fix(input): preserve shift-tab in pane automation (#2259)

refs #1561

3 files changed, 63 insertions, 1 deletions

diff --git a/src/app/api/panes.rs b/src/app/api/panes.rs
index 72798a1b..a5f1cbcb 100644
--- a/src/app/api/panes.rs
+++ b/src/app/api/panes.rs
@@ -1979,6 +1979,24 @@ mod tests {
     }
 
     #[tokio::test]
+    async fn api_pane_send_keys_encodes_shift_tab_as_backtab() {
+        let (mut app, pane_id, mut rx) = app_with_send_key_runtime(1);
+
+        let response = app.handle_api_request(crate::api::schema::Request {
+            id: "req".into(),
+            method: crate::api::schema::Method::PaneSendKeys(PaneSendKeysParams {
+                pane_id,
+                keys: vec!["shift+tab".into()],
+            }),
+        });
+
+        let success: SuccessResponse = serde_json::from_str(&response).unwrap();
+        assert_eq!(success.result, ResponseResult::Ok {});
+        assert_eq!(rx.try_recv().unwrap(), bytes::Bytes::from_static(b"\x1b[Z"));
+        assert!(rx.try_recv().is_err());
+    }
+
+    #[tokio::test]
     async fn api_pane_get_exposes_scroll_metrics() {
         let (mut app, public_pane_id, pane_id) = app_with_scrollback_runtime();
         let runtime = app
diff --git a/src/pane/input.rs b/src/pane/input.rs
index 38e8138b..2e60bfc8 100644
--- a/src/pane/input.rs
+++ b/src/pane/input.rs
@@ -13,7 +13,12 @@ pub(super) fn ghostty_key_event_from_terminal_key(
             crate::ghostty::ffi::GhosttyKeyAction_GHOSTTY_KEY_ACTION_REPEAT
         }
     });
-    event.set_mods(ghostty_mods_from_key_modifiers(key.modifiers));
+    let mut mods = ghostty_mods_from_key_modifiers(key.modifiers);
+    if matches!(key.code, crossterm::event::KeyCode::BackTab) {
+        // Ghostty represents backtab as Tab with Shift rather than a distinct key.
+        mods |= crate::ghostty::MOD_SHIFT;
+    }
+    event.set_mods(mods);
     event.set_key(ghostty_key_from_crossterm_key_code(
         key.code,
         key.shifted_codepoint,
diff --git a/src/pane/terminal.rs b/src/pane/terminal.rs
index b90c63f1..d4f167a9 100644
--- a/src/pane/terminal.rs
+++ b/src/pane/terminal.rs
@@ -3857,6 +3857,45 @@ mod tests {
     }
 
     #[test]
+    fn ghostty_backtab_preserves_shift_across_keyboard_protocols() {
+        for (kitty_flags, expected) in [
+            (None, b"\x1b[Z".as_slice()),
+            (Some(1), b"\x1b[9;2u".as_slice()),
+        ] {
+            let (tx, _rx) = mpsc::channel(4);
+            let mut terminal = crate::ghostty::Terminal::new(80, 24, 0).unwrap();
+            if let Some(flags) = kitty_flags {
+                terminal.write(format!("\x1b[>{flags}u").as_bytes());
+            }
+            let pane = GhosttyPaneTerminal::new(terminal, tx).unwrap();
+            let protocol = pane.keyboard_protocol().unwrap();
+
+            for modifiers in [
+                crossterm::event::KeyModifiers::empty(),
+                crossterm::event::KeyModifiers::SHIFT,
+            ] {
+                let encoded = pane.encode_terminal_key(
+                    crate::input::TerminalKey::new(crossterm::event::KeyCode::BackTab, modifiers),
+                    protocol,
+                );
+                assert_eq!(encoded, expected, "backtab with modifiers {modifiers:?}");
+            }
+        }
+
+        let (tx, _rx) = mpsc::channel(4);
+        let terminal = crate::ghostty::Terminal::new(80, 24, 0).unwrap();
+        let pane = GhosttyPaneTerminal::new(terminal, tx).unwrap();
+        let encoded = pane.encode_terminal_key(
+            crate::input::TerminalKey::new(
+                crossterm::event::KeyCode::Tab,
+                crossterm::event::KeyModifiers::empty(),
+            ),
+            crate::input::KeyboardProtocol::Legacy,
+        );
+        assert_eq!(encoded, b"\t");
+    }
+
+    #[test]
     fn ghostty_enter_backspace_release_in_legacy_pane_emits_nothing() {
         let (tx, _rx) = mpsc::channel(4);
         let terminal = crate::ghostty::Terminal::new(80, 24, 0).unwrap();