fix(tui): restore auto model mode on session load

crates/tui/src/commands/session.rs

@@ -94,8 +94,7 @@ pub fn load(app: &mut App, path: Option<&str>) -> CommandResult {
     app.extend_history(cells_to_add);
     app.mark_history_updated();
     app.viewport.transcript_selection.clear();
-    app.model.clone_from(&session.metadata.model);
-    app.update_model_compaction_budget();
+    app.restore_model_selection(session.metadata.model.clone());
     app.workspace.clone_from(&session.metadata.workspace);
     app.session.total_tokens = u32::try_from(session.metadata.total_tokens).unwrap_or(u32::MAX);
     app.session.total_conversation_tokens = app.session.total_tokens;
@@ -448,6 +447,44 @@ mod tests {
         assert!(matches!(result.action, Some(AppAction::SyncSession { .. })));
     }
 
+    #[test]
+    fn load_auto_model_session_restores_auto_mode() {
+        let tmpdir = TempDir::new().unwrap();
+        let mut saved_app = create_test_app_with_tmpdir(&tmpdir);
+        saved_app.model = "auto".to_string();
+        saved_app.auto_model = true;
+        saved_app.reasoning_effort = crate::tui::app::ReasoningEffort::Auto;
+        saved_app.api_messages.push(crate::models::Message {
+            role: "user".to_string(),
+            content: vec![crate::models::ContentBlock::Text {
+                text: "Hello".to_string(),
+                cache_control: None,
+            }],
+        });
+        let save_path = tmpdir.path().join("auto_model.json");
+        save(&mut saved_app, Some(save_path.to_str().unwrap()));
+
+        let mut app = create_test_app_with_tmpdir(&tmpdir);
+        app.auto_model = false;
+        app.model = crate::config::DEFAULT_TEXT_MODEL.to_string();
+
+        let result = load(&mut app, Some(save_path.to_str().unwrap()));
+
+        assert!(!result.is_error);
+        assert_eq!(app.model, "auto");
+        assert!(app.auto_model);
+        assert_eq!(app.last_effective_model, None);
+        assert_eq!(app.reasoning_effort, crate::tui::app::ReasoningEffort::Auto);
+        assert_eq!(
+            app.effective_model_for_budget(),
+            crate::config::DEFAULT_TEXT_MODEL
+        );
+        match result.action {
+            Some(AppAction::SyncSession { model, .. }) => assert_eq!(model, "auto"),
+            other => panic!("expected SyncSession action, got {other:?}"),
+        }
+    }
+
     #[test]
     fn load_restores_artifact_registry() {
         let tmpdir = TempDir::new().unwrap();

crates/tui/src/tui/app.rs

@@ -3991,6 +3991,18 @@ impl App {
             compaction_threshold_for_model_and_effort(&model, self.reasoning_effort.api_value());
     }
 
+    pub fn restore_model_selection(&mut self, model: String) {
+        let auto_model = model.trim().eq_ignore_ascii_case("auto");
+        self.model = model;
+        self.auto_model = auto_model;
+        self.last_effective_model = None;
+        self.last_effective_reasoning_effort = None;
+        if auto_model {
+            self.reasoning_effort = ReasoningEffort::Auto;
+        }
+        self.update_model_compaction_budget();
+    }
+
     pub fn effective_model_for_budget(&self) -> &str {
         if self.auto_model {
             return self

crates/tui/src/tui/ui.rs

@@ -6202,8 +6202,7 @@ fn apply_loaded_session(app: &mut App, config: &Config, session: &SavedSession)
     app.sync_context_references_from_session(&session.context_references, &message_to_cell);
     app.mark_history_updated();
     app.viewport.transcript_selection.clear();
-    app.model.clone_from(&session.metadata.model);
-    app.update_model_compaction_budget();
+    app.restore_model_selection(session.metadata.model.clone());
     apply_workspace_runtime_state(app, config, session.metadata.workspace.clone());
     app.session.total_tokens = u32::try_from(session.metadata.total_tokens).unwrap_or(u32::MAX);
     app.session.total_conversation_tokens = app.session.total_tokens;

crates/tui/src/tui/ui/tests.rs

@@ -1367,6 +1367,27 @@ fn apply_loaded_session_resets_unpersisted_telemetry() {
     assert!(app.session.turn_cache_history.is_empty());
 }
 
+#[test]
+fn apply_loaded_session_restores_auto_model_mode() {
+    let mut app = create_test_app();
+    app.auto_model = false;
+    app.model = crate::config::DEFAULT_TEXT_MODEL.to_string();
+    let mut session = saved_session_with_messages(vec![text_message("assistant", "ready")]);
+    session.metadata.model = "auto".to_string();
+
+    let recovered = apply_loaded_session(&mut app, &Config::default(), &session);
+
+    assert!(!recovered);
+    assert_eq!(app.model, "auto");
+    assert!(app.auto_model);
+    assert_eq!(app.last_effective_model, None);
+    assert_eq!(app.reasoning_effort, crate::tui::app::ReasoningEffort::Auto);
+    assert_eq!(
+        app.effective_model_for_budget(),
+        crate::config::DEFAULT_TEXT_MODEL
+    );
+}
+
 #[tokio::test]
 async fn apply_loaded_session_resets_workspace_runtime_state() {
     let mut app = create_test_app();