chore(config) personality as a feature (#10116)

## Summary
Sets up an explicit Feature flag for `/personality`, so users can now
opt in to it via `/experimental`. #10114 also updates the config

## Testing
- [x] Tested locally

codex-rs/tui/src/chatwidget.rs

@@ -2892,6 +2892,7 @@ impl ChatWidget {
         let personality = self
             .config
             .model_personality
+            .filter(|_| self.config.features.enabled(Feature::Personality))
             .filter(|_| self.current_model_supports_personality());
         let op = Op::UserTurn {
             items,
@@ -3455,19 +3456,23 @@ impl ChatWidget {
             );
             return;
         }
+        if !self.current_model_supports_personality() {
+            let current_model = self.current_model();
+            self.add_error_message(format!(
+                "Current model ({current_model}) doesn't support personalities. Try /model to pick a different model."
+            ));
+            return;
+        }
         self.open_personality_popup_for_current_model();
     }
 
     fn open_personality_popup_for_current_model(&mut self) {
-        let current_model = self.current_model();
-        let current_personality = self.config.model_personality;
+        let current_personality = self
+            .config
+            .model_personality
+            .unwrap_or(Personality::Friendly);
         let personalities = [Personality::Friendly, Personality::Pragmatic];
         let supports_personality = self.current_model_supports_personality();
-        let disabled_message = (!supports_personality).then(|| {
-            format!(
-                "Current model ({current_model}) doesn't support personalities. Try /model to switch to a newer model."
-            )
-        });
 
         let items: Vec<SelectionItem> = personalities
             .into_iter()
@@ -3492,7 +3497,7 @@ impl ChatWidget {
                 SelectionItem {
                     name,
                     description,
-                    is_current: current_personality == Some(personality),
+                    is_current: current_personality == personality,
                     is_disabled: !supports_personality,
                     actions,
                     dismiss_on_select: true,
@@ -3504,11 +3509,8 @@ impl ChatWidget {
         let mut header = ColumnRenderable::new();
         header.push(Line::from("Select Personality".bold()));
         header.push(Line::from(
-            "Choose a communication style for future responses.".dim(),
+            "Choose a communication style for Codex. Disable in /experimental.".dim(),
         ));
-        if let Some(message) = disabled_message {
-            header.push(Line::from(message.red()));
-        }
 
         self.bottom_pane.show_selection_view(SelectionViewParams {
             header: Box::new(header),
@@ -4714,6 +4716,9 @@ impl ChatWidget {
             self.refresh_model_display();
             self.request_redraw();
         }
+        if feature == Feature::Personality {
+            self.sync_personality_command_enabled();
+        }
         #[cfg(target_os = "windows")]
         if matches!(
             feature,
@@ -4780,7 +4785,6 @@ impl ChatWidget {
             mask.model = Some(model.to_string());
         }
         self.refresh_model_display();
-        self.sync_personality_command_enabled();
     }
 
     pub(crate) fn current_model(&self) -> &str {
@@ -4795,7 +4799,7 @@ impl ChatWidget {
 
     fn sync_personality_command_enabled(&mut self) {
         self.bottom_pane
-            .set_personality_command_enabled(self.current_model_supports_personality());
+            .set_personality_command_enabled(self.config.features.enabled(Feature::Personality));
     }
 
     fn current_model_supports_personality(&self) -> bool {

codex-rs/tui/src/chatwidget/snapshots/codex_tui__chatwidget__tests__personality_selection_popup.snap

@@ -3,9 +3,9 @@ source: tui/src/chatwidget/tests.rs
 expression: popup
 ---
   Select Personality
-  Choose a communication style for future responses.
+  Choose a communication style for Codex. Disable in /experimental.
 
-› 1. Friendly   Warm, collaborative, and helpful.
-  2. Pragmatic  Concise, task-focused, and direct.
+› 1. Friendly (current)  Warm, collaborative, and helpful.
+  2. Pragmatic           Concise, task-focused, and direct.
 
   Press enter to confirm or esc to go back

codex-rs/tui/src/chatwidget/tests.rs

@@ -2408,6 +2408,7 @@ async fn collab_mode_enabling_keeps_custom_until_selected() {
 #[tokio::test]
 async fn user_turn_includes_personality_from_config() {
     let (mut chat, _rx, mut op_rx) = make_chatwidget_manual(Some("bengalfox")).await;
+    chat.set_feature_enabled(Feature::Personality, true);
     chat.thread_id = Some(ThreadId::new());
     chat.set_model("bengalfox");
     chat.set_personality(Personality::Friendly);

codex-rs/tui/src/slash_command.rs

@@ -61,7 +61,7 @@ impl SlashCommand {
             SlashCommand::Status => "show current session configuration and token usage",
             SlashCommand::Ps => "list background terminals",
             SlashCommand::Model => "choose what model and reasoning effort to use",
-            SlashCommand::Personality => "choose a communication style for responses",
+            SlashCommand::Personality => "choose a communication style for Codex",
             SlashCommand::Collab => "change collaboration mode (experimental)",
             SlashCommand::Agent => "switch the active agent thread",
             SlashCommand::Approvals => "choose what Codex can do without approval",