diff --git a/codex-rs/tui/src/bottom_pane/chat_composer.rs b/codex-rs/tui/src/bottom_pane/chat_composer.rs
index 6abe624051..8e166f8287 100644
--- a/codex-rs/tui/src/bottom_pane/chat_composer.rs
+++ b/codex-rs/tui/src/bottom_pane/chat_composer.rs
@@ -13,6 +13,8 @@ use tui_textarea::Input;
 use tui_textarea::Key;
 use tui_textarea::TextArea;
 
+use super::command_popup::CommandPopup;
+
 /// Minimum number of visible text rows inside the textarea.
 const MIN_TEXTAREA_ROWS: usize = 1;
 /// Rows consumed by the border.
@@ -24,9 +26,10 @@ pub enum InputResult {
     None,
 }
 
-pub(crate) struct ChatComposer<'a> {
-    textarea: TextArea<'a>,
-}
+    pub(crate) struct ChatComposer<'a> {
+        textarea: TextArea<'a>,
+        command_popup: Option<CommandPopup>,
+    }
 
 impl ChatComposer<'_> {
     pub fn new(has_input_focus: bool) -> Self {
@@ -34,7 +37,10 @@ impl ChatComposer<'_> {
         textarea.set_placeholder_text("send a message");
         textarea.set_cursor_line_style(ratatui::style::Style::default());
 
-        let mut this = Self { textarea };
+        let mut this = Self {
+            textarea,
+            command_popup: None,
+        };
         this.update_border(has_input_focus);
         this
     }
@@ -43,9 +49,116 @@ impl ChatComposer<'_> {
         self.update_border(has_focus);
     }
 
-    /// Handle key event when no overlay is present.
+    /// Synchronize `self.command_popup` with the current text in the
+    /// textarea. This must be called after every modification that can change
+    /// the text so the popup is shown/updated/hidden as appropriate.
+    fn sync_command_popup(&mut self) {
+        // Inspect only the first line to decide whether to show the popup. In
+        // the common case (no leading slash) we avoid copying the entire
+        // textarea contents.
+        let first_line = self
+            .textarea
+            .lines()
+            .first()
+            .map(|s| s.as_str())
+            .unwrap_or("");
+
+        if first_line.starts_with('/') {
+            // Create popup lazily when the user starts a slash command.
+            let popup = self
+                .command_popup
+                .get_or_insert_with(CommandPopup::new);
+
+            // Forward *only* the first line since `CommandPopup` only needs
+            // the command token.
+            popup.on_composer_text_change(first_line.to_string());
+        } else {
+            // Remove popup when '/' is no longer the first character.
+            self.command_popup = None;
+        }
+    }
+
+    /// Handle a key event coming from the main UI.
     pub fn handle_key_event(&mut self, key_event: KeyEvent) -> (InputResult, bool) {
+        let result = match self.command_popup {
+            Some(_) => self.handle_key_event_with_popup(key_event),
+            None => self.handle_key_event_without_popup(key_event),
+        };
+
+        // Update (or hide/show) popup after processing the key.
+        self.sync_command_popup();
+
+        result
+    }
+
+    /// Handle key event when the slash-command popup is visible.
+    fn handle_key_event_with_popup(&mut self, key_event: KeyEvent) -> (InputResult, bool) {
+        let Some(popup) = self.command_popup.as_mut() else {
+            tracing::error!("handle_key_event_with_popup called without an active popup");
+            return (InputResult::None, false);
+        };
+
         match key_event.into() {
+            Input { key: Key::Up, .. } => {
+                popup.move_up();
+                (InputResult::None, true)
+            }
+            Input { key: Key::Down, .. } => {
+                popup.move_down();
+                (InputResult::None, true)
+            }
+            Input { key: Key::Tab, .. } => {
+                if let Some(cmd) = popup.selected_command() {
+                    let first_line = self
+                        .textarea
+                        .lines()
+                        .first()
+                        .map(|s| s.as_str())
+                        .unwrap_or("");
+
+                    let starts_with_cmd = first_line
+                        .trim_start()
+                        .starts_with(&format!("/{}", cmd.command()));
+
+                    if !starts_with_cmd {
+                        self.textarea.select_all();
+                        self.textarea.cut();
+                        let _ = self
+                            .textarea
+                            .insert_str(format!("/{} ", cmd.command()));
+                    }
+
+                    // hide popup
+                    self.command_popup = None;
+                }
+                (InputResult::None, true)
+            }
+            Input {
+                key: Key::Enter,
+                shift: false,
+                alt: false,
+                ctrl: false,
+            } => {
+                if let Some(cmd) = popup.selected_command() {
+                    // TODO: actually run command instead of submitting it to the model.
+                    let _command_text = format!("/{}", cmd.command());
+                    self.textarea.select_all();
+                    self.textarea.cut();
+                    // Hide popup since command has been handled.
+                    self.command_popup = None;
+                    return (InputResult::None, true);
+                }
+                // Fallback to default newline handling if no command selected.
+                self.handle_key_event_without_popup(key_event)
+            }
+            input => self.handle_input_basic(input),
+        }
+    }
+
+    /// Handle key event when no popup is visible.
+    fn handle_key_event_without_popup(&mut self, key_event: KeyEvent) -> (InputResult, bool) {
+        let input: Input = key_event.into();
+        match input {
             Input {
                 key: Key::Enter,
                 shift: false,
@@ -69,16 +182,25 @@ impl ChatComposer<'_> {
                 self.textarea.insert_newline();
                 (InputResult::None, true)
             }
-            input => {
-                self.textarea.input(input);
-                (InputResult::None, true)
-            }
+            input => self.handle_input_basic(input),
         }
     }
 
