feat(tui): add /app desktop handoff

codex-rs/tui/src/app/event_dispatch.rs

@@ -403,6 +403,9 @@ impl App {
             AppEvent::OpenUrlInBrowser { url } => {
                 self.open_url_in_browser(url);
             }
+            AppEvent::OpenDesktopThread { thread_id } => {
+                self.open_desktop_thread(thread_id);
+            }
             AppEvent::PetSelected { pet_id } => {
                 self.handle_pet_selected(tui, pet_id);
             }

codex-rs/tui/src/app/history_ui.rs

@@ -1,10 +1,12 @@
-//! Terminal history and clear-screen UI helpers for the TUI app.
+//! Terminal history, desktop handoff, and clear-screen UI helpers for the TUI app.
 //!
 //! This module owns rendering the fresh session header, clearing inline or alternate-screen UI
 //! state, and resetting transcript-related app state after `/clear` or Ctrl-L.
 
 use super::*;
 
+const DESKTOP_THREAD_OPENED_MESSAGE: &str = "Opened this session in Codex Desktop.";
+
 impl App {
     pub(super) fn open_url_in_browser(&mut self, url: String) {
         if let Err(err) = webbrowser::open(&url) {
@@ -17,6 +19,20 @@ impl App {
             .add_info_message(format!("Opened {url} in your browser."), /*hint*/ None);
     }
 
+    pub(super) fn open_desktop_thread(&mut self, thread_id: ThreadId) {
+        let url = format!("codex://threads/{thread_id}");
+        if let Err(err) = open_desktop_thread_url(&url) {
+            self.chat_widget
+                .add_error_message(desktop_thread_open_error_message(&err));
+            return;
+        }
+
+        self.chat_widget.add_info_message(
+            DESKTOP_THREAD_OPENED_MESSAGE.to_string(),
+            /*hint*/ None,
+        );
+    }
+
     pub(super) fn clear_ui_header_lines_with_version(
         &self,
         width: u16,
@@ -99,3 +115,93 @@ impl App {
         self.backtrack_render_pending = false;
     }
 }
+
+fn desktop_thread_open_error_message(err: &str) -> String {
+    format!(
+        "Failed to open this session in Codex Desktop: {err}. Install or launch Codex Desktop and try again."
+    )
+}
+
+#[cfg(target_os = "macos")]
+fn open_desktop_thread_url(url: &str) -> Result<(), String> {
+    let status = std::process::Command::new("open")
+        .arg(url)
+        .status()
+        .map_err(|err| format!("failed to invoke `open`: {err}"))?;
+
+    if status.success() {
+        Ok(())
+    } else {
+        Err(format!("`open {url}` exited with {status}"))
+    }
+}
+
+#[cfg(target_os = "windows")]
+fn open_desktop_thread_url(url: &str) -> Result<(), String> {
+    let script = windows_desktop_app_launch_script(url);
+    let output = std::process::Command::new("powershell.exe")
+        .arg("-NoProfile")
+        .arg("-Command")
+        .arg(&script)
+        .output()
+        .map_err(|err| format!("failed to launch Codex Desktop through PowerShell: {err}"))?;
+
+    if output.status.success() {
+        return Ok(());
+    }
+
+    let stderr = String::from_utf8_lossy(&output.stderr).trim().to_string();
+    if stderr.is_empty() {
+        Err(format!(
+            "failed to launch Codex Desktop through PowerShell with {}",
+            output.status
+        ))
+    } else {
+        Err(stderr)
+    }
+}
+
+#[cfg(target_os = "windows")]
+fn windows_desktop_app_launch_script(url: &str) -> String {
+    let url = powershell_single_quoted_string(url);
+    format!(
+        r#"
+$ErrorActionPreference = 'Stop'
+$url = {url}
+
+$installLocation = (Get-AppxPackage -Name OpenAI.Codex -ErrorAction SilentlyContinue).InstallLocation
+if ([string]::IsNullOrWhiteSpace($installLocation)) {{
+    Write-Error 'Codex Desktop package is not installed'
+    exit 1
+}}
+
+$appDir = Join-Path $installLocation 'app'
+$exe = Join-Path $appDir 'Codex.exe'
+$app = Join-Path $appDir 'resources\app.asar'
+if (-not (Test-Path $exe)) {{
+    Write-Error "Codex Desktop executable not found at $exe"
+    exit 1
+}}
+if (-not (Test-Path $app)) {{
+    Write-Error "Codex Desktop app bundle not found at $app"
+    exit 1
+}}
+
+Start-Process -FilePath $exe -WorkingDirectory $appDir -ArgumentList @('resources\app.asar', $url)
+"#
+    )
+}
+
+#[cfg(target_os = "windows")]
+fn powershell_single_quoted_string(value: &str) -> String {
+    format!("'{}'", value.replace('\'', "''"))
+}
+
+#[cfg(not(any(target_os = "macos", target_os = "windows")))]
+fn open_desktop_thread_url(_url: &str) -> Result<(), String> {
+    Err("Codex Desktop is only available on macOS and Windows".to_string())
+}
+
+#[cfg(test)]
+#[path = "history_ui_tests.rs"]
+mod tests;

