feat(desktop): promote workspace sessions in place

Author: 1jehuang

crates/jcode-desktop/src/main.rs

@@ -835,7 +835,12 @@ async fn run() -> Result<()> {
                             if let DesktopApp::Workspace(workspace) = &app {
                                 queue_desktop_preferences_save(workspace, &preferences_save_tx);
                             }
-                            if let Err(error) =
+                            if app.promote_focused_workspace_session() {
+                                scroll_accumulator = ScrollLineAccumulator::default();
+                                scroll_metrics_cache = SingleSessionScrollMetricsCache::default();
+                                window.set_title(&app.status_title());
+                                window.request_redraw();
+                            } else if let Err(error) =
                                 session_launch::launch_validated_resume_session(&session_id, &title)
                             {
                                 desktop_log::error(format_args!(
@@ -4829,6 +4834,21 @@ impl DesktopApp {
         }
     }
 
+    fn promote_focused_workspace_session(&mut self) -> bool {
+        let Self::Workspace(workspace) = self else {
+            return false;
+        };
+        let Some(card) = workspace.focused_session_card() else {
+            return false;
+        };
+        let session_id = card.session_id.clone();
+        let mut single_session = SingleSessionApp::new(Some(card));
+        single_session.initialize_resumed_session(&session_id);
+        single_session.hydrate_resumed_session_from_disk(&session_id);
+        *self = Self::SingleSession(single_session);
+        true
+    }
+
     fn apply_session_event(&mut self, event: session_launch::DesktopSessionEvent) {
         if let Self::SingleSession(app) = self {
             app.apply_session_event(event);

crates/jcode-desktop/src/main_tests.rs

@@ -6465,6 +6465,24 @@ fn single_session_wraps_one_session_card() {
     );
 }
 
+#[test]
+fn workspace_focused_session_promotes_to_single_session_app() {
+    let mut app = DesktopApp::Workspace(Workspace::from_session_cards(vec![workspace::SessionCard {
+        session_id: "session_alpha".to_string(),
+        title: "alpha".to_string(),
+        subtitle: "active".to_string(),
+        detail: "3 msgs".to_string(),
+        preview_lines: vec!["user hello".to_string()],
+        detail_lines: vec!["assistant hi".to_string()],
+    }]));
+
+    assert!(app.promote_focused_workspace_session());
+    let snapshot = app.debug_snapshot();
+    assert_eq!(snapshot.mode, "single_session");
+    assert_eq!(snapshot.live_session_id.as_deref(), Some("session_alpha"));
+    assert!(snapshot.body_text.contains("user hello"));
+}
+
 #[test]
 fn single_session_surface_is_the_panel_primitive() {
     let card = workspace::SessionCard {

crates/jcode-desktop/src/workspace.rs

@@ -613,6 +613,26 @@ impl Workspace {
         })
     }
 
+    pub fn focused_session_card(&self) -> Option<SessionCard> {
+        self.focused_surface().and_then(|surface| {
+            let session_id = surface.session_id.as_ref()?.clone();
+            Some(SessionCard {
+                session_id,
+                title: surface.title.clone(),
+                subtitle: surface.body_lines.first().cloned().unwrap_or_default(),
+                detail: surface.body_lines.get(1).cloned().unwrap_or_default(),
+                preview_lines: surface
+                    .body_lines
+                    .iter()
+                    .skip_while(|line| line.as_str() != "recent transcript")
+                    .skip(1)
+                    .cloned()
+                    .collect(),
+                detail_lines: surface.detail_lines.clone(),
+            })
+        })
+    }
+
     pub fn is_focused(&self, surface_id: u64) -> bool {
         self.focused_id == surface_id
     }