feat: experimental menu (#8071)

This will automatically render any `Stage::Beta` features.

The change only gets applied to the *next session*. This started as a
bug but actually this is a good thing to prevent out of distribution
push

<img width="986" height="288" alt="Screenshot 2025-12-15 at 15 38 35"
src="https://github.com/user-attachments/assets/78b7a71d-0e43-4828-a118-91c5237909c7"
/>


<img width="509" height="109" alt="Screenshot 2025-12-15 at 17 35 44"
src="https://github.com/user-attachments/assets/6933de52-9b66-4abf-b58b-a5f26d5747e2"
/>

codex-rs/tui/src/bottom_pane/experimental_features_view.rs

@@ -0,0 +1,292 @@
+use crossterm::event::KeyCode;
+use crossterm::event::KeyEvent;
+use crossterm::event::KeyModifiers;
+use ratatui::buffer::Buffer;
+use ratatui::layout::Constraint;
+use ratatui::layout::Layout;
+use ratatui::layout::Rect;
+use ratatui::style::Stylize;
+use ratatui::text::Line;
+use ratatui::widgets::Block;
+use ratatui::widgets::Widget;
+
+use crate::app_event::AppEvent;
+use crate::app_event_sender::AppEventSender;
+use crate::key_hint;
+use crate::render::Insets;
+use crate::render::RectExt as _;
+use crate::render::renderable::ColumnRenderable;
+use crate::render::renderable::Renderable;
+use crate::style::user_message_style;
+
+use codex_core::features::Feature;
+
+use super::CancellationEvent;
+use super::bottom_pane_view::BottomPaneView;
+use super::popup_consts::MAX_POPUP_ROWS;
+use super::scroll_state::ScrollState;
+use super::selection_popup_common::GenericDisplayRow;
+use super::selection_popup_common::measure_rows_height;
+use super::selection_popup_common::render_rows;
+
+pub(crate) struct BetaFeatureItem {
+    pub feature: Feature,
+    pub name: String,
+    pub description: String,
+    pub enabled: bool,
+}
+
+pub(crate) struct ExperimentalFeaturesView {
+    features: Vec<BetaFeatureItem>,
+    state: ScrollState,
+    complete: bool,
+    app_event_tx: AppEventSender,
+    header: Box<dyn Renderable>,
+    footer_hint: Line<'static>,
+}
+
+impl ExperimentalFeaturesView {
+    pub(crate) fn new(features: Vec<BetaFeatureItem>, app_event_tx: AppEventSender) -> Self {
+        let mut header = ColumnRenderable::new();
+        header.push(Line::from("Experimental features".bold()));
+        header.push(Line::from(
+            "Toggle beta features. Changes are saved to config.toml.".dim(),
+        ));
+
+        let mut view = Self {
+            features,
+            state: ScrollState::new(),
+            complete: false,
+            app_event_tx,
+            header: Box::new(header),
+            footer_hint: experimental_popup_hint_line(),
+        };
+        view.initialize_selection();
+        view
+    }
+
+    fn initialize_selection(&mut self) {
+        if self.visible_len() == 0 {
+            self.state.selected_idx = None;
+        } else if self.state.selected_idx.is_none() {
+            self.state.selected_idx = Some(0);
+        }
+    }
+
+    fn visible_len(&self) -> usize {
+        self.features.len()
+    }
+
+    fn build_rows(&self) -> Vec<GenericDisplayRow> {
+        let mut rows = Vec::with_capacity(self.features.len());
+        let selected_idx = self.state.selected_idx;
+        for (idx, item) in self.features.iter().enumerate() {
+            let prefix = if selected_idx == Some(idx) {
+                '›'
+            } else {
+                ' '
+            };
+            let marker = if item.enabled { 'x' } else { ' ' };
+            let name = format!("{prefix} [{marker}] {}", item.name);
+            rows.push(GenericDisplayRow {
+                name,
+                description: Some(item.description.clone()),
+                ..Default::default()
+            });
+        }
+
+        rows
+    }
+
+    fn move_up(&mut self) {
+        let len = self.visible_len();
+        if len == 0 {
+            return;
+        }
+        self.state.move_up_wrap(len);
+        self.state.ensure_visible(len, MAX_POPUP_ROWS.min(len));
+    }
+
+    fn move_down(&mut self) {
+        let len = self.visible_len();
+        if len == 0 {
+            return;
+        }
+        self.state.move_down_wrap(len);
+        self.state.ensure_visible(len, MAX_POPUP_ROWS.min(len));
+    }
+
+    fn toggle_selected(&mut self) {
+        let Some(selected_idx) = self.state.selected_idx else {
+            return;
+        };
+
+        if let Some(item) = self.features.get_mut(selected_idx) {
+            item.enabled = !item.enabled;
+        }
+    }
+
+    fn rows_width(total_width: u16) -> u16 {
+        total_width.saturating_sub(2)
+    }
+}
+
+impl BottomPaneView for ExperimentalFeaturesView {
+    fn handle_key_event(&mut self, key_event: KeyEvent) {
+        match key_event {
+            KeyEvent {
+                code: KeyCode::Up, ..
+            }
+            | KeyEvent {
+                code: KeyCode::Char('p'),
+                modifiers: KeyModifiers::CONTROL,
+                ..
+            }
+            | KeyEvent {
+                code: KeyCode::Char('\u{0010}'),
+                modifiers: KeyModifiers::NONE,
+                ..
+            } => self.move_up(),
+            KeyEvent {
+                code: KeyCode::Char('k'),
+                modifiers: KeyModifiers::NONE,
+                ..