codex-rs/tui/src/app/history_ui_tests.rs

@@ -0,0 +1,29 @@
+use super::*;
+use crate::history_cell;
+use crate::history_cell::HistoryCell;
+
+#[test]
+fn desktop_thread_opened_history_snapshot() {
+    let cell = history_cell::new_info_event(
+        DESKTOP_THREAD_OPENED_MESSAGE.to_string(),
+        /*hint*/ None,
+    );
+
+    insta::assert_snapshot!("desktop_thread_opened_history", render_cell(&cell));
+}
+
+#[test]
+fn desktop_thread_open_error_history_snapshot() {
+    let cell = history_cell::new_error_event(desktop_thread_open_error_message("launch failed"));
+
+    insta::assert_snapshot!("desktop_thread_open_error_history", render_cell(&cell));
+}
+
+fn render_cell(cell: &impl HistoryCell) -> String {
+    let lines = cell.display_lines(/*width*/ 80);
+    lines
+        .iter()
+        .map(ToString::to_string)
+        .collect::<Vec<_>>()
+        .join("\n")
+}

codex-rs/tui/src/app/snapshots/codex_tui__app__history_ui__tests__desktop_thread_open_error_history.snap

@@ -0,0 +1,5 @@
+---
+source: tui/src/app/history_ui_tests.rs
+expression: render_cell(&cell)
+---
+■ Failed to open this session in Codex Desktop: launch failed. Install or launch Codex Desktop and try again.

codex-rs/tui/src/app/snapshots/codex_tui__app__history_ui__tests__desktop_thread_opened_history.snap

@@ -0,0 +1,5 @@
+---
+source: tui/src/app/history_ui_tests.rs
+expression: render_cell(&cell)
+---
+• Opened this session in Codex Desktop.

codex-rs/tui/src/app_event.rs

@@ -330,6 +330,11 @@ pub(crate) enum AppEvent {
         url: String,
     },
 
+    /// Open the current thread in Codex Desktop.
+    OpenDesktopThread {
+        thread_id: ThreadId,
+    },
+
     /// Persist a pet selection and reload the ambient pet.
     PetSelected {
         pet_id: String,

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

@@ -393,6 +393,25 @@ mod tests {
         );
     }
 
+    #[cfg(any(target_os = "macos", target_os = "windows"))]
+    #[test]
+    fn app_command_popup_snapshot() {
+        let mut popup = CommandPopup::new(CommandPopupFlags::default(), Vec::new());
+        popup.on_composer_text_change("/app".to_string());
+
+        let width = 72;
+        let area = Rect::new(
+            /*x*/ 0,
+            /*y*/ 0,
+            width,
+            popup.calculate_required_height(width),
+        );
+        let mut buf = Buffer::empty(area);
+        popup.render_ref(area, &mut buf);
+
+        insta::assert_snapshot!("command_popup_app", format!("{buf:?}"));
+    }
+
     #[test]
     fn prefix_filter_limits_matches_for_ac() {
         let mut popup = CommandPopup::new(CommandPopupFlags::default(), Vec::new());

codex-rs/tui/src/bottom_pane/snapshots/codex_tui__bottom_pane__command_popup__tests__command_popup_app.snap

@@ -0,0 +1,20 @@
+---
+source: tui/src/bottom_pane/command_popup.rs
+expression: "format!(\"{buf:?}\")"
+---
+Buffer {
+    area: Rect { x: 0, y: 0, width: 72, height: 2 },
+    content: [
+        "  /app      continue this session in Codex Desktop                      ",
+        "  /approve  approve one retry of a recent auto-review denial            ",
+    ],
+    styles: [
+        x: 0, y: 0, fg: Reset, bg: Reset, underline: Reset, modifier: NONE,
+        x: 2, y: 0, fg: Cyan, bg: Reset, underline: Reset, modifier: BOLD,
+        x: 50, y: 0, fg: Reset, bg: Reset, underline: Reset, modifier: NONE,
+        x: 3, y: 1, fg: Reset, bg: Reset, underline: Reset, modifier: BOLD,
+        x: 6, y: 1, fg: Reset, bg: Reset, underline: Reset, modifier: NONE,
+        x: 12, y: 1, fg: Reset, bg: Reset, underline: Reset, modifier: DIM,
+        x: 60, y: 1, fg: Reset, bg: Reset, underline: Reset, modifier: NONE,
+    ]
+}

