Allow choosing the model for draft sessions

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/app.rs

@@ -538,6 +538,7 @@ pub(crate) enum Message {
     DeleteProject(i32),
     CreateSession(i32),
     DraftProjectChanged(i32),
+    DraftModelChanged(ModelChoice),
     SwitchGitBranch(String),
     ReasoningModeChanged(ReasoningMode),
     PermissionModeChanged(PermissionMode),
@@ -1843,6 +1844,16 @@ impl App {
                 }
             }
             Message::DraftProjectChanged(project_id) => self.move_draft_to_project(project_id),
+            Message::DraftModelChanged(model) => {
+                if self.selected_session.is_some() {
+                    self.error = Some("The model is fixed once a chat has started.".into());
+                } else if self.active_chat_count() > 0 {
+                    self.error =
+                        Some("Stop all active generations before changing the model.".into());
+                } else if let Err(error) = self.activate_model(model) {
+                    self.error = Some(error);
+                }
+            }
             Message::SwitchGitBranch(branch) => self.switch_git_branch(&branch),
             Message::ReasoningModeChanged(mode) => {
                 if self.active_chat_count() > 0 {

src/app/view/chat.rs

@@ -337,6 +337,20 @@ impl App {
                 .padding([2, 6])
                 .into()
             };
+            // A draft has no user message yet, so its model is still open.
+            let model_control: Element<'_, Message> =
+                if self.selected_session.is_none() && self.active_chat_count() == 0 {
+                    pick_list(
+                        model::installed_models(&models_path()),
+                        Some(self.config.model),
+                        Message::DraftModelChanged,
+                    )
+                    .text_size(12)
+                    .padding([2, 6])
+                    .into()
+                } else {
+                    text(self.config.model.to_string()).size(12).into()
+                };
             let vision_ready = self.config.model.supports_vision()
                 && model::engine_artifacts(self.config.model, false, &models_path())
                     .vision
@@ -399,7 +413,7 @@ impl App {
                         .padding([2, 6]),
                         reasoning_control,
                         icon(ICON_MODEL, 16),
-                        text(self.config.model.to_string()).size(12),
+                        model_control,
                         action,
                     ]
                     .spacing(6)