diff --git a/crates/quicproquo-client/src/client/v2_repl.rs b/crates/quicproquo-client/src/client/v2_repl.rs
index 7a1c740..5ea83ec 100644
--- a/crates/quicproquo-client/src/client/v2_repl.rs
+++ b/crates/quicproquo-client/src/client/v2_repl.rs
@@ -937,8 +937,9 @@ async fn do_devices(client: &mut QpqClient, args: &str) -> anyhow::Result<()> {
             }
             let rpc = client.rpc().map_err(|e| anyhow::anyhow!("{e}"))?;
             // Generate a random device ID (16 bytes).
-            use rand::Rng;
-            let dev_id: Vec<u8> = rand::rng().random::<[u8; 16]>().to_vec();
+            use rand::RngCore;
+            let mut dev_id = vec![0u8; 16];
+            rand::rngs::OsRng.fill_bytes(&mut dev_id);
             let was_new =
                 quicproquo_sdk::devices::register_device(rpc, &dev_id, name).await?;
             if was_new {
diff --git a/crates/quicproquo-client/src/client/v2_tui.rs b/crates/quicproquo-client/src/client/v2_tui.rs
index c5a4aca..5ae66e1 100644
--- a/crates/quicproquo-client/src/client/v2_tui.rs
+++ b/crates/quicproquo-client/src/client/v2_tui.rs
@@ -84,6 +84,10 @@ pub struct TuiApp {
     focus: Focus,
     /// Notification line (shown briefly, e.g. "Message sent", "Error: ...").
     notification: Option<String>,
+    /// Whether the client is currently connected.
+    connected: bool,
+    /// Current MLS epoch for the active conversation (if available).
+    mls_epoch: Option<u64>,
 }
 
 impl TuiApp {
@@ -101,6 +105,8 @@ impl TuiApp {
             server_addr: server_addr.to_string(),
             focus: Focus::Input,
             notification: None,
+            connected: false,
+            mls_epoch: None,
         }
     }
 
@@ -140,13 +146,18 @@ impl TuiApp {
     }
 
     fn update_status(&mut self) {
+        let conn_indicator = if self.connected { "Online" } else { "Offline" };
         let user = self
             .username
             .as_deref()
             .unwrap_or("not logged in");
         let conv_count = self.conversations.len();
+        let epoch_str = match self.mls_epoch {
+            Some(e) => format!("epoch {e}"),
+            None => "epoch --".to_string(),
+        };
         self.status_line = format!(
-            "Connected to {} | {} | {} conversation{}",
+            "{conn_indicator} | {} | {} | {} conversation{} | MLS {epoch_str}",
             self.server_addr,
             user,
             conv_count,
@@ -184,6 +195,7 @@ pub async fn run_v2_tui(client: &mut QpqClient) -> anyhow::Result<()> {
         "disconnected"
     };
     let mut app = TuiApp::new(server_addr);
+    app.connected = client.is_connected();
 
     // Populate initial state from client.
     if let Some(name) = client.username() {
@@ -263,12 +275,14 @@ pub async fn run_v2_tui(client: &mut QpqClient) -> anyhow::Result<()> {
 fn handle_sdk_event(app: &mut TuiApp, event: ClientEvent) {
     match event {
         ClientEvent::Connected => {
+            app.connected = true;
             app.notification = Some("Connected to server".to_string());
             app.update_status();
         }
         ClientEvent::Disconnected { reason } => {
-            app.status_line = format!("Disconnected: {reason}");
+            app.connected = false;
             app.notification = Some(format!("Disconnected: {reason}"));
+            app.update_status();
         }
         ClientEvent::Registered { username } => {
             app.notification = Some(format!("Registered as {username}"));
@@ -380,6 +394,8 @@ fn handle_sdk_event(app: &mut TuiApp, event: ClientEvent) {
         ClientEvent::Error { message } => {
             app.notification = Some(format!("Error: {message}"));
         }
+        // Events that don't need TUI-specific handling.
+        _ => {}
     }
 }
 
@@ -818,12 +834,25 @@ fn draw_input(frame: &mut Frame, app: &TuiApp, area: Rect) {
 }
 
 fn draw_status(frame: &mut Frame, app: &TuiApp, area: Rect) {
-    let status = Paragraph::new(Line::from(Span::styled(
-        format!(" {} ", app.status_line),
-        Style::default()
-            .fg(Color::Black)
-            .bg(Color::DarkGray),
-    )));
+    let conn_color = if app.connected {
+        Color::Green
+    } else {
+        Color::Red
+    };
+    let conn_indicator = if app.connected { " ON " } else { " OFF " };
+
+    let spans = vec![
+        Span::styled(
+            conn_indicator,
+            Style::default().fg(Color::Black).bg(conn_color),
+        ),
+        Span::styled(
+            format!(" {} ", app.status_line),
+            Style::default().fg(Color::Black).bg(Color::DarkGray),
+        ),
+    ];
+
+    let status = Paragraph::new(Line::from(spans));
     frame.render_widget(status, area);
 }
 