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

@@ -202,6 +202,16 @@ impl ChatWidget {
             SlashCommand::Fork => {
                 self.app_event_tx.send(AppEvent::ForkCurrentSession);
             }
+            SlashCommand::App => {
+                let Some(thread_id) = self.thread_id else {
+                    self.add_error_message(
+                        "Session is still starting; try /app again in a moment.".to_string(),
+                    );
+                    return;
+                };
+                self.app_event_tx
+                    .send(AppEvent::OpenDesktopThread { thread_id });
+            }
             SlashCommand::Init => {
                 let init_target = self.config.cwd.join(DEFAULT_AGENTS_MD_FILENAME);
                 if init_target.exists() {
@@ -974,6 +984,7 @@ impl ChatWidget {
             | SlashCommand::Raw
             | SlashCommand::Vim
             | SlashCommand::Diff
+            | SlashCommand::App
             | SlashCommand::Rename
             | SlashCommand::TestApproval => QueueDrain::Continue,
             SlashCommand::Feedback

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

@@ -0,0 +1,5 @@
+---
+source: tui/src/chatwidget/tests/slash_commands.rs
+expression: "lines_to_single_string(&cells[0])"
+---
+■ Session is still starting; try /app again in a moment.

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

@@ -2052,6 +2052,36 @@ async fn slash_fork_requests_current_fork() {
     assert_matches!(rx.try_recv(), Ok(AppEvent::ForkCurrentSession));
 }
 
+#[tokio::test]
+async fn slash_app_requests_desktop_handoff() {
+    let (mut chat, mut rx, _op_rx) = make_chatwidget_manual(/*model_override*/ None).await;
+    let thread_id = ThreadId::new();
+    chat.thread_id = Some(thread_id);
+
+    chat.dispatch_command(SlashCommand::App);
+
+    assert_matches!(
+        rx.try_recv(),
+        Ok(AppEvent::OpenDesktopThread {
+            thread_id: actual_thread_id,
+        }) if actual_thread_id == thread_id
+    );
+}
+
+#[tokio::test]
+async fn slash_app_without_thread_id_shows_starting_error() {
+    let (mut chat, mut rx, _op_rx) = make_chatwidget_manual(/*model_override*/ None).await;
+
+    chat.dispatch_command(SlashCommand::App);
+
+    let cells = drain_insert_history(&mut rx);
+    assert_eq!(cells.len(), 1, "expected app startup error");
+    assert_chatwidget_snapshot!(
+        "slash_app_without_thread_id_shows_starting_error",
+        lines_to_single_string(&cells[0])
+    );
+}
+
 #[tokio::test]
 async fn slash_rollout_displays_current_path() {
     let (mut chat, mut rx, _op_rx) = make_chatwidget_manual(/*model_override*/ None).await;

codex-rs/tui/src/slash_command.rs

@@ -33,6 +33,7 @@ pub enum SlashCommand {
     Archive,
     Resume,
     Fork,
+    App,
     Init,
     Compact,
     Plan,
@@ -90,6 +91,7 @@ impl SlashCommand {
             SlashCommand::Archive => "archive this session and exit",
             SlashCommand::Clear => "clear the terminal and start a new chat",
             SlashCommand::Fork => "fork the current chat",
+            SlashCommand::App => "continue this session in Codex Desktop",
             SlashCommand::Quit | SlashCommand::Exit => "exit Codex",
             SlashCommand::Copy => "copy last response as markdown",
             SlashCommand::Raw => "toggle raw scrollback mode for copy-friendly terminal selection",
@@ -213,6 +215,7 @@ impl SlashCommand {
             | SlashCommand::DebugConfig
             | SlashCommand::Ps
             | SlashCommand::Stop
+            | SlashCommand::App
             | SlashCommand::Goal
             | SlashCommand::Mcp
             | SlashCommand::Apps
@@ -239,6 +242,7 @@ impl SlashCommand {
         match self {
             SlashCommand::SandboxReadRoot => cfg!(target_os = "windows"),
             SlashCommand::Copy => !cfg!(target_os = "android"),
+            SlashCommand::App => cfg!(any(target_os = "macos", target_os = "windows")),
             SlashCommand::Rollout | SlashCommand::TestApproval => cfg!(debug_assertions),
             _ => true,
         }
@@ -285,6 +289,7 @@ mod tests {
         assert!(SlashCommand::Raw.available_during_task());
         assert!(SlashCommand::Raw.available_in_side_conversation());
         assert!(SlashCommand::Raw.supports_inline_args());
+        assert!(SlashCommand::App.available_during_task());
     }
 
     #[test]