fix(cli): allow scrolling keys in copy mode (Ctrl+S selection mode) (#19933)

Co-authored-by: Jacob Richman <jacob314@gmail.com>

packages/cli/src/ui/AppContainer.test.tsx

@@ -2770,7 +2770,7 @@ describe('AppContainer State Management', () => {
           unmount();
         });
 
-        it('should exit copy mode on any key press', async () => {
+        it('should exit copy mode on non-scroll key press', async () => {
           await setupCopyModeTest(isAlternateMode);
 
           // Enter copy mode
@@ -2792,6 +2792,61 @@ describe('AppContainer State Management', () => {
           unmount();
         });
 
+        it('should not exit copy mode on PageDown and should pass it through', async () => {
+          const childHandler = vi.fn().mockReturnValue(false);
+          await setupCopyModeTest(true, childHandler);
+
+          // Enter copy mode
+          act(() => {
+            stdin.write('\x13'); // Ctrl+S
+          });
+          rerender();
+          expect(disableMouseEvents).toHaveBeenCalled();
+
+          childHandler.mockClear();
+          (enableMouseEvents as Mock).mockClear();
+
+          // PageDown should be passed through to lower-priority handlers.
+          act(() => {
+            stdin.write('\x1b[6~');
+          });
+          rerender();
+
+          expect(enableMouseEvents).not.toHaveBeenCalled();
+          expect(childHandler).toHaveBeenCalled();
+          expect(childHandler).toHaveBeenCalledWith(
+            expect.objectContaining({ name: 'pagedown' }),
+          );
+          unmount();
+        });
+
+        it('should not exit copy mode on Shift+Down and should pass it through', async () => {
+          const childHandler = vi.fn().mockReturnValue(false);
+          await setupCopyModeTest(true, childHandler);
+
+          // Enter copy mode
+          act(() => {
+            stdin.write('\x13'); // Ctrl+S
+          });
+          rerender();
+          expect(disableMouseEvents).toHaveBeenCalled();
+
+          childHandler.mockClear();
+          (enableMouseEvents as Mock).mockClear();
+
+          act(() => {
+            stdin.write('\x1b[1;2B'); // Shift+Down
+          });
+          rerender();
+
+          expect(enableMouseEvents).not.toHaveBeenCalled();
+          expect(childHandler).toHaveBeenCalled();
+          expect(childHandler).toHaveBeenCalledWith(
+            expect.objectContaining({ name: 'down', shift: true }),
+          );
+          unmount();
+        });
+
         it('should have higher priority than other priority listeners when enabled', async () => {
           // 1. Initial state with a child component's priority listener (already subscribed)
           // It should NOT handle Ctrl+S so we can enter copy mode.

packages/cli/src/ui/AppContainer.tsx

@@ -1864,7 +1864,18 @@ Logging in with Google... Restarting Gemini CLI to continue.
   useKeypress(handleGlobalKeypress, { isActive: true, priority: true });
 
   useKeypress(
-    () => {
+    (key: Key) => {
+      if (
+        keyMatchers[Command.SCROLL_UP](key) ||
+        keyMatchers[Command.SCROLL_DOWN](key) ||
+        keyMatchers[Command.PAGE_UP](key) ||
+        keyMatchers[Command.PAGE_DOWN](key) ||
+        keyMatchers[Command.SCROLL_HOME](key) ||
+        keyMatchers[Command.SCROLL_END](key)
+      ) {
+        return false;
+      }
+
       setCopyModeEnabled(false);
       enableMouseEvents();
       return true;

packages/cli/src/ui/components/CopyModeWarning.test.tsx

@@ -35,7 +35,8 @@ describe('CopyModeWarning', () => {
     const { lastFrame, waitUntilReady, unmount } = render(<CopyModeWarning />);
     await waitUntilReady();
     expect(lastFrame()).toContain('In Copy Mode');
-    expect(lastFrame()).toContain('Press any key to exit');
+    expect(lastFrame()).toContain('Use Page Up/Down to scroll');
+    expect(lastFrame()).toContain('Press Ctrl+S or any other key to exit');
     unmount();
   });
 });

packages/cli/src/ui/components/CopyModeWarning.tsx

@@ -19,7 +19,8 @@ export const CopyModeWarning: React.FC = () => {
   return (
     <Box>
       <Text color={theme.status.warning}>
-        In Copy Mode. Press any key to exit.
+        In Copy Mode. Use Page Up/Down to scroll. Press Ctrl+S or any other key
+        to exit.
       </Text>
     </Box>
   );