@@ -977,3 +1006,147 @@ fn now_ms() -> u64 {
         .unwrap_or_default()
         .as_millis() as u64
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use ratatui::{backend::TestBackend, Terminal};
+
+    fn make_app() -> TuiApp {
+        let mut app = TuiApp::new("127.0.0.1:7000");
+        app.connected = true;
+        app.username = Some("alice".to_string());
+        app.conversations.push(ConversationItem {
+            id: [1u8; 16],
+            name: "general".to_string(),
+            unread: 0,
+            last_message: None,
+        });
+        app.conversations.push(ConversationItem {
+            id: [2u8; 16],
+            name: "random".to_string(),
+            unread: 3,
+            last_message: Some("bob: hello".to_string()),
+        });
+        app.messages.push(DisplayMessage {
+            timestamp: "[12:34]".to_string(),
+            sender: "alice".to_string(),
+            body: "Hello world".to_string(),
+            is_outgoing: true,
+        });
+        app.messages.push(DisplayMessage {
+            timestamp: "[12:35]".to_string(),
+            sender: "bob".to_string(),
+            body: "Hi alice!".to_string(),
+            is_outgoing: false,
+        });
+        app.update_status();
+        app
+    }
+
+    #[test]
+    fn render_does_not_panic() {
+        let app = make_app();
+        let backend = TestBackend::new(80, 24);
+        let mut terminal = Terminal::new(backend).unwrap();
+        terminal.draw(|f| ui(f, &app)).unwrap();
+    }
+
+    #[test]
+    fn render_help_overlay() {
+        let mut app = make_app();
+        app.focus = Focus::Help;
+        let backend = TestBackend::new(80, 24);
+        let mut terminal = Terminal::new(backend).unwrap();
+        terminal.draw(|f| ui(f, &app)).unwrap();
+    }
+
+    #[test]
+    fn status_bar_shows_online() {
+        let mut app = TuiApp::new("127.0.0.1:7000");
+        app.connected = true;
+        app.username = Some("alice".to_string());
+        app.update_status();
+        assert!(app.status_line.contains("Online"));
+        assert!(app.status_line.contains("alice"));
+        assert!(app.status_line.contains("MLS epoch --"));
+    }
+
+    #[test]
+    fn status_bar_shows_offline() {
+        let mut app = TuiApp::new("127.0.0.1:7000");
+        app.connected = false;
+        app.update_status();
+        assert!(app.status_line.contains("Offline"));
+    }
+
+    #[test]
+    fn status_bar_shows_epoch() {
+        let mut app = TuiApp::new("127.0.0.1:7000");
+        app.connected = true;
+        app.mls_epoch = Some(42);
+        app.update_status();
+        assert!(app.status_line.contains("MLS epoch 42"));
+    }
+
+    #[test]
+    fn conversation_navigation() {
+        let mut app = make_app();
+        assert_eq!(app.selected_conversation, 0);
+        app.select_next_conversation();
+        assert_eq!(app.selected_conversation, 1);
+        app.select_next_conversation();
+        assert_eq!(app.selected_conversation, 0); // wraps around
+        app.select_prev_conversation();
+        assert_eq!(app.selected_conversation, 1); // wraps back
+    }
+
+    #[test]
+    fn scroll_bounds() {
+        let mut app = make_app();
+        assert_eq!(app.scroll_offset, 0);
+        app.scroll_down(); // already at 0
+        assert_eq!(app.scroll_offset, 0);
+        app.scroll_up();
+        assert_eq!(app.scroll_offset, 1);
+        app.scroll_up();
+        assert_eq!(app.scroll_offset, 2);
+        app.scroll_down();
+        assert_eq!(app.scroll_offset, 1);
+    }
+
+    #[test]
+    fn render_empty_state() {
+        let app = TuiApp::new("127.0.0.1:7000");
+        let backend = TestBackend::new(80, 24);
+        let mut terminal = Terminal::new(backend).unwrap();
+        terminal.draw(|f| ui(f, &app)).unwrap();
+    }
+
+    #[test]
+    fn unread_count_display() {
+        let app = make_app();
+        // The second conversation has 3 unread.
+        assert_eq!(app.conversations[1].unread, 3);
+
+        // Render and check the sidebar contains the unread indicator.
+        let backend = TestBackend::new(80, 24);
+        let mut terminal = Terminal::new(backend).unwrap();
+        terminal.draw(|f| ui(f, &app)).unwrap();
+
+        // Read the buffer and check the sidebar area contains "random (3)".
+        let buf = terminal.backend().buffer().clone();
+        let mut sidebar_text = String::new();
+        // Sidebar is roughly the left 20% = 16 columns.
+        for y in 0..buf.area.height {
+            for x in 0..16.min(buf.area.width) {
+                let cell = &buf[(x, y)];
+                sidebar_text.push_str(cell.symbol());
+            }
+        }
+        assert!(
+            sidebar_text.contains("random (3)"),
+            "sidebar should show unread count; got: {sidebar_text}"
+        );
+    }
+}