+    /// Handle generic Input events that modify the textarea content.
+    fn handle_input_basic(&mut self, input: Input) -> (InputResult, bool) {
+        self.textarea.input(input);
+        (InputResult::None, true)
+    }
+
     pub fn calculate_required_height(&self, _area: &Rect) -> u16 {
         let rows = self.textarea.lines().len().max(MIN_TEXTAREA_ROWS);
-        rows as u16 + BORDER_LINES
+        let mut total = rows as u16 + BORDER_LINES;
+
+        if let Some(popup) = &self.command_popup {
+            total += popup.calculate_required_height(_area);
+        }
+
+        total
     }
 
     fn update_border(&mut self, has_focus: bool) {
@@ -108,10 +230,37 @@ impl ChatComposer<'_> {
                 .border_style(bs.border_style),
         );
     }
+
+    pub(crate) fn is_command_popup_visible(&self) -> bool {
+        self.command_popup.is_some()
+    }
 }
 
 impl WidgetRef for &ChatComposer<'_> {
     fn render_ref(&self, area: Rect, buf: &mut Buffer) {
-        self.textarea.render(area, buf);
+        if let Some(popup) = &self.command_popup {
+            let popup_height = popup.calculate_required_height(&area);
+
+            // Split the provided rect so that the popup is rendered at the
+            // *top* and the textarea occupies the remaining space below.
+            let popup_rect = Rect {
+                x: area.x,
+                y: area.y,
+                width: area.width,
+                height: popup_height.min(area.height),
+            };
+
+            let textarea_rect = Rect {
+                x: area.x,
+                y: area.y + popup_rect.height,
+                width: area.width,
+                height: area.height.saturating_sub(popup_rect.height),
+            };
+
+            popup.render(popup_rect, buf);
+            self.textarea.render(textarea_rect, buf);
+        } else {
+            self.textarea.render(area, buf);
+        }
     }
 }
diff --git a/codex-rs/tui/src/bottom_pane/command_popup.rs b/codex-rs/tui/src/bottom_pane/command_popup.rs
new file mode 100644
index 0000000000..d9e7c5634b
--- /dev/null
+++ b/codex-rs/tui/src/bottom_pane/command_popup.rs
@@ -0,0 +1,185 @@
+use std::collections::HashMap;
+
+use ratatui::buffer::Buffer;
+use ratatui::layout::Rect;
+use ratatui::widgets::WidgetRef;
+
+use crate::slash_command::SlashCommand;
+use crate::slash_command::built_in_slash_commands;
+
+const MAX_POPUP_ROWS: usize = 5;
+
+use ratatui::style::Modifier;
+
+pub(crate) struct CommandPopup {
+    command_filter: String,
+    all_commands: HashMap<String, SlashCommand>,
+    selected_idx: Option<usize>,
+}
+
+impl CommandPopup {
+    pub(crate) fn new() -> Self {
+        Self {
+            command_filter: String::new(),
+            all_commands: built_in_slash_commands(),
+            selected_idx: None,
+        }
+    }
+
+    /// Update the filter string based on the current composer text. The text
+    /// passed in is expected to start with a leading '/'. Everything after the
+    /// *first* '/" on the *first* line becomes the active filter that is used
+    /// to narrow down the list of available commands.
+    pub(crate) fn on_composer_text_change(&mut self, text: String) {
+        let first_line = text.lines().next().unwrap_or("");
+
+        if let Some(stripped) = first_line.strip_prefix('/') {
+            // Extract the *first* token (sequence of non-whitespace
+            // characters) after the slash so that `/clear something` still
+            // shows the help for `/clear`.
+            let token = stripped.trim_start();
+            let cmd_token = token.split_whitespace().next().unwrap_or("");
+
+            // Update the filter keeping the original case (commands are all
+            // lower-case for now but this may change in the future).
+            self.command_filter = cmd_token.to_string();
+        } else {
+            // The composer no longer starts with '/'. Reset the filter so the
+            // popup shows the *full* command list if it is still displayed
+            // for some reason.
+            self.command_filter.clear();
+        }
+
+        // Reset or clamp selected index based on new filtered list.
+        let matches_len = self.filtered_commands().len();
+        self.selected_idx = match matches_len {
+            0 => None,
+            _ => Some(self.selected_idx.unwrap_or(0).min(matches_len - 1)),
+        };
+    }
+
+    /// Determine the preferred height of the popup. This is the number of
+    /// rows required to show **at most** `MAX_POPUP_ROWS` commands plus the
+    /// table/border overhead (one line at the top and one at the bottom).