+            } => self.move_up(),
+            KeyEvent {
+                code: KeyCode::Down,
+                ..
+            }
+            | KeyEvent {
+                code: KeyCode::Char('n'),
+                modifiers: KeyModifiers::CONTROL,
+                ..
+            }
+            | KeyEvent {
+                code: KeyCode::Char('\u{000e}'),
+                modifiers: KeyModifiers::NONE,
+                ..
+            } => self.move_down(),
+            KeyEvent {
+                code: KeyCode::Char('j'),
+                modifiers: KeyModifiers::NONE,
+                ..
+            } => self.move_down(),
+            KeyEvent {
+                code: KeyCode::Enter,
+                modifiers: KeyModifiers::NONE,
+                ..
+            } => self.toggle_selected(),
+            KeyEvent {
+                code: KeyCode::Esc, ..
+            } => {
+                self.on_ctrl_c();
+            }
+            _ => {}
+        }
+    }
+
+    fn is_complete(&self) -> bool {
+        self.complete
+    }
+
+    fn on_ctrl_c(&mut self) -> CancellationEvent {
+        // Save the updates
+        if !self.features.is_empty() {
+            let updates = self
+                .features
+                .iter()
+                .map(|item| (item.feature, item.enabled))
+                .collect();
+            self.app_event_tx
+                .send(AppEvent::UpdateFeatureFlags { updates });
+        }
+
+        self.complete = true;
+        CancellationEvent::Handled
+    }
+}
+
+impl Renderable for ExperimentalFeaturesView {
+    fn render(&self, area: Rect, buf: &mut Buffer) {
+        if area.height == 0 || area.width == 0 {
+            return;
+        }
+
+        let [content_area, footer_area] =
+            Layout::vertical([Constraint::Fill(1), Constraint::Length(1)]).areas(area);
+
+        Block::default()
+            .style(user_message_style())
+            .render(content_area, buf);
+
+        let header_height = self
+            .header
+            .desired_height(content_area.width.saturating_sub(4));
+        let rows = self.build_rows();
+        let rows_width = Self::rows_width(content_area.width);
+        let rows_height = measure_rows_height(
+            &rows,
+            &self.state,
+            MAX_POPUP_ROWS,
+            rows_width.saturating_add(1),
+        );
+        let [header_area, _, list_area] = Layout::vertical([
+            Constraint::Max(header_height),
+            Constraint::Max(1),
+            Constraint::Length(rows_height),
+        ])
+        .areas(content_area.inset(Insets::vh(1, 2)));
+
+        self.header.render(header_area, buf);
+
+        if list_area.height > 0 {
+            let render_area = Rect {
+                x: list_area.x.saturating_sub(2),
+                y: list_area.y,
+                width: rows_width.max(1),
+                height: list_area.height,
+            };
+            render_rows(
+                render_area,
+                buf,
+                &rows,
+                &self.state,
+                MAX_POPUP_ROWS,
+                "No experimental features available for now",
+            );
+        }
+
+        let hint_area = Rect {
+            x: footer_area.x + 2,
+            y: footer_area.y,
+            width: footer_area.width.saturating_sub(2),
+            height: footer_area.height,
+        };
+        self.footer_hint.clone().dim().render(hint_area, buf);
+    }
+
+    fn desired_height(&self, width: u16) -> u16 {
+        let rows = self.build_rows();
+        let rows_width = Self::rows_width(width);
+        let rows_height = measure_rows_height(
+            &rows,
+            &self.state,
+            MAX_POPUP_ROWS,
+            rows_width.saturating_add(1),
+        );
+
+        let mut height = self.header.desired_height(width.saturating_sub(4));
+        height = height.saturating_add(rows_height + 3);
+        height.saturating_add(1)
+    }
+}
+
+fn experimental_popup_hint_line() -> Line<'static> {
+    Line::from(vec![
+        "Press ".into(),
+        key_hint::plain(KeyCode::Enter).into(),
+        " to toggle or ".into(),
+        key_hint::plain(KeyCode::Esc).into(),
+        " to save for next conversation".into(),
+    ])
+}

codex-rs/tui/src/bottom_pane/mod.rs

@@ -25,6 +25,7 @@ mod chat_composer;
 mod chat_composer_history;
 mod command_popup;
 pub mod custom_prompt_view;
+mod experimental_features_view;
 mod file_search_popup;
 mod footer;
 mod list_selection_view;
@@ -53,6 +54,8 @@ pub(crate) use chat_composer::InputResult;
 use codex_protocol::custom_prompts::CustomPrompt;
 
 use crate::status_indicator_widget::StatusIndicatorWidget;
+pub(crate) use experimental_features_view::BetaFeatureItem;
+pub(crate) use experimental_features_view::ExperimentalFeaturesView;
 pub(crate) use list_selection_view::SelectionAction;
 pub(crate) use list_selection_view::SelectionItem;
 

codex-rs/tui/src/bottom_pane/selection_popup_common.rs

@@ -15,6 +15,7 @@ use crate::key_hint::KeyBinding;
 use super::scroll_state::ScrollState;
 
 /// A generic representation of a display row for selection popups.
+#[derive(Default)]
 pub(crate) struct GenericDisplayRow {
     pub name: String,
     pub display_shortcut: Option<KeyBinding>,