feat(cli): improve CTRL+O experience for both standard and alternate screen buffer (ASB) modes (#19010)

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

packages/cli/src/gemini.tsx

@@ -102,6 +102,7 @@ import { createPolicyUpdater } from './config/policy.js';
 import { ScrollProvider } from './ui/contexts/ScrollProvider.js';
 import { isAlternateBufferEnabled } from './ui/hooks/useAlternateBuffer.js';
 import { TerminalProvider } from './ui/contexts/TerminalContext.js';
+import { OverflowProvider } from './ui/contexts/OverflowContext.js';
 
 import { setupTerminalAndTheme } from './utils/terminalTheme.js';
 import { profiler } from './ui/components/DebugProfiler.js';
@@ -238,6 +239,7 @@ export async function startInteractiveUI(
           >
             <TerminalProvider>
               <ScrollProvider>
+                <OverflowProvider>
                   <SessionStatsProvider>
                     <VimModeProvider settings={settings}>
                       <AppContainer
@@ -249,6 +251,7 @@ export async function startInteractiveUI(
                       />
                     </VimModeProvider>
                   </SessionStatsProvider>
+                </OverflowProvider>
               </ScrollProvider>
             </TerminalProvider>
           </MouseProvider>

packages/cli/src/test-utils/render.tsx

@@ -35,6 +35,13 @@ import { type HistoryItemToolGroup, StreamingState } from '../ui/types.js';
 import { ToolActionsProvider } from '../ui/contexts/ToolActionsContext.js';
 import { AskUserActionsProvider } from '../ui/contexts/AskUserActionsContext.js';
 import { TerminalProvider } from '../ui/contexts/TerminalContext.js';
+import {
+  OverflowProvider,
+  useOverflowActions,
+  useOverflowState,
+  type OverflowActions,
+  type OverflowState,
+} from '../ui/contexts/OverflowContext.js';
 
 import { makeFakeConfig, type Config } from '@google/gemini-cli-core';
 import { FakePersistentState } from './persistentStateFake.js';
@@ -335,6 +342,8 @@ export type RenderInstance = {
   lastFrame: (options?: { allowEmpty?: boolean }) => string;
   terminal: Terminal;
   waitUntilReady: () => Promise<void>;
+  capturedOverflowState: OverflowState | undefined;
+  capturedOverflowActions: OverflowActions | undefined;
 };
 
 const instances: InkInstance[] = [];
@@ -343,7 +352,10 @@ const instances: InkInstance[] = [];
 export const render = (
   tree: React.ReactElement,
   terminalWidth?: number,
-): RenderInstance => {
+): Omit<
+  RenderInstance,
+  'capturedOverflowState' | 'capturedOverflowActions'
+> => {
   const cols = terminalWidth ?? 100;
   // We use 1000 rows to avoid windows with incorrect snapshots if a correct
   // value was used (e.g. 40 rows). The alternatives to make things worse are
@@ -562,6 +574,16 @@ const mockUIActions: UIActions = {
   handleNewAgentsSelect: vi.fn(),
 };
 
+let capturedOverflowState: OverflowState | undefined;
+let capturedOverflowActions: OverflowActions | undefined;
+const ContextCapture: React.FC<{ children: React.ReactNode }> = ({
+  children,
+}) => {
+  capturedOverflowState = useOverflowState();
+  capturedOverflowActions = useOverflowActions();
+  return <>{children}</>;
+};
+
 export const renderWithProviders = (
   component: React.ReactElement,
   {
@@ -663,6 +685,9 @@ export const renderWithProviders = (
     .filter((item): item is HistoryItemToolGroup => item.type === 'tool_group')
     .flatMap((item) => item.tools);
 
+  capturedOverflowState = undefined;
+  capturedOverflowActions = undefined;
+
   const renderResult = render(
     <AppContext.Provider value={appState}>
       <ConfigContext.Provider value={config}>
@@ -675,6 +700,7 @@ export const renderWithProviders = (
                     value={finalUiState.streamingState}
                   >
                     <UIActionsContext.Provider value={finalUIActions}>
+                      <OverflowProvider>
                         <ToolActionsProvider
                           config={config}
                           toolCalls={allToolCalls}
@@ -690,6 +716,7 @@ export const renderWithProviders = (
                               >
                                 <TerminalProvider>
                                   <ScrollProvider>
+                                    <ContextCapture>
                                       <Box
                                         width={terminalWidth}
                                         flexShrink={0}
@@ -698,12 +725,14 @@ export const renderWithProviders = (
                                       >
                                         {component}
                                       </Box>
+                                    </ContextCapture>
                                   </ScrollProvider>
                                 </TerminalProvider>
                               </MouseProvider>
                             </KeypressProvider>
                           </AskUserActionsProvider>
                         </ToolActionsProvider>
+                      </OverflowProvider>
                     </UIActionsContext.Provider>
                   </StreamingContext.Provider>
                 </SessionStatsProvider>
@@ -718,6 +747,8 @@ export const renderWithProviders = (
 
   return {
     ...renderResult,
+    capturedOverflowState,
+    capturedOverflowActions,
     simulateClick: (col: number, row: number, button?: 0 | 1 | 2) =>
       simulateClick(renderResult.stdin, col, row, button),
   };

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

@@ -105,6 +105,11 @@ import {
   type UIActions,
 } from './contexts/UIActionsContext.js';
 import { KeypressProvider } from './contexts/KeypressContext.js';
+import { OverflowProvider } from './contexts/OverflowContext.js';
+import {
+  useOverflowActions,
+  type OverflowActions,
+} from './contexts/OverflowContext.js';
 
 // Mock useStdout to capture terminal title writes
 vi.mock('ink', async (importOriginal) => {
@@ -120,9 +125,11 @@ vi.mock('ink', async (importOriginal) => {
 // so we can assert against them in our tests.
 let capturedUIState: UIState;
 let capturedUIActions: UIActions;
+let capturedOverflowActions: OverflowActions;
 function TestContextConsumer() {
   capturedUIState = useContext(UIStateContext)!;
   capturedUIActions = useContext(UIActionsContext)!;
+  capturedOverflowActions = useOverflowActions()!;
   return null;
 }
 
@@ -229,7 +236,10 @@ import {
   disableMouseEvents,
 } from '@google/gemini-cli-core';
 import { type ExtensionManager } from '../config/extension-manager.js';
-import { WARNING_PROMPT_DURATION_MS } from './constants.js';
+import {
+  WARNING_PROMPT_DURATION_MS,
+  EXPAND_HINT_DURATION_MS,
+} from './constants.js';
 
 describe('AppContainer State Management', () => {
   let mockConfig: Config;
@@ -255,6 +265,7 @@ describe('AppContainer State Management', () => {
   } = {}) => (
     <SettingsContext.Provider value={settings}>
       <KeypressProvider config={config}>
+        <OverflowProvider>
           <AppContainer
             config={config}
             version={version}
@@ -262,6 +273,7 @@ describe('AppContainer State Management', () => {
             startupWarnings={startupWarnings}
             resumedSessionData={resumedSessionData}
           />
+        </OverflowProvider>
       </KeypressProvider>
     </SettingsContext.Provider>
   );
@@ -2687,12 +2699,14 @@ describe('AppContainer State Management', () => {
       const getTree = (settings: LoadedSettings) => (
         <SettingsContext.Provider value={settings}>
           <KeypressProvider config={mockConfig}>
+            <OverflowProvider>
               <AppContainer
                 config={mockConfig}
                 version="1.0.0"
                 initializationResult={mockInitResult}
               />
               <TestChild />
+            </OverflowProvider>
           </KeypressProvider>
         </SettingsContext.Provider>
       );
@@ -3303,6 +3317,306 @@ describe('AppContainer State Management', () => {
     });
   });
 
+  describe('Submission Handling', () => {
+    it('resets expansion state on submission when not in alternate buffer', async () => {
+      const { checkPermissions } = await import(
+        './hooks/atCommandProcessor.js'
+      );
+      vi.mocked(checkPermissions).mockResolvedValue([]);
+
+      let unmount: () => void;
+      await act(async () => {
+        unmount = renderAppContainer({
+          settings: {
+            ...mockSettings,
+            merged: {
+              ...mockSettings.merged,
+              ui: { ...mockSettings.merged.ui, useAlternateBuffer: false },
+            },
+          } as LoadedSettings,
+        }).unmount;
+      });
+
+      await waitFor(() => expect(capturedUIActions).toBeTruthy());
+
+      // Expand first
+      act(() => capturedUIActions.setConstrainHeight(false));
+      expect(capturedUIState.constrainHeight).toBe(false);
+
+      // Reset mock stdout to clear any initial writes
+      mocks.mockStdout.write.mockClear();
+
+      // Submit
+      await act(async () => capturedUIActions.handleFinalSubmit('test prompt'));
+
+      // Should be reset
+      expect(capturedUIState.constrainHeight).toBe(true);
+      // Should refresh static (which clears terminal in non-alternate buffer)
+      expect(mocks.mockStdout.write).toHaveBeenCalledWith(
+        ansiEscapes.clearTerminal,
+      );
+      unmount!();
+    });
+
+    it('resets expansion state on submission when in alternate buffer without clearing terminal', async () => {
+      const { checkPermissions } = await import(
+        './hooks/atCommandProcessor.js'
+      );
+      vi.mocked(checkPermissions).mockResolvedValue([]);
+
+      let unmount: () => void;
+      await act(async () => {
+        unmount = renderAppContainer({
+          settings: {
+            ...mockSettings,
+            merged: {
+              ...mockSettings.merged,
+              ui: { ...mockSettings.merged.ui, useAlternateBuffer: true },
+            },
+          } as LoadedSettings,
+        }).unmount;
+      });
+
+      await waitFor(() => expect(capturedUIActions).toBeTruthy());
+
+      // Expand first
+      act(() => capturedUIActions.setConstrainHeight(false));
+      expect(capturedUIState.constrainHeight).toBe(false);
+
+      // Reset mock stdout
+      mocks.mockStdout.write.mockClear();
+
+      // Submit
+      await act(async () => capturedUIActions.handleFinalSubmit('test prompt'));
+
+      // Should be reset
+      expect(capturedUIState.constrainHeight).toBe(true);
+      // Should NOT refresh static's clearTerminal in alternate buffer
+      expect(mocks.mockStdout.write).not.toHaveBeenCalledWith(
+        ansiEscapes.clearTerminal,
+      );
+      unmount!();
+    });
+  });
+
+  describe('Overflow Hint Handling', () => {
+    beforeEach(() => {
+      vi.useFakeTimers();
+    });
+
+    afterEach(() => {
+      vi.useRealTimers();
+    });
+
+    it('sets showIsExpandableHint when overflow occurs in Standard Mode and hides after 10s', async () => {
+      let unmount: () => void;
+      await act(async () => {
+        const result = renderAppContainer();
+        unmount = result.unmount;
+      });
+      await waitFor(() => expect(capturedUIState).toBeTruthy());
+
+      // Trigger overflow
+      act(() => {
+        capturedOverflowActions.addOverflowingId('test-id');
+      });
+
+      await waitFor(() => {
+        // Should show hint because we are in Standard Mode (default settings) and have overflow
+        expect(capturedUIState.showIsExpandableHint).toBe(true);
+      });
+
+      // Advance just before the timeout
+      act(() => {
+        vi.advanceTimersByTime(EXPAND_HINT_DURATION_MS - 100);
+      });
+      expect(capturedUIState.showIsExpandableHint).toBe(true);
+
+      // Advance to hit the timeout mark
+      act(() => {
+        vi.advanceTimersByTime(100);
+      });
+      await waitFor(() => {
+        expect(capturedUIState.showIsExpandableHint).toBe(false);
+      });
+
+      unmount!();
+    });
+
+    it('toggles expansion state and resets the hint timer when Ctrl+O is pressed in Standard Mode', async () => {
+      let unmount: () => void;
+      let stdin: ReturnType<typeof renderAppContainer>['stdin'];
+      await act(async () => {
+        const result = renderAppContainer();
+        unmount = result.unmount;
+        stdin = result.stdin;
+      });
+      await waitFor(() => expect(capturedUIState).toBeTruthy());
+
+      // Initial state is constrainHeight = true
+      expect(capturedUIState.constrainHeight).toBe(true);
+
+      // Trigger overflow so the hint starts showing
+      act(() => {
+        capturedOverflowActions.addOverflowingId('test-id');
+      });
+
+      await waitFor(() => {
+        expect(capturedUIState.showIsExpandableHint).toBe(true);
+      });
+
+      // Advance half the duration
+      act(() => {
+        vi.advanceTimersByTime(EXPAND_HINT_DURATION_MS / 2);
+      });
+      expect(capturedUIState.showIsExpandableHint).toBe(true);
+
+      // Simulate Ctrl+O
+      act(() => {
+        stdin.write('\x0f'); // \x0f is Ctrl+O
+      });
+
+      await waitFor(() => {
+        // constrainHeight should toggle
+        expect(capturedUIState.constrainHeight).toBe(false);
+      });
+
+      // Advance enough that the original timer would have expired if it hadn't reset
+      act(() => {
+        vi.advanceTimersByTime(EXPAND_HINT_DURATION_MS / 2 + 1000);
+      });
+
+      // We expect it to still be true because Ctrl+O should have reset the timer
+      expect(capturedUIState.showIsExpandableHint).toBe(true);
+
+      // Advance remaining time to reach the new timeout
+      act(() => {
+        vi.advanceTimersByTime(EXPAND_HINT_DURATION_MS / 2 - 1000);
+      });
+
+      await waitFor(() => {
+        expect(capturedUIState.showIsExpandableHint).toBe(false);
+      });
+
+      unmount!();
+    });
+
+    it('toggles Ctrl+O multiple times and verifies the hint disappears exactly after the last toggle', async () => {
+      let unmount: () => void;
+      let stdin: ReturnType<typeof renderAppContainer>['stdin'];
+      await act(async () => {
+        const result = renderAppContainer();
+        unmount = result.unmount;
+        stdin = result.stdin;
+      });
+      await waitFor(() => expect(capturedUIState).toBeTruthy());
+
+      // Initial state is constrainHeight = true
+      expect(capturedUIState.constrainHeight).toBe(true);
+
+      // Trigger overflow so the hint starts showing
+      act(() => {
+        capturedOverflowActions.addOverflowingId('test-id');
+      });
+
+      await waitFor(() => {
+        expect(capturedUIState.showIsExpandableHint).toBe(true);
+      });
+
+      // Advance half the duration
+      act(() => {
+        vi.advanceTimersByTime(EXPAND_HINT_DURATION_MS / 2);
+      });
+      expect(capturedUIState.showIsExpandableHint).toBe(true);
+
+      // First toggle 'on' (expanded)
+      act(() => {
+        stdin.write('\x0f'); // Ctrl+O
+      });
+      await waitFor(() => {
+        expect(capturedUIState.constrainHeight).toBe(false);
+      });
+
+      // Wait 1 second
+      act(() => {
+        vi.advanceTimersByTime(1000);
+      });
+      expect(capturedUIState.showIsExpandableHint).toBe(true);
+
+      // Second toggle 'off' (collapsed)
+      act(() => {
+        stdin.write('\x0f'); // Ctrl+O
+      });
+      await waitFor(() => {
+        expect(capturedUIState.constrainHeight).toBe(true);
+      });
+
+      // Wait 1 second
+      act(() => {
+        vi.advanceTimersByTime(1000);
+      });
+      expect(capturedUIState.showIsExpandableHint).toBe(true);
+
+      // Third toggle 'on' (expanded)
+      act(() => {
+        stdin.write('\x0f'); // Ctrl+O
+      });
+      await waitFor(() => {
+        expect(capturedUIState.constrainHeight).toBe(false);
+      });
+
+      // Now we wait just before the timeout from the LAST toggle.
+      // It should still be true.
+      act(() => {
+        vi.advanceTimersByTime(EXPAND_HINT_DURATION_MS - 100);
+      });
+      expect(capturedUIState.showIsExpandableHint).toBe(true);
+
+      // Wait 0.1s more to hit exactly the timeout since the last toggle.
+      // It should hide now.
+      act(() => {
+        vi.advanceTimersByTime(100);
+      });
+      await waitFor(() => {
+        expect(capturedUIState.showIsExpandableHint).toBe(false);
+      });
+
+      unmount!();
+    });
+
+    it('does NOT set showIsExpandableHint when overflow occurs in Alternate Buffer Mode', async () => {
+      const alternateSettings = mergeSettings({}, {}, {}, {}, true);
+      const settingsWithAlternateBuffer = {
+        merged: {
+          ...alternateSettings,
+          ui: {
+            ...alternateSettings.ui,
+            useAlternateBuffer: true,
+          },
+        },
+      } as unknown as LoadedSettings;
+
+      let unmount: () => void;
+      await act(async () => {
+        const result = renderAppContainer({
+          settings: settingsWithAlternateBuffer,
+        });
+        unmount = result.unmount;
+      });
+      await waitFor(() => expect(capturedUIState).toBeTruthy());
+
+      // Trigger overflow
+      act(() => {
+        capturedOverflowActions.addOverflowingId('test-id');
+      });
+
+      // Should NOT show hint because we are in Alternate Buffer Mode
+      expect(capturedUIState.showIsExpandableHint).toBe(false);
+
+      unmount!();
+    });
+  });
+
   describe('Permission Handling', () => {
     it('shows permission dialog when checkPermissions returns paths', async () => {
       const { checkPermissions } = await import(

packages/cli/src/ui/AppContainer.tsx

@@ -95,6 +95,10 @@ import { useSettingsCommand } from './hooks/useSettingsCommand.js';
 import { useModelCommand } from './hooks/useModelCommand.js';
 import { useSlashCommandProcessor } from './hooks/slashCommandProcessor.js';
 import { useVimMode } from './contexts/VimModeContext.js';
+import {
+  useOverflowActions,
+  useOverflowState,
+} from './contexts/OverflowContext.js';
 import { useConsoleMessages } from './hooks/useConsoleMessages.js';
 import { useTerminalSize } from './hooks/useTerminalSize.js';
 import { calculatePromptWidths } from './components/InputPrompt.js';
@@ -151,6 +155,7 @@ import { useBackgroundShellManager } from './hooks/useBackgroundShellManager.js'
 import {
   WARNING_PROMPT_DURATION_MS,
   QUEUE_ERROR_DISPLAY_DURATION_MS,
+  EXPAND_HINT_DURATION_MS,
 } from './constants.js';
 import { LoginWithGoogleRestartDialog } from './auth/LoginWithGoogleRestartDialog.js';
 import { NewAgentsChoice } from './components/NewAgentsNotification.js';
@@ -214,6 +219,7 @@ const SHELL_HEIGHT_PADDING = 10;
 export const AppContainer = (props: AppContainerProps) => {
   const { config, initializationResult, resumedSessionData } = props;
   const settings = useSettings();
+  const { reset } = useOverflowActions()!;
   const notificationsEnabled = isNotificationsEnabled(settings);
 
   const historyManager = useHistory({
@@ -262,6 +268,54 @@ export const AppContainer = (props: AppContainerProps) => {
   );
 
   const [newAgents, setNewAgents] = useState<AgentDefinition[] | null>(null);
+  const [constrainHeight, setConstrainHeight] = useState<boolean>(true);
+  const [showIsExpandableHint, setShowIsExpandableHint] = useState(false);
+  const expandHintTimerRef = useRef<NodeJS.Timeout | null>(null);
+  const overflowState = useOverflowState();
+  const overflowingIdsSize = overflowState?.overflowingIds.size ?? 0;
+  const hasOverflowState = overflowingIdsSize > 0 || !constrainHeight;
+
+  /**
+   * Manages the visibility and x-second timer for the expansion hint.
+   *
+   * This effect triggers the timer countdown whenever an overflow is detected
+   * or the user manually toggles the expansion state with Ctrl+O. We use a stable
+   * boolean dependency (hasOverflowState) to ensure the timer only resets on
+   * genuine state transitions, preventing it from infinitely resetting during
+   * active text streaming.
+   */
+  useEffect(() => {
+    if (isAlternateBuffer) {
+      setShowIsExpandableHint(false);
+      if (expandHintTimerRef.current) {
+        clearTimeout(expandHintTimerRef.current);
+      }
+      return;
+    }
+
+    if (hasOverflowState) {
+      setShowIsExpandableHint(true);
+      if (expandHintTimerRef.current) {
+        clearTimeout(expandHintTimerRef.current);
+      }
+      expandHintTimerRef.current = setTimeout(() => {
+        setShowIsExpandableHint(false);
+      }, EXPAND_HINT_DURATION_MS);
+    }
+  }, [hasOverflowState, isAlternateBuffer, constrainHeight]);
+
+  /**
+   * Safe cleanup to ensure the expansion hint timer is cancelled when the
+   * component unmounts, preventing memory leaks.
+   */
+  useEffect(
+    () => () => {
+      if (expandHintTimerRef.current) {
+        clearTimeout(expandHintTimerRef.current);
+      }
+    },
+    [],
+  );
 
   const [defaultBannerText, setDefaultBannerText] = useState('');
   const [warningBannerText, setWarningBannerText] = useState('');
@@ -1189,6 +1243,19 @@ Logging in with Google... Restarting Gemini CLI to continue.
 
   const handleFinalSubmit = useCallback(
     async (submittedValue: string) => {
+      reset();
+      // Explicitly hide the expansion hint and clear its x-second timer when a new turn begins.
+      setShowIsExpandableHint(false);
+      if (expandHintTimerRef.current) {
+        clearTimeout(expandHintTimerRef.current);
+      }
+      if (!constrainHeight) {
+        setConstrainHeight(true);
+        if (!isAlternateBuffer) {
+          refreshStatic();
+        }
+      }
+
       const isSlash = isSlashCommand(submittedValue.trim());
       const isIdle = streamingState === StreamingState.Idle;
       const isAgentRunning =
@@ -1247,15 +1314,32 @@ Logging in with Google... Restarting Gemini CLI to continue.
       pendingSlashCommandHistoryItems,
       pendingGeminiHistoryItems,
       config,
+      constrainHeight,
+      setConstrainHeight,
+      isAlternateBuffer,
+      refreshStatic,
+      reset,
       handleHintSubmit,
     ],
   );
 
   const handleClearScreen = useCallback(() => {
+    reset();
+    // Explicitly hide the expansion hint and clear its x-second timer when clearing the screen.
+    setShowIsExpandableHint(false);
+    if (expandHintTimerRef.current) {
+      clearTimeout(expandHintTimerRef.current);
+    }
     historyManager.clearItems();
     clearConsoleMessagesState();
     refreshStatic();
-  }, [historyManager, clearConsoleMessagesState, refreshStatic]);
+  }, [
+    historyManager,
+    clearConsoleMessagesState,
+    refreshStatic,
+    reset,
+    setShowIsExpandableHint,
+  ]);
 
   const { handleInput: vimHandleInput } = useVim(buffer, handleFinalSubmit);
 
@@ -1425,7 +1509,7 @@ Logging in with Google... Restarting Gemini CLI to continue.
       windowMs: WARNING_PROMPT_DURATION_MS,
       onRepeat: handleExitRepeat,
     });
-  const [constrainHeight, setConstrainHeight] = useState<boolean>(true);
+
   const [ideContextState, setIdeContextState] = useState<
     IdeContext | undefined
   >();
@@ -1655,6 +1739,19 @@ Logging in with Google... Restarting Gemini CLI to continue.
       if (!constrainHeight) {
         enteringConstrainHeightMode = true;
         setConstrainHeight(true);
+        if (keyMatchers[Command.SHOW_MORE_LINES](key)) {
+          // If the user manually collapses the view, show the hint and reset the x-second timer.
+          setShowIsExpandableHint(true);
+          if (expandHintTimerRef.current) {
+            clearTimeout(expandHintTimerRef.current);
+          }
+          expandHintTimerRef.current = setTimeout(() => {
+            setShowIsExpandableHint(false);
+          }, EXPAND_HINT_DURATION_MS);
+        }
+        if (!isAlternateBuffer) {
+          refreshStatic();
+        }
       }
 
       if (keyMatchers[Command.SHOW_ERROR_DETAILS](key)) {
@@ -1698,6 +1795,17 @@ Logging in with Google... Restarting Gemini CLI to continue.
         !enteringConstrainHeightMode
       ) {
         setConstrainHeight(false);
+        // If the user manually expands the view, show the hint and reset the x-second timer.
+        setShowIsExpandableHint(true);
+        if (expandHintTimerRef.current) {
+          clearTimeout(expandHintTimerRef.current);
+        }
+        expandHintTimerRef.current = setTimeout(() => {
+          setShowIsExpandableHint(false);
+        }, EXPAND_HINT_DURATION_MS);
+        if (!isAlternateBuffer) {
+          refreshStatic();
+        }
         return true;
       } else if (
         (keyMatchers[Command.FOCUS_SHELL_INPUT](key) ||
@@ -2218,6 +2326,7 @@ Logging in with Google... Restarting Gemini CLI to continue.
       isBackgroundShellListOpen,
       adminSettingsChanged,
       newAgents,
+      showIsExpandableHint,
       hintMode:
         config.isModelSteeringEnabled() &&
         isToolExecuting([
@@ -2344,6 +2453,7 @@ Logging in with Google... Restarting Gemini CLI to continue.
       backgroundShells,
       adminSettingsChanged,
       newAgents,
+      showIsExpandableHint,
     ],
   );
 

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

@@ -173,7 +173,9 @@ describe('FolderTrustDialog', () => {
     // Initial state: truncated
     await waitFor(() => {
       expect(lastFrame()).toContain('Do you trust the files in this folder?');
-      expect(lastFrame()).toContain('Press ctrl-o to show more lines');
+      // In standard terminal mode, the expansion hint is handled globally by ToastDisplay
+      // via AppContainer, so it should not be present in the dialog's local frame.
+      expect(lastFrame()).not.toContain('Press Ctrl+O');
       expect(lastFrame()).toContain('hidden');
     });
 

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

@@ -285,8 +285,7 @@ export const FolderTrustDialog: React.FC<FolderTrustDialogProps> = ({
     );
   };
 
-  return (
-    <OverflowProvider>
+  const content = (
     <Box flexDirection="column" width="100%">
       <Box flexDirection="column" marginLeft={1} marginRight={1}>
         {renderContent()}
@@ -312,6 +311,11 @@ export const FolderTrustDialog: React.FC<FolderTrustDialogProps> = ({
         </Box>
       )}
     </Box>
-    </OverflowProvider>
+  );
+
+  return isAlternateBuffer ? (
+    <OverflowProvider>{content}</OverflowProvider>
+  ) : (
+    content
   );
 };

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

@@ -46,6 +46,7 @@ interface HistoryItemDisplayProps {
   isPending: boolean;
   commands?: readonly SlashCommand[];
   availableTerminalHeightGemini?: number;
+  isExpandable?: boolean;
 }
 
 export const HistoryItemDisplay: React.FC<HistoryItemDisplayProps> = ({
@@ -55,6 +56,7 @@ export const HistoryItemDisplay: React.FC<HistoryItemDisplayProps> = ({
   isPending,
   commands,
   availableTerminalHeightGemini,
+  isExpandable,
 }) => {
   const settings = useSettings();
   const inlineThinkingMode = getInlineThinkingMode(settings);
@@ -180,6 +182,7 @@ export const HistoryItemDisplay: React.FC<HistoryItemDisplayProps> = ({
           terminalWidth={terminalWidth}
           borderTop={itemForDisplay.borderTop}
           borderBottom={itemForDisplay.borderBottom}
+          isExpandable={isExpandable}
         />
       )}
       {itemForDisplay.type === 'compression' && (

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

@@ -493,7 +493,8 @@ describe('MainContent', () => {
         isAlternateBuffer: true,
         embeddedShellFocused: true,
         constrainHeight: true,
-        shouldShowLine1: true,
+        shouldShowLine1: false,
+        staticAreaMaxItemHeight: 15,
       },
       {
         name: 'ASB mode - Unfocused shell',
@@ -501,6 +502,7 @@ describe('MainContent', () => {
         embeddedShellFocused: false,
         constrainHeight: true,
         shouldShowLine1: false,
+        staticAreaMaxItemHeight: 15,
       },
       {
         name: 'Normal mode - Constrained height',
@@ -508,13 +510,15 @@ describe('MainContent', () => {
         embeddedShellFocused: false,
         constrainHeight: true,
         shouldShowLine1: false,
+        staticAreaMaxItemHeight: 15,
       },
       {
         name: 'Normal mode - Unconstrained height',
         isAlternateBuffer: false,
         embeddedShellFocused: false,
         constrainHeight: false,
-        shouldShowLine1: false,
+        shouldShowLine1: true,
+        staticAreaMaxItemHeight: 15,
       },
     ];
 
@@ -525,6 +529,7 @@ describe('MainContent', () => {
         embeddedShellFocused,
         constrainHeight,
         shouldShowLine1,
+        staticAreaMaxItemHeight,
       }) => {
         vi.mocked(useAlternateBuffer).mockReturnValue(isAlternateBuffer);
         const ptyId = 123;
@@ -554,6 +559,7 @@ describe('MainContent', () => {
             },
           ],
           availableTerminalHeight: 30, // In ASB mode, focused shell should get ~28 lines
+          staticAreaMaxItemHeight,
           terminalHeight: 50,
           terminalWidth: 100,
           mainAreaWidth: 100,

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

@@ -47,32 +47,61 @@ export const MainContent = () => {
     pendingHistoryItems,
     mainAreaWidth,
     staticAreaMaxItemHeight,
-    availableTerminalHeight,
     cleanUiDetailsVisible,
   } = uiState;
   const showHeaderDetails = cleanUiDetailsVisible;
 
+  const lastUserPromptIndex = useMemo(() => {
+    for (let i = uiState.history.length - 1; i >= 0; i--) {
+      const type = uiState.history[i].type;
+      if (type === 'user' || type === 'user_shell') {
+        return i;
+      }
+    }
+    return -1;
+  }, [uiState.history]);
+
   const historyItems = useMemo(
     () =>
-      uiState.history.map((h) => (
+      uiState.history.map((h, index) => {
+        const isExpandable = index > lastUserPromptIndex;
+        return (
           <MemoizedHistoryItemDisplay
             terminalWidth={mainAreaWidth}
-          availableTerminalHeight={staticAreaMaxItemHeight}
+            availableTerminalHeight={
+              uiState.constrainHeight || !isExpandable
+                ? staticAreaMaxItemHeight
+                : undefined
+            }
             availableTerminalHeightGemini={MAX_GEMINI_MESSAGE_LINES}
             key={h.id}
             item={h}
             isPending={false}
             commands={uiState.slashCommands}
+            isExpandable={isExpandable}
           />
-      )),
+        );
+      }),
     [
       uiState.history,
       mainAreaWidth,
       staticAreaMaxItemHeight,
       uiState.slashCommands,
+      uiState.constrainHeight,
+      lastUserPromptIndex,
     ],
   );
 
+  const staticHistoryItems = useMemo(
+    () => historyItems.slice(0, lastUserPromptIndex + 1),
+    [historyItems, lastUserPromptIndex],
+  );
+
+  const lastResponseHistoryItems = useMemo(
+    () => historyItems.slice(lastUserPromptIndex + 1),
+    [historyItems, lastUserPromptIndex],
+  );
+
   const pendingItems = useMemo(
     () => (
       <Box flexDirection="column">
@@ -80,14 +109,12 @@ export const MainContent = () => {
           <HistoryItemDisplay
             key={i}
             availableTerminalHeight={
-              (uiState.constrainHeight && !isAlternateBuffer) ||
-              isAlternateBuffer
-                ? availableTerminalHeight
-                : undefined
+              uiState.constrainHeight ? staticAreaMaxItemHeight : undefined
             }
             terminalWidth={mainAreaWidth}
             item={{ ...item, id: 0 }}
             isPending={true}
+            isExpandable={true}
           />
         ))}
         {showConfirmationQueue && confirmingTool && (
@@ -98,8 +125,7 @@ export const MainContent = () => {
     [
       pendingHistoryItems,
       uiState.constrainHeight,
-      isAlternateBuffer,
-      availableTerminalHeight,
+      staticAreaMaxItemHeight,
       mainAreaWidth,
       showConfirmationQueue,
       confirmingTool,
@@ -109,10 +135,14 @@ export const MainContent = () => {
   const virtualizedData = useMemo(
     () => [
       { type: 'header' as const },
-      ...uiState.history.map((item) => ({ type: 'history' as const, item })),
+      ...uiState.history.map((item, index) => ({
+        type: 'history' as const,
+        item,
+        isExpandable: index > lastUserPromptIndex,
+      })),
       { type: 'pending' as const },
     ],
-    [uiState.history],
+    [uiState.history, lastUserPromptIndex],
   );
 
   const renderItem = useCallback(
@@ -129,12 +159,17 @@ export const MainContent = () => {
         return (
           <MemoizedHistoryItemDisplay
             terminalWidth={mainAreaWidth}
-            availableTerminalHeight={undefined}
+            availableTerminalHeight={
+              uiState.constrainHeight || !item.isExpandable
+                ? staticAreaMaxItemHeight
+                : undefined
+            }
             availableTerminalHeightGemini={MAX_GEMINI_MESSAGE_LINES}
             key={item.item.id}
             item={item.item}
             isPending={false}
             commands={uiState.slashCommands}
+            isExpandable={item.isExpandable}
           />
         );
       } else {
@@ -147,6 +182,8 @@ export const MainContent = () => {
       mainAreaWidth,
       uiState.slashCommands,
       pendingItems,
+      uiState.constrainHeight,
+      staticAreaMaxItemHeight,
     ],
   );
 
@@ -176,7 +213,8 @@ export const MainContent = () => {
         key={uiState.historyRemountKey}
         items={[
           <AppHeader key="app-header" version={version} />,
-          ...historyItems,
+          ...staticHistoryItems,
+          ...lastResponseHistoryItems,
         ]}
       >
         {(item) => item}

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

@@ -29,7 +29,6 @@ describe('ShowMoreLines', () => {
   it.each([
     [new Set(), StreamingState.Idle, true], // No overflow
     [new Set(['1']), StreamingState.Idle, false], // Not constraining height
-    [new Set(['1']), StreamingState.Responding, true], // Streaming
   ])(
     'renders nothing when: overflow=%s, streaming=%s, constrain=%s',
     async (overflowingIds, streamingState, constrainHeight) => {
@@ -46,9 +45,28 @@ describe('ShowMoreLines', () => {
     },
   );
 
-  it.each([[StreamingState.Idle], [StreamingState.WaitingForConfirmation]])(
-    'renders message when overflowing and state is %s',
+  it('renders nothing in STANDARD mode even if overflowing', async () => {
+    mockUseAlternateBuffer.mockReturnValue(false);
+    mockUseOverflowState.mockReturnValue({
+      overflowingIds: new Set(['1']),
+    } as NonNullable<ReturnType<typeof useOverflowState>>);
+    mockUseStreamingContext.mockReturnValue(StreamingState.Idle);
+    const { lastFrame, waitUntilReady, unmount } = render(
+      <ShowMoreLines constrainHeight={true} />,
+    );
+    await waitUntilReady();
+    expect(lastFrame({ allowEmpty: true })).toBe('');
+    unmount();
+  });
+
+  it.each([
+    [StreamingState.Idle],
+    [StreamingState.WaitingForConfirmation],
+    [StreamingState.Responding],
+  ])(
+    'renders message in ASB mode when overflowing and state is %s',
     async (streamingState) => {
+      mockUseAlternateBuffer.mockReturnValue(true);
       mockUseOverflowState.mockReturnValue({
         overflowingIds: new Set(['1']),
       } as NonNullable<ReturnType<typeof useOverflowState>>);
@@ -57,8 +75,39 @@ describe('ShowMoreLines', () => {
         <ShowMoreLines constrainHeight={true} />,
       );
       await waitUntilReady();
-      expect(lastFrame()).toContain('Press ctrl-o to show more lines');
+      expect(lastFrame().toLowerCase()).toContain(
+        'press ctrl+o to show more lines',
+      );
       unmount();
     },
   );
+
+  it('renders message in ASB mode when isOverflowing prop is true even if internal overflow state is empty', async () => {
+    mockUseAlternateBuffer.mockReturnValue(true);
+    mockUseOverflowState.mockReturnValue({
+      overflowingIds: new Set(),
+    } as NonNullable<ReturnType<typeof useOverflowState>>);
+    mockUseStreamingContext.mockReturnValue(StreamingState.Idle);
+    const { lastFrame, waitUntilReady, unmount } = render(
+      <ShowMoreLines constrainHeight={true} isOverflowing={true} />,
+    );
+    await waitUntilReady();
+    expect(lastFrame().toLowerCase()).toContain(
+      'press ctrl+o to show more lines',
+    );
+    unmount();
+  });
+
+  it('renders nothing when isOverflowing prop is false even if internal overflow state has IDs', async () => {
+    mockUseOverflowState.mockReturnValue({
+      overflowingIds: new Set(['1']),
+    } as NonNullable<ReturnType<typeof useOverflowState>>);
+    mockUseStreamingContext.mockReturnValue(StreamingState.Idle);
+    const { lastFrame, waitUntilReady, unmount } = render(
+      <ShowMoreLines constrainHeight={true} isOverflowing={false} />,
+    );
+    await waitUntilReady();
+    expect(lastFrame({ allowEmpty: true })).toBe('');
+    unmount();
+  });
 });

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

@@ -9,31 +9,42 @@ import { useOverflowState } from '../contexts/OverflowContext.js';
 import { useStreamingContext } from '../contexts/StreamingContext.js';
 import { StreamingState } from '../types.js';
 import { theme } from '../semantic-colors.js';
+import { useAlternateBuffer } from '../hooks/useAlternateBuffer.js';
 
 interface ShowMoreLinesProps {
   constrainHeight: boolean;
+  isOverflowing?: boolean;
 }
 
-export const ShowMoreLines = ({ constrainHeight }: ShowMoreLinesProps) => {
+export const ShowMoreLines = ({
+  constrainHeight,
+  isOverflowing: isOverflowingProp,
+}: ShowMoreLinesProps) => {
+  const isAlternateBuffer = useAlternateBuffer();
   const overflowState = useOverflowState();
   const streamingState = useStreamingContext();
 
+  const isOverflowing =
+    isOverflowingProp ??
+    (overflowState !== undefined && overflowState.overflowingIds.size > 0);
+
   if (
-    overflowState === undefined ||
-    overflowState.overflowingIds.size === 0 ||
+    !isAlternateBuffer ||
+    !isOverflowing ||
     !constrainHeight ||
     !(
       streamingState === StreamingState.Idle ||
-      streamingState === StreamingState.WaitingForConfirmation
+      streamingState === StreamingState.WaitingForConfirmation ||
+      streamingState === StreamingState.Responding
     )
   ) {
     return null;
   }
 
   return (
-    <Box paddingX={1}>
-      <Text color={theme.text.secondary} wrap="truncate">
-        Press ctrl-o to show more lines
+    <Box paddingX={1} marginBottom={1}>
+      <Text color={theme.text.accent} wrap="truncate">
+        Press Ctrl+O to show more lines
       </Text>
     </Box>
   );

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

@@ -35,12 +35,22 @@ describe('ToastDisplay', () => {
       buffer: { text: '' } as TextBuffer,
       history: [] as HistoryItem[],
       queueErrorMessage: null,
+      showIsExpandableHint: false,
     };
 
     it('returns false for default state', () => {
       expect(shouldShowToast(baseState as UIState)).toBe(false);
     });
 
+    it('returns true when showIsExpandableHint is true', () => {
+      expect(
+        shouldShowToast({
+          ...baseState,
+          showIsExpandableHint: true,
+        } as UIState),
+      ).toBe(true);
+    });
+
     it('returns true when ctrlCPressedOnce is true', () => {
       expect(
         shouldShowToast({ ...baseState, ctrlCPressedOnce: true } as UIState),
@@ -170,4 +180,22 @@ describe('ToastDisplay', () => {
     await waitUntilReady();
     expect(lastFrame()).toMatchSnapshot();
   });
+
+  it('renders expansion hint when showIsExpandableHint is true', async () => {
+    const { lastFrame, waitUntilReady } = renderToastDisplay({
+      showIsExpandableHint: true,
+      constrainHeight: true,
+    });
+    await waitUntilReady();
+    expect(lastFrame()).toContain('Press Ctrl+O to show more lines');
+  });
+
+  it('renders collapse hint when showIsExpandableHint is true and constrainHeight is false', async () => {
+    const { lastFrame, waitUntilReady } = renderToastDisplay({
+      showIsExpandableHint: true,
+      constrainHeight: false,
+    });
+    await waitUntilReady();
+    expect(lastFrame()).toContain('Press Ctrl+O to collapse lines');
+  });
 });

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

@@ -17,7 +17,8 @@ export function shouldShowToast(uiState: UIState): boolean {
     uiState.ctrlDPressedOnce ||
     (uiState.showEscapePrompt &&
       (uiState.buffer.text.length > 0 || uiState.history.length > 0)) ||
-    Boolean(uiState.queueErrorMessage)
+    Boolean(uiState.queueErrorMessage) ||
+    uiState.showIsExpandableHint
   );
 }
 
@@ -73,5 +74,14 @@ export const ToastDisplay: React.FC = () => {
     return <Text color={theme.status.error}>{uiState.queueErrorMessage}</Text>;
   }
 
+  if (uiState.showIsExpandableHint) {
+    const action = uiState.constrainHeight ? 'show more' : 'collapse';
+    return (
+      <Text color={theme.text.accent}>
+        Press Ctrl+O to {action} lines for the most recent response
+      </Text>
+    );
+  }
+
   return null;
 };

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

@@ -161,7 +161,7 @@ describe('ToolConfirmationQueue', () => {
       </Box>,
       {
         config: mockConfig,
-        useAlternateBuffer: false,
+        useAlternateBuffer: true,
         uiState: {
           terminalWidth: 80,
           terminalHeight: 20,
@@ -173,10 +173,11 @@ describe('ToolConfirmationQueue', () => {
     await waitUntilReady();
 
     await waitFor(() =>
-      expect(lastFrame()).toContain('Press ctrl-o to show more lines'),
+      expect(lastFrame()?.toLowerCase()).toContain(
+        'press ctrl+o to show more lines',
+      ),
     );
     expect(lastFrame()).toMatchSnapshot();
-    expect(lastFrame()).toContain('Press ctrl-o to show more lines');
     unmount();
   });
 
@@ -324,7 +325,7 @@ describe('ToolConfirmationQueue', () => {
     await waitUntilReady();
 
     const output = lastFrame();
-    expect(output).not.toContain('Press ctrl-o to show more lines');
+    expect(output).not.toContain('Press CTRL-O to show more lines');
     expect(output).toMatchSnapshot();
     unmount();
   });

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

@@ -71,13 +71,12 @@ export const ToolConfirmationQueue: React.FC<ToolConfirmationQueueProps> = ({
   // - 2 lines for the rounded border
   // - 2 lines for the Header (text + margin)
   // - 2 lines for Tool Identity (text + margin)
-  const availableContentHeight =
-    constrainHeight && !isAlternateBuffer
+  const availableContentHeight = constrainHeight
     ? Math.max(maxHeight - (hideToolIdentity ? 4 : 6), 4)
     : undefined;
 
-  return (
-    <OverflowProvider>
+  const content = (
+    <>
       <Box flexDirection="column" width={mainAreaWidth} flexShrink={0}>
         <StickyHeader
           width={mainAreaWidth}
@@ -152,6 +151,13 @@ export const ToolConfirmationQueue: React.FC<ToolConfirmationQueueProps> = ({
         />
       </Box>
       <ShowMoreLines constrainHeight={constrainHeight} />
-    </OverflowProvider>
+    </>
+  );
+
+  return isAlternateBuffer ? (
+    /* Shadow the global provider to maintain isolation in ASB mode. */
+    <OverflowProvider>{content}</OverflowProvider>
+  ) : (
+    content
   );
 };

packages/cli/src/ui/components/__snapshots__/AlternateBufferQuittingDisplay.test.tsx.snap

@@ -43,7 +43,6 @@ Tips for getting started:
 │ ✓  tool1 Description for tool 1                                          │
 │                                                                          │
 ╰──────────────────────────────────────────────────────────────────────────╯
-
 ╭──────────────────────────────────────────────────────────────────────────╮
 │ ✓  tool2 Description for tool 2                                          │
 │                                                                          │
@@ -90,7 +89,6 @@ Tips for getting started:
 │ ✓  tool1 Description for tool 1                                          │
 │                                                                          │
 ╰──────────────────────────────────────────────────────────────────────────╯
-
 ╭──────────────────────────────────────────────────────────────────────────╮
 │ ✓  tool2 Description for tool 2                                          │
 │                                                                          │

packages/cli/src/ui/components/__snapshots__/ConfigInitDisplay.test.tsx.snap

@@ -18,20 +18,8 @@ Spinner Connecting to MCP servers... (0/5) - Waiting for: s1, s2, s3, +2 more
 "
 `;
 
-exports[`ConfigInitDisplay > truncates list of waiting servers if too many 2`] = `
-"
-Spinner Connecting to MCP servers... (0/5) - Waiting for: s1, s2, s3, +2 more
-"
-`;
-
 exports[`ConfigInitDisplay > updates message on McpClientUpdate event 1`] = `
 "
 Spinner Connecting to MCP servers... (1/2) - Waiting for: server2
 "
 `;
-
-exports[`ConfigInitDisplay > updates message on McpClientUpdate event 2`] = `
-"
-Spinner Connecting to MCP servers... (1/2) - Waiting for: server2
-"
-`;

packages/cli/src/ui/components/__snapshots__/ExitPlanModeDialog.test.tsx.snap

@@ -27,33 +27,6 @@ Enter to select · ↑/↓ to navigate · Esc to cancel
 "
 `;
 
-exports[`ExitPlanModeDialog > useAlternateBuffer: false > bubbles up Ctrl+C when feedback is empty while editing 2`] = `
-"Overview
-
-Add user authentication to the CLI application.
-
-Implementation Steps
-
- 1. Create src/auth/AuthService.ts with login/logout methods
- 2. Add session storage in src/storage/SessionStore.ts
- 3. Update src/commands/index.ts to check auth status
- 4. Add tests in src/auth/__tests__/
-
-Files to Modify
-
- - src/index.ts - Add auth middleware
- - src/config.ts - Add auth configuration options
-
-  1.  Yes, automatically accept edits
-      Approves plan and allows tools to run automatically
-  2.  Yes, manually accept edits
-      Approves plan but requires confirmation for each tool
-● 3.  Type your feedback...
-
-Enter to submit · Esc to cancel
-"
-`;
-
 exports[`ExitPlanModeDialog > useAlternateBuffer: false > calls onFeedback when feedback is typed and submitted 1`] = `
 "Overview
 
@@ -81,33 +54,6 @@ Enter to select · ↑/↓ to navigate · Esc to cancel
 "
 `;
 
-exports[`ExitPlanModeDialog > useAlternateBuffer: false > calls onFeedback when feedback is typed and submitted 2`] = `
-"Overview
-
-Add user authentication to the CLI application.
-
-Implementation Steps
-
- 1. Create src/auth/AuthService.ts with login/logout methods
- 2. Add session storage in src/storage/SessionStore.ts
- 3. Update src/commands/index.ts to check auth status
- 4. Add tests in src/auth/__tests__/
-
-Files to Modify
-
- - src/index.ts - Add auth middleware
- - src/config.ts - Add auth configuration options
-
-  1.  Yes, automatically accept edits
-      Approves plan and allows tools to run automatically
-  2.  Yes, manually accept edits
-      Approves plan but requires confirmation for each tool
-● 3.  Add tests
-
-Enter to submit · Esc to cancel
-"
-`;
-
 exports[`ExitPlanModeDialog > useAlternateBuffer: false > displays error state when file read fails 1`] = `
 " Error reading plan: File not found
 "
@@ -194,33 +140,6 @@ Enter to select · ↑/↓ to navigate · Esc to cancel
 "
 `;
 
-exports[`ExitPlanModeDialog > useAlternateBuffer: true > bubbles up Ctrl+C when feedback is empty while editing 2`] = `
-"Overview
-
-Add user authentication to the CLI application.
-
-Implementation Steps
-
- 1. Create src/auth/AuthService.ts with login/logout methods
- 2. Add session storage in src/storage/SessionStore.ts
- 3. Update src/commands/index.ts to check auth status
- 4. Add tests in src/auth/__tests__/
-
-Files to Modify
-
- - src/index.ts - Add auth middleware
- - src/config.ts - Add auth configuration options
-
-  1.  Yes, automatically accept edits
-      Approves plan and allows tools to run automatically
-  2.  Yes, manually accept edits
-      Approves plan but requires confirmation for each tool
-● 3.  Type your feedback...
-
-Enter to submit · Esc to cancel
-"
-`;
-
 exports[`ExitPlanModeDialog > useAlternateBuffer: true > calls onFeedback when feedback is typed and submitted 1`] = `
 "Overview
 
@@ -248,33 +167,6 @@ Enter to select · ↑/↓ to navigate · Esc to cancel
 "
 `;
 
-exports[`ExitPlanModeDialog > useAlternateBuffer: true > calls onFeedback when feedback is typed and submitted 2`] = `
-"Overview
-
-Add user authentication to the CLI application.
-
-Implementation Steps
-
- 1. Create src/auth/AuthService.ts with login/logout methods
- 2. Add session storage in src/storage/SessionStore.ts
- 3. Update src/commands/index.ts to check auth status
- 4. Add tests in src/auth/__tests__/
-
-Files to Modify
-
- - src/index.ts - Add auth middleware
- - src/config.ts - Add auth configuration options
-
-  1.  Yes, automatically accept edits
-      Approves plan and allows tools to run automatically
-  2.  Yes, manually accept edits
-      Approves plan but requires confirmation for each tool
-● 3.  Add tests
-
-Enter to submit · Esc to cancel
-"
-`;
-
 exports[`ExitPlanModeDialog > useAlternateBuffer: true > displays error state when file read fails 1`] = `
 " Error reading plan: File not found
 "

packages/cli/src/ui/components/__snapshots__/MainContent.test.tsx.snap

@@ -6,27 +6,17 @@ AppHeader(full)
 ╭──────────────────────────────────────────────────────────────────────────────────────────────╮
 │ ⊷  Shell Command Running a long command...                                                   │
 │                                                                                              │
-│ Line 1                                                                                       │
-│ Line 2                                                                                       │
-│ Line 3                                                                                       │
-│ Line 4                                                                                       │
-│ Line 5                                                                                       │
-│ Line 6                                                                                       │
-│ Line 7                                                                                       │
-│ Line 8                                                                                       │
-│ Line 9                                                                                       │
 │ Line 10                                                                                      │
 │ Line 11                                                                                      │
 │ Line 12                                                                                      │
 │ Line 13                                                                                      │
 │ Line 14                                                                                      │
-│ Line 15                                                                                      │
-│ Line 16                                                                                      │
-│ Line 17                                                                                      │
-│ Line 18                                                                                      │
-│ Line 19                                                                                      │
-│ Line 20                                                                                      │
-│                                                                                              │
+│ Line 15                                                                                    █ │
+│ Line 16                                                                                    █ │
+│ Line 17                                                                                    █ │
+│ Line 18                                                                                    █ │
+│ Line 19                                                                                    █ │
+│ Line 20                                                                                    █ │
 ╰──────────────────────────────────────────────────────────────────────────────────────────────╯
 ShowMoreLines
 "
@@ -38,15 +28,11 @@ AppHeader(full)
 ╭──────────────────────────────────────────────────────────────────────────────────────────────╮
 │ ⊷  Shell Command Running a long command...                                                   │
 │                                                                                              │
-│ Line 6                                                                                       │
-│ Line 7                                                                                       │
-│ Line 8                                                                                       │
-│ Line 9                                                                                     ▄ │
-│ Line 10                                                                                    █ │
-│ Line 11                                                                                    █ │
-│ Line 12                                                                                    █ │
-│ Line 13                                                                                    █ │
-│ Line 14                                                                                    █ │
+│ Line 10                                                                                      │
+│ Line 11                                                                                      │
+│ Line 12                                                                                      │
+│ Line 13                                                                                      │
+│ Line 14                                                                                      │
 │ Line 15                                                                                    █ │
 │ Line 16                                                                                    █ │
 │ Line 17                                                                                    █ │
@@ -63,12 +49,7 @@ exports[`MainContent > MainContent Tool Output Height Logic > 'Normal mode - Con
 ╭──────────────────────────────────────────────────────────────────────────────────────────────╮
 │ ⊷  Shell Command Running a long command...                                                   │
 │                                                                                              │
-│ Line 6                                                                                       │
-│ Line 7                                                                                       │
-│ Line 8                                                                                       │
-│ Line 9                                                                                       │
-│ Line 10                                                                                      │
-│ Line 11                                                                                      │
+│ ... first 11 lines hidden ...                                                                │
 │ Line 12                                                                                      │
 │ Line 13                                                                                      │
 │ Line 14                                                                                      │
@@ -88,6 +69,11 @@ exports[`MainContent > MainContent Tool Output Height Logic > 'Normal mode - Unc
 ╭──────────────────────────────────────────────────────────────────────────────────────────────╮
 │ ⊷  Shell Command Running a long command...                                                   │
 │                                                                                              │
+│ Line 1                                                                                       │
+│ Line 2                                                                                       │
+│ Line 3                                                                                       │
+│ Line 4                                                                                       │
+│ Line 5                                                                                       │
 │ Line 6                                                                                       │
 │ Line 7                                                                                       │
 │ Line 8                                                                                       │

packages/cli/src/ui/components/__snapshots__/ToolConfirmationQueue.test.tsx.snap

@@ -16,7 +16,6 @@ exports[`ToolConfirmationQueue > calculates availableContentHeight based on avai
 │   4. No, suggest changes (esc)                                               │
 │                                                                              │
 ╰──────────────────────────────────────────────────────────────────────────────╯
- Press ctrl-o to show more lines
 "
 `;
 
@@ -107,7 +106,7 @@ exports[`ToolConfirmationQueue > renders expansion hint when content is long and
 │   4. No, suggest changes (esc)                                               │
 │                                                                              │
 ╰──────────────────────────────────────────────────────────────────────────────╯
- Press ctrl-o to show more lines
+ Press Ctrl+O to show more lines
 "
 `;
 

packages/cli/src/ui/components/messages/GeminiMessage.tsx

@@ -12,6 +12,7 @@ import { theme } from '../../semantic-colors.js';
 import { SCREEN_READER_MODEL_PREFIX } from '../../textConstants.js';
 import { useUIState } from '../../contexts/UIStateContext.js';
 import { useAlternateBuffer } from '../../hooks/useAlternateBuffer.js';
+import { OverflowProvider } from '../../contexts/OverflowContext.js';
 
 interface GeminiMessageProps {
   text: string;
@@ -31,7 +32,7 @@ export const GeminiMessage: React.FC<GeminiMessageProps> = ({
   const prefixWidth = prefix.length;
 
   const isAlternateBuffer = useAlternateBuffer();
-  return (
+  const content = (
     <Box flexDirection="row">
       <Box width={prefixWidth}>
         <Text color={theme.text.accent} aria-label={SCREEN_READER_MODEL_PREFIX}>
@@ -61,4 +62,11 @@ export const GeminiMessage: React.FC<GeminiMessageProps> = ({
       </Box>
     </Box>
   );
+
+  return isAlternateBuffer ? (
+    /* Shadow the global provider to maintain isolation in ASB mode. */
+    <OverflowProvider>{content}</OverflowProvider>
+  ) : (
+    content
+  );
 };

packages/cli/src/ui/components/messages/ShellToolMessage.test.tsx

@@ -191,7 +191,7 @@ describe('<ShellToolMessage />', () => {
         true,
       ],
       [
-        'defaults to ACTIVE_SHELL_MAX_LINES when availableTerminalHeight is undefined',
+        'defaults to ACTIVE_SHELL_MAX_LINES in alternate buffer when availableTerminalHeight is undefined',
         undefined,
         ACTIVE_SHELL_MAX_LINES,
         false,
@@ -219,5 +219,75 @@ describe('<ShellToolMessage />', () => {
       expect(frame.match(/Line \d+/g)?.length).toBe(expectedMaxLines);
       expect(frame).toMatchSnapshot();
     });
+
+    it('fully expands in standard mode when availableTerminalHeight is undefined', async () => {
+      const { lastFrame } = renderShell(
+        {
+          resultDisplay: LONG_OUTPUT,
+          renderOutputAsMarkdown: false,
+          availableTerminalHeight: undefined,
+          status: CoreToolCallStatus.Executing,
+        },
+        { useAlternateBuffer: false },
+      );
+
+      await waitFor(() => {
+        const frame = lastFrame();
+        // Should show all 100 lines
+        expect(frame.match(/Line \d+/g)?.length).toBe(100);
+      });
+    });
+
+    it('fully expands in alternate buffer mode when constrainHeight is false and isExpandable is true', async () => {
+      const { lastFrame, waitUntilReady } = renderShell(
+        {
+          resultDisplay: LONG_OUTPUT,
+          renderOutputAsMarkdown: false,
+          availableTerminalHeight: undefined,
+          status: CoreToolCallStatus.Success,
+          isExpandable: true,
+        },
+        {
+          useAlternateBuffer: true,
+          uiState: {
+            constrainHeight: false,
+          },
+        },
+      );
+
+      await waitUntilReady();
+      await waitFor(() => {
+        const frame = lastFrame();
+        // Should show all 100 lines because constrainHeight is false and isExpandable is true
+        expect(frame.match(/Line \d+/g)?.length).toBe(100);
+      });
+      expect(lastFrame()).toMatchSnapshot();
+    });
+
+    it('stays constrained in alternate buffer mode when isExpandable is false even if constrainHeight is false', async () => {
+      const { lastFrame, waitUntilReady } = renderShell(
+        {
+          resultDisplay: LONG_OUTPUT,
+          renderOutputAsMarkdown: false,
+          availableTerminalHeight: undefined,
+          status: CoreToolCallStatus.Success,
+          isExpandable: false,
+        },
+        {
+          useAlternateBuffer: true,
+          uiState: {
+            constrainHeight: false,
+          },
+        },
+      );
+
+      await waitUntilReady();
+      await waitFor(() => {
+        const frame = lastFrame();
+        // Should still be constrained to ACTIVE_SHELL_MAX_LINES (15) because isExpandable is false
+        expect(frame.match(/Line \d+/g)?.length).toBe(15);
+      });
+      expect(lastFrame()).toMatchSnapshot();
+    });
   });
 });

packages/cli/src/ui/components/messages/ShellToolMessage.tsx

@@ -15,24 +15,21 @@ import {
   ToolStatusIndicator,
   ToolInfo,
   TrailingIndicator,
-  STATUS_INDICATOR_WIDTH,
   isThisShellFocusable as checkIsShellFocusable,
   isThisShellFocused as checkIsShellFocused,
   useFocusHint,
   FocusHint,
 } from './ToolShared.js';
 import type { ToolMessageProps } from './ToolMessage.js';
-import {
-  ACTIVE_SHELL_MAX_LINES,
-  COMPLETED_SHELL_MAX_LINES,
-} from '../../constants.js';
+import { ACTIVE_SHELL_MAX_LINES } from '../../constants.js';
 import { useAlternateBuffer } from '../../hooks/useAlternateBuffer.js';
-import { type Config, CoreToolCallStatus } from '@google/gemini-cli-core';
-
 import { useUIState } from '../../contexts/UIStateContext.js';
+import { type Config } from '@google/gemini-cli-core';
+import { calculateShellMaxLines } from '../../utils/toolLayoutUtils.js';
 
 export interface ShellToolMessageProps extends ToolMessageProps {
   config?: Config;
+  isExpandable?: boolean;
 }
 
 export const ShellToolMessage: React.FC<ShellToolMessageProps> = ({
@@ -61,9 +58,15 @@ export const ShellToolMessage: React.FC<ShellToolMessageProps> = ({
   borderColor,
 
   borderDimColor,
+  isExpandable,
 }) => {
-  const { activePtyId: activeShellPtyId, embeddedShellFocused } = useUIState();
+  const {
+    activePtyId: activeShellPtyId,
+    embeddedShellFocused,
+    constrainHeight,
+  } = useUIState();
   const isAlternateBuffer = useAlternateBuffer();
+
   const isThisShellFocused = checkIsShellFocused(
     name,
     status,
@@ -155,59 +158,23 @@ export const ShellToolMessage: React.FC<ShellToolMessageProps> = ({
           terminalWidth={terminalWidth}
           renderOutputAsMarkdown={renderOutputAsMarkdown}
           hasFocus={isThisShellFocused}
-          maxLines={getShellMaxLines(
+          maxLines={calculateShellMaxLines({
             status,
             isAlternateBuffer,
             isThisShellFocused,
             availableTerminalHeight,
-          )}
+            constrainHeight,
+            isExpandable,
+          })}
         />
         {isThisShellFocused && config && (
-          <Box paddingLeft={STATUS_INDICATOR_WIDTH} marginTop={1}>
           <ShellInputPrompt
             activeShellPtyId={activeShellPtyId ?? null}
             focus={embeddedShellFocused}
             scrollPageSize={availableTerminalHeight ?? ACTIVE_SHELL_MAX_LINES}
           />
-          </Box>
         )}
       </Box>
     </>
   );
 };
-
-/**
- * Calculates the maximum number of lines to display for shell output.
- *
- * For completed processes (Success, Error, Canceled), it returns COMPLETED_SHELL_MAX_LINES.
- * For active processes, it returns the available terminal height if in alternate buffer mode
- * and focused. Otherwise, it returns ACTIVE_SHELL_MAX_LINES.
- *
- * This function ensures a finite number of lines is always returned to prevent performance issues.
- */
-function getShellMaxLines(
-  status: CoreToolCallStatus,
-  isAlternateBuffer: boolean,
-  isThisShellFocused: boolean,
-  availableTerminalHeight: number | undefined,
-): number {
-  if (
-    status === CoreToolCallStatus.Success ||
-    status === CoreToolCallStatus.Error ||
-    status === CoreToolCallStatus.Cancelled
-  ) {
-    return COMPLETED_SHELL_MAX_LINES;
-  }
-
-  if (availableTerminalHeight === undefined) {
-    return ACTIVE_SHELL_MAX_LINES;
-  }
-
-  const maxLinesBasedOnHeight = Math.max(1, availableTerminalHeight - 2);
-
-  if (isAlternateBuffer && isThisShellFocused) {
-    return maxLinesBasedOnHeight;
-  }
-
-  return Math.min(maxLinesBasedOnHeight, ACTIVE_SHELL_MAX_LINES);
-}

packages/cli/src/ui/components/messages/ToolGroupMessage.test.tsx

@@ -6,6 +6,7 @@
 
 import { renderWithProviders } from '../../../test-utils/render.js';
 import { describe, it, expect, vi, afterEach } from 'vitest';
+import { act } from 'react';
 import { ToolGroupMessage } from './ToolGroupMessage.js';
 import type {
   HistoryItem,
@@ -678,4 +679,194 @@ describe('<ToolGroupMessage />', () => {
       },
     );
   });
+
+  describe('Manual Overflow Detection', () => {
+    it('detects overflow for string results exceeding available height', async () => {
+      const toolCalls = [
+        createToolCall({
+          resultDisplay: 'line 1\nline 2\nline 3\nline 4\nline 5',
+        }),
+      ];
+      const { lastFrame, unmount, waitUntilReady } = renderWithProviders(
+        <ToolGroupMessage
+          {...baseProps}
+          item={{ id: 1, type: 'tool_group', tools: toolCalls }}
+          toolCalls={toolCalls}
+          availableTerminalHeight={6} // Very small height
+          isExpandable={true}
+        />,
+        {
+          config: baseMockConfig,
+          useAlternateBuffer: true,
+          uiState: {
+            constrainHeight: true,
+          },
+        },
+      );
+      await waitUntilReady();
+      expect(lastFrame()?.toLowerCase()).toContain(
+        'press ctrl+o to show more lines',
+      );
+      unmount();
+    });
+
+    it('detects overflow for array results exceeding available height', async () => {
+      // resultDisplay when array is expected to be AnsiLine[]
+      // AnsiLine is AnsiToken[]
+      const toolCalls = [
+        createToolCall({
+          resultDisplay: Array(5).fill([{ text: 'line', fg: 'default' }]),
+        }),
+      ];
+      const { lastFrame, unmount, waitUntilReady } = renderWithProviders(
+        <ToolGroupMessage
+          {...baseProps}
+          item={{ id: 1, type: 'tool_group', tools: toolCalls }}
+          toolCalls={toolCalls}
+          availableTerminalHeight={6}
+          isExpandable={true}
+        />,
+        {
+          config: baseMockConfig,
+          useAlternateBuffer: true,
+          uiState: {
+            constrainHeight: true,
+          },
+        },
+      );
+      await waitUntilReady();
+      expect(lastFrame()?.toLowerCase()).toContain(
+        'press ctrl+o to show more lines',
+      );
+      unmount();
+    });
+
+    it('respects ACTIVE_SHELL_MAX_LINES for focused shell tools', async () => {
+      const toolCalls = [
+        createToolCall({
+          name: 'run_shell_command',
+          status: CoreToolCallStatus.Executing,
+          ptyId: 1,
+          resultDisplay: Array(20).fill('line').join('\n'), // 20 lines > 15 (limit)
+        }),
+      ];
+      const { lastFrame, unmount, waitUntilReady } = renderWithProviders(
+        <ToolGroupMessage
+          {...baseProps}
+          item={{ id: 1, type: 'tool_group', tools: toolCalls }}
+          toolCalls={toolCalls}
+          availableTerminalHeight={100} // Plenty of terminal height
+          isExpandable={true}
+        />,
+        {
+          config: baseMockConfig,
+          useAlternateBuffer: true,
+          uiState: {
+            constrainHeight: true,
+            activePtyId: 1,
+            embeddedShellFocused: true,
+          },
+        },
+      );
+      await waitUntilReady();
+      expect(lastFrame()?.toLowerCase()).toContain(
+        'press ctrl+o to show more lines',
+      );
+      unmount();
+    });
+
+    it('does not show expansion hint when content is within limits', async () => {
+      const toolCalls = [
+        createToolCall({
+          resultDisplay: 'small result',
+        }),
+      ];
+      const { lastFrame, unmount, waitUntilReady } = renderWithProviders(
+        <ToolGroupMessage
+          {...baseProps}
+          item={{ id: 1, type: 'tool_group', tools: toolCalls }}
+          toolCalls={toolCalls}
+          availableTerminalHeight={20}
+          isExpandable={true}
+        />,
+        {
+          config: baseMockConfig,
+          useAlternateBuffer: true,
+          uiState: {
+            constrainHeight: true,
+          },
+        },
+      );
+      await waitUntilReady();
+      expect(lastFrame()).not.toContain('Press Ctrl+O to show more lines');
+      unmount();
+    });
+
+    it('hides expansion hint when constrainHeight is false', async () => {
+      const toolCalls = [
+        createToolCall({
+          resultDisplay: 'line 1\nline 2\nline 3\nline 4\nline 5',
+        }),
+      ];
+      const { lastFrame, unmount, waitUntilReady } = renderWithProviders(
+        <ToolGroupMessage
+          {...baseProps}
+          item={{ id: 1, type: 'tool_group', tools: toolCalls }}
+          toolCalls={toolCalls}
+          availableTerminalHeight={6}
+          isExpandable={true}
+        />,
+        {
+          config: baseMockConfig,
+          useAlternateBuffer: true,
+          uiState: {
+            constrainHeight: false,
+          },
+        },
+      );
+      await waitUntilReady();
+      expect(lastFrame()).not.toContain('Press Ctrl+O to show more lines');
+      unmount();
+    });
+
+    it('isolates overflow hint in ASB mode (ignores global overflow state)', async () => {
+      // In this test, the tool output is SHORT (no local overflow).
+      // We will inject a dummy ID into the global overflow state.
+      // ToolGroupMessage should still NOT show the hint because it calculates
+      // overflow locally and passes it as a prop.
+      const toolCalls = [
+        createToolCall({
+          resultDisplay: 'short result',
+        }),
+      ];
+      const { lastFrame, unmount, waitUntilReady, capturedOverflowActions } =
+        renderWithProviders(
+          <ToolGroupMessage
+            {...baseProps}
+            item={{ id: 1, type: 'tool_group', tools: toolCalls }}
+            toolCalls={toolCalls}
+            availableTerminalHeight={100}
+            isExpandable={true}
+          />,
+          {
+            config: baseMockConfig,
+            useAlternateBuffer: true,
+            uiState: {
+              constrainHeight: true,
+            },
+          },
+        );
+      await waitUntilReady();
+
+      // Manually trigger a global overflow
+      act(() => {
+        expect(capturedOverflowActions).toBeDefined();
+        capturedOverflowActions!.addOverflowingId('unrelated-global-id');
+      });
+
+      // The hint should NOT appear because ToolGroupMessage is isolated by its prop logic
+      expect(lastFrame()).not.toContain('Press Ctrl+O to show more lines');
+      unmount();
+    });
+  });
 });

packages/cli/src/ui/components/messages/ToolGroupMessage.tsx

@@ -17,10 +17,15 @@ import { ToolMessage } from './ToolMessage.js';
 import { ShellToolMessage } from './ShellToolMessage.js';
 import { theme } from '../../semantic-colors.js';
 import { useConfig } from '../../contexts/ConfigContext.js';
-import { isShellTool } from './ToolShared.js';
+import { isShellTool, isThisShellFocused } from './ToolShared.js';
 import { shouldHideToolCall } from '@google/gemini-cli-core';
 import { ShowMoreLines } from '../ShowMoreLines.js';
 import { useUIState } from '../../contexts/UIStateContext.js';
+import { useAlternateBuffer } from '../../hooks/useAlternateBuffer.js';
+import {
+  calculateShellMaxLines,
+  calculateToolContentMaxLines,
+} from '../../utils/toolLayoutUtils.js';
 import { getToolGroupBorderAppearance } from '../../utils/borderStyles.js';
 
 interface ToolGroupMessageProps {
@@ -31,6 +36,7 @@ interface ToolGroupMessageProps {
   onShellInputSubmit?: (input: string) => void;
   borderTop?: boolean;
   borderBottom?: boolean;
+  isExpandable?: boolean;
 }
 
 // Main component renders the border and maps the tools using ToolMessage
@@ -43,6 +49,7 @@ export const ToolGroupMessage: React.FC<ToolGroupMessageProps> = ({
   terminalWidth,
   borderTop: borderTopOverride,
   borderBottom: borderBottomOverride,
+  isExpandable,
 }) => {
   // Filter out tool calls that should be hidden (e.g. in-progress Ask User, or Plan Mode operations).
   const toolCalls = useMemo(
@@ -67,6 +74,7 @@ export const ToolGroupMessage: React.FC<ToolGroupMessageProps> = ({
     backgroundShells,
     pendingHistoryItems,
   } = useUIState();
+  const isAlternateBuffer = useAlternateBuffer();
 
   const { borderColor, borderDimColor } = useMemo(
     () =>
@@ -106,14 +114,6 @@ export const ToolGroupMessage: React.FC<ToolGroupMessageProps> = ({
 
   const staticHeight = /* border */ 2;
 
-  // If all tools are filtered out (e.g., in-progress AskUser tools, confirming tools),
-  // only render if we need to close a border from previous
-  // tool groups. borderBottomOverride=true means we must render the closing border;
-  // undefined or false means there's nothing to display.
-  if (visibleToolCalls.length === 0 && borderBottomOverride !== true) {
-    return null;
-  }
-
   let countToolCallsWithResults = 0;
   for (const tool of visibleToolCalls) {
     if (tool.resultDisplay !== undefined && tool.resultDisplay !== '') {
@@ -134,10 +134,81 @@ export const ToolGroupMessage: React.FC<ToolGroupMessageProps> = ({
 
   const contentWidth = terminalWidth - TOOL_MESSAGE_HORIZONTAL_MARGIN;
 
-  return (
-    // This box doesn't have a border even though it conceptually does because
-    // we need to allow the sticky headers to render the borders themselves so
-    // that the top border can be sticky.
+  /*
+   * ToolGroupMessage calculates its own overflow state locally and passes
+   * it as a prop to ShowMoreLines. This isolates it from global overflow
+   * reports in ASB mode, while allowing it to contribute to the global
+   * 'Toast' hint in Standard mode.
+   *
+   * Because of this prop-based isolation and the explicit mode-checks in
+   * AppContainer, we do not need to shadow the OverflowProvider here.
+   */
+  const hasOverflow = useMemo(() => {
+    if (!availableTerminalHeightPerToolMessage) return false