len(), 1);
+        let Message::SourceEdit(action) = messages.into_iter().next().unwrap() else {
+            panic!("typed edit")
+        };
+        assert_eq!(
+            action,
+            text_editor::Action::Edit(text_editor::Edit::Insert('x'))
+        );
+        self.content.perform(action.clone());
+        let _ = app.update(Message::SourceEdit(action));
+    }
+}
+
+#[tokio::test]
+async fn word_and_line_selection_survive_find_close_and_escape_then_replace_exact_bytes() {
+    for line in [false, true] {
+        for escape in [false, true] {
+            let mut app = fixture();
+            let accepted = app.document.snapshot();
+            let mut mounted = Mounted::new();
+            mounted.select(&mut app, line);
+            let selected = app.source_editor.selection();
+            let cursor = app.source_editor.cursor();
+            // Word/Line selection has coincident raw endpoints. Merely checking
+            // cursor equality after a move_to roundtrip cannot detect the defect.
+            assert_eq!(cursor.selection, Some(cursor.position));
+            let task = app.update(Message::SourceNavigation(nav::Event::Open(false)));
+            mounted.task(&app, task).await;
+            assert!(!mounted.editor_focused(&app));
+            assert_eq!(app.source_editor.selection(), selected);
+            let close = mounted.close_message(&app, escape);
+            let _ = app.update(close);
+            let ticket = app
+                .source_reveal_ticket()
+                .expect("guarded restoration ticket");
+            let task = app.update(Message::SourceViewport(Some(ticket)));
+            mounted.task(&app, task).await;
+            assert!(mounted.editor_focused(&app));
+            assert_eq!(app.source_editor.cursor(), cursor);
+            assert_eq!(
+                app.source_editor.selection(),
+                selected,
+                "selected bytes must survive focus restoration"
+            );
+            assert_eq!(app.source_editor.text(), SOURCE);
+            mounted.type_replacement(&mut app);
+            let expected = SOURCE.replacen(selected.as_deref().unwrap(), "x", 1);
+            assert_eq!(app.source_editor.text(), expected);
+            assert_eq!(app.source_workspace.text(), expected);
+            assert_eq!(mounted.content.text(), expected);
+            assert!(Arc::ptr_eq(&accepted, &app.document.snapshot()));
+            assert!(!app.document.can_undo() && !app.document.can_redo());
+        }
+    }
+}
+
+#[test]
+fn mounted_direct_typing_control_and_old_cursor_roundtrip_discriminate_selection_loss() {
+    for line in [false, true] {
+        for old_roundtrip in [false, true] {
+            let mut app = fixture();
+            let mut mounted = Mounted::new();
+            mounted.select(&mut app, line);
+            let selected = app.source_editor.selection().unwrap();
+            let interior = app.source_editor.cursor();
+            if old_roundtrip {
+                app.source_editor.move_to(interior);
+                assert_ne!(
+                    app.source_editor.selection().as_deref(),
+                    Some(selected.as_str())
+                );
+            }
+            mounted.type_replacement(&mut app);
+            let expected = if old_roundtrip {
+                let mut text = SOURCE.to_owned();
+                text.insert(interior.position.column, 'x');
+                text
+            } else {
+                SOURCE.replacen(&selected, "x", 1)
+            };
+            assert_eq!(app.source_editor.text(), expected);
+            assert_eq!(app.source_workspace.text(), expected);
+            assert_eq!(mounted.content.text(), SOURCE.replacen(&selected, "x", 1));
+        }
+    }
+}
+
+#[tokio::test]
+async fn stale_focus_ticket_and_later_raw_input_cannot_steal_focus_or_change_selected_bytes() {
+    for later_raw_input in [false, true] {
+        let mut app = fixture();
+        let mut mounted = Mounted::new();
+        mounted.select(&mut app, false);
+        let selected = app.source_editor.selection();
+        let open = app.update(Message::SourceNavigation(nav::Event::Open(false)));
+        mounted.task(&app, open).await;
+        let close = app.source_find_close_message();
+        let _ = app.update(close);
+        let ticket = app.source_reveal_ticket().unwrap();
+        let focus = if later_raw_input {
+            app.update(Message::SourceViewport(Some(ticket)))
+        } else {
+            Task::none()
+        };
+        let reopen = app.update(Message::SourceNavigation(nav::Event::Open(false)));
+        mounted.task(&app, reopen).await;
+        if later_raw_input {
+            app.source_symbols
+                .raw_interaction
+                .fetch_add(1, Ordering::SeqCst);
+            mounted.task(&app, focus).await;
+        } else {
+            let stale = app.update(Message::SourceViewport(Some(ticket)));
+            mounted.task(&app, stale).await;
+        }
+        assert!(app.source_navigation.open);
+        assert!(!mounted.editor_focused(&app));
+        assert_eq!(app.source_editor.selection(), selected);
+        assert_eq!(app.source_editor.text(), SOURCE);
+    }
+}
+
+#[tokio::test]
+async fn explicit_cursor_navigation_still_moves_and_selects_requested_line() {
+    let mut app = fixture();
+    let mut mounted = Mounted::new();
+    mounted.select(&mut app, false);
+    let target = text_editor::Cursor {
+        position: text_editor::Position { line: 1, column: 3 },
+        selection: None,
+    };
+    // Clear the previous semantic selection as actual show_source_file does when
+    // moving to another source buffer, then exercise intentional navigation.
+    app.show_source_file(false);
+    app.queue_source_reveal(target, true);
+    let ticket = app.source_reveal_ticket().unwrap();
+    let task = app.update(Message::SourceViewport(Some(ticket)));
+    mounted.task(&app, task).await;
+    assert_eq!(app.source_editor.cursor().position, target.position);
+    assert_eq!(app.source_editor.selection().as_deref(), Some("arcadia 7;"));
+}