fix(cli): disable auto-completion on Shift+Tab to preserve mode cycling (#19451)

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

@@ -1221,6 +1221,36 @@ describe('InputPrompt', () => {
     unmount();
   });
 
+  it('should NOT autocomplete on Shift+Tab', async () => {
+    const suggestion = { label: 'about', value: 'about' };
+
+    mockedUseCommandCompletion.mockReturnValue({
+      ...mockCommandCompletion,
+      showSuggestions: true,
+      suggestions: [suggestion],
+      activeSuggestionIndex: 0,
+      getCompletedText: vi.fn().mockReturnValue('/about'),
+    });
+
+    props.buffer.setText('/ab');
+    props.buffer.lines = ['/ab'];
+    props.buffer.cursor = [0, 3];
+
+    const { stdin, unmount } = renderWithProviders(<InputPrompt {...props} />, {
+      uiActions,
+    });
+
+    await act(async () => {
+      stdin.write('\x1b[Z'); // Shift+Tab
+    });
+
+    // We need to wait a bit to ensure handleAutocomplete was NOT called
+    await new Promise((resolve) => setTimeout(resolve, 100));
+
+    expect(mockCommandCompletion.handleAutocomplete).not.toHaveBeenCalled();
+    unmount();
+  });
+
   it('should autocomplete custom commands from .toml files on Enter', async () => {
     const customCommand: SlashCommand = {
       name: 'find-capital',
@@ -2659,6 +2689,38 @@ describe('InputPrompt', () => {
       unmount();
     }, 15000);
 
+    it('should NOT autocomplete on Shift+Tab in reverse search', async () => {
+      const mockHandleAutocomplete = vi.fn();
+
+      mockedUseReverseSearchCompletion.mockReturnValue({
+        ...mockReverseSearchCompletion,
+        suggestions: [{ label: 'echo hello', value: 'echo hello' }],
+        showSuggestions: true,
+        activeSuggestionIndex: 0,
+        handleAutocomplete: mockHandleAutocomplete,
+      });
+
+      const { stdin, unmount } = renderWithProviders(
+        <InputPrompt {...props} />,
+        {
+          uiActions,
+        },
+      );
+
+      await act(async () => {
+        stdin.write('\x12'); // Ctrl+R
+      });
+
+      await act(async () => {
+        stdin.write('\x1b[Z'); // Shift+Tab
+      });
+
+      await new Promise((resolve) => setTimeout(resolve, 100));
+
+      expect(mockHandleAutocomplete).not.toHaveBeenCalled();
+      unmount();
+    });
+
     it('submits the highlighted entry on Enter and exits reverse-search', async () => {
       // Mock the reverse search completion to return suggestions
       mockedUseReverseSearchCompletion.mockReturnValue({
@@ -3035,6 +3097,39 @@ describe('InputPrompt', () => {
       },
     );
 
+    it('should NOT accept ghost text on Shift+Tab', async () => {
+      const mockAccept = vi.fn();
+      mockedUseCommandCompletion.mockReturnValue({
+        ...mockCommandCompletion,
+        showSuggestions: false,
+        suggestions: [],
+        promptCompletion: {
+          text: 'ghost text',
+          accept: mockAccept,
+          clear: vi.fn(),
+          isLoading: false,
+          isActive: true,
+          markSelected: vi.fn(),
+        },
+      });
+
+      const { stdin, unmount } = renderWithProviders(
+        <InputPrompt {...props} />,
+        {
+          uiActions,
+        },
+      );
+
+      await act(async () => {
+        stdin.write('\x1b[Z'); // Shift+Tab
+      });
+
+      await new Promise((resolve) => setTimeout(resolve, 100));
+
+      expect(mockAccept).not.toHaveBeenCalled();
+      unmount();
+    });
+
     it('should not reveal clean UI details on Shift+Tab when hidden', async () => {
       mockedUseCommandCompletion.mockReturnValue({
         ...mockCommandCompletion,

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

@@ -975,6 +975,7 @@ export const InputPrompt: React.FC<InputPromptProps> = ({
       // Handle Tab key for ghost text acceptance
       if (
         key.name === 'tab' &&
+        !key.shift &&
         !completion.showSuggestions &&
         completion.promptCompletion.text
       ) {