+    pub(crate) fn calculate_required_height(&self, _area: &Rect) -> u16 {
+        let matches = self.filtered_commands();
+        let row_count = matches.len().clamp(1, MAX_POPUP_ROWS) as u16;
+        // Account for the border added by the Block that wraps the table.
+        // 2 = one line at the top, one at the bottom.
+        row_count + 2
+    }
+
+    /// Return the list of commands that match the current filter. Matching is
+    /// performed using a *prefix* comparison on the command name.
+    fn filtered_commands(&self) -> Vec<&SlashCommand> {
+        let mut cmds: Vec<&SlashCommand> = self
+            .all_commands
+            .values()
+            .filter(|cmd| {
+                if self.command_filter.is_empty() {
+                    true
+                } else {
+                    cmd.command()
+                        .starts_with(&self.command_filter.to_ascii_lowercase())
+                }
+            })
+            .collect();
+
+        // Sort the commands alphabetically so the order is stable and
+        // predictable.
+        cmds.sort_by(|a, b| a.command().cmp(b.command()));
+        cmds
+    }
+
+    /// Move the selection cursor one step up.
+    pub(crate) fn move_up(&mut self) {
+        if let Some(len) = self.filtered_commands().len().checked_sub(1) {
+            if len == usize::MAX {
+                return;
+            }
+        }
+
+        if let Some(idx) = self.selected_idx {
+            if idx > 0 {
+                self.selected_idx = Some(idx - 1);
+            }
+        } else if !self.filtered_commands().is_empty() {
+            self.selected_idx = Some(0);
+        }
+    }
+
+    /// Move the selection cursor one step down.
+    pub(crate) fn move_down(&mut self) {
+        let matches_len = self.filtered_commands().len();
+        if matches_len == 0 {
+            self.selected_idx = None;
+            return;
+        }
+
+        match self.selected_idx {
+            Some(idx) if idx + 1 < matches_len => {
+                self.selected_idx = Some(idx + 1);
+            }
+            None => {
+                self.selected_idx = Some(0);
+            }
+            _ => {}
+        }
+    }
+
+    /// Return currently selected command, if any.
+    pub(crate) fn selected_command(&self) -> Option<&SlashCommand> {
+        let matches = self.filtered_commands();
+        self.selected_idx
+            .and_then(|idx| matches.get(idx).copied())
+    }
+}
+
+impl WidgetRef for CommandPopup {
+    fn render_ref(&self, area: Rect, buf: &mut Buffer) {
+        use ratatui::style::{Color, Style};
+        use ratatui::widgets::{Block, Borders, BorderType, Cell, Row, Table, Widget};
+
+        let style = Style::default().bg(Color::Blue).fg(Color::White);
+
+        let matches = self.filtered_commands();
+
+        let mut rows: Vec<Row> = Vec::new();
+        let visible_matches: Vec<&SlashCommand> = matches.into_iter().take(MAX_POPUP_ROWS).collect();
+
+        if visible_matches.is_empty() {
+            rows.push(Row::new(vec![
+                Cell::from("").style(style),
+                Cell::from("No matching commands").style(style.add_modifier(Modifier::ITALIC)),
+            ]));
+        } else {
+            for (idx, cmd) in visible_matches.iter().enumerate() {
+                let highlight = Style::default().bg(Color::White).fg(Color::Blue);
+                let cmd_style = if Some(idx) == self.selected_idx {
+                    highlight
+                } else {
+                    style
+                };
+
+                rows.push(Row::new(vec![
+                    Cell::from(cmd.command().to_string()).style(cmd_style),
+                    Cell::from(cmd.description().to_string()).style(style),
+                ]));
+            }
+        }
+
+        use ratatui::layout::Constraint;
+
+        let table = Table::new(rows, [Constraint::Length(15), Constraint::Min(10)])
+            .style(style)
+            .column_spacing(1)
+            .block(
+                Block::default()
+                    .borders(Borders::ALL)
+                    .border_type(BorderType::Rounded)
+                    .style(style),
+            );
+
+        table.render(area, buf);
+    }
+}
diff --git a/codex-rs/tui/src/bottom_pane/mod.rs b/codex-rs/tui/src/bottom_pane/mod.rs
index ca606428ae..1466ddf423 100644
--- a/codex-rs/tui/src/bottom_pane/mod.rs
+++ b/codex-rs/tui/src/bottom_pane/mod.rs
@@ -15,6 +15,7 @@ use crate::user_approval_widget::ApprovalRequest;
 mod approval_modal_view;
 mod bottom_pane_view;
 mod chat_composer;
+mod command_popup;
 mod status_indicator_view;
 
 pub(crate) use chat_composer::ChatComposer;
@@ -168,6 +169,11 @@ impl BottomPane<'_> {
     pub(crate) fn request_redraw(&self) -> Result<(), SendError<AppEvent>> {
         self.app_event_tx.send(AppEvent::Redraw)
     }
+
+    /// Returns true when the slash-command popup inside the composer is visible.
+    pub(crate) fn is_command_popup_visible(&self) -> bool {
+        self.active_view.is_none() && self.composer.is_command_popup_visible()
+    }
 }
 
 impl WidgetRef for &BottomPane<'_> {
diff --git a/codex-rs/tui/src/chatwidget.rs b/codex-rs/tui/src/chatwidget.rs
index c7ffe73431..4794885570 100644
--- a/codex-rs/tui/src/chatwidget.rs
+++ b/codex-rs/tui/src/chatwidget.rs
@@ -124,8 +124,12 @@ impl ChatWidget<'_> {
         &mut self,
         key_event: KeyEvent,
     ) -> std::result::Result<(), SendError<AppEvent>> {
-        // Special-case <tab>: does not get dispatched to child components.
-        if matches!(key_event.code, crossterm::event::KeyCode::Tab) {
+        // Special-case <Tab>: normally toggles focus between history and bottom panes.
+        // However, when the slash-command popup is visible we forward the key
+        // to the bottom pane so it can handle auto-completion.
+        if matches!(key_event.code, crossterm::event::KeyCode::Tab)
+            && !self.bottom_pane.is_command_popup_visible()
+        {
             self.input_focus = match self.input_focus {
                 InputFocus::HistoryPane => InputFocus::BottomPane,
                 InputFocus::BottomPane => InputFocus::HistoryPane,
diff --git a/codex-rs/tui/src/lib.rs b/codex-rs/tui/src/lib.rs
index e0b6274c7d..3d339d26a1 100644
--- a/codex-rs/tui/src/lib.rs
+++ b/codex-rs/tui/src/lib.rs
@@ -26,6 +26,7 @@ mod history_cell;
 mod log_layer;
 mod markdown;
 mod scroll_event_helper;
+mod slash_command;
 mod status_indicator_widget;
 mod tui;
 mod user_approval_widget;
diff --git a/codex-rs/tui/src/slash_command.rs b/codex-rs/tui/src/slash_command.rs
new file mode 100644
index 0000000000..96774c873d
--- /dev/null
+++ b/codex-rs/tui/src/slash_command.rs
@@ -0,0 +1,48 @@
+use std::collections::HashMap;
+
+/// Command that can be invoked via the composer by starting the message with a
+/// slash followed by the command name.
+#[derive(Debug, Clone)]
+pub struct SlashCommand {
+    /// Command name without the leading slash.
+    command: &'static str,
+
+    /// Command description suitable for display in the UI.
+    description: &'static str,
+}
+
+impl SlashCommand {
+    /// Return the command string without the leading slash.
+    pub fn command(&self) -> &str {
+        self.command
+    }
+
+    /// Return the human-readable description for the command.
+    pub fn description(&self) -> &str {
+        self.description
+    }
+}
+
+pub fn built_in_slash_commands() -> HashMap<String, SlashCommand> {
+    vec![
+        SlashCommand {
+            command: "help",
+            description: "Show this help message.",
+        },
+        SlashCommand {
+            command: "clear",
+            description: "Clear the chat history.",
+        },
+        SlashCommand {
+            command: "reset",
+            description: "Reset the chat history.",
+        },
+        SlashCommand {
+            command: "exit",
+            description: "Exit the application.",
+        },
+    ]
+    .into_iter()
+    .map(|cmd| (cmd.command.to_owned(), cmd))
+    .collect::<HashMap<String, SlashCommand>>()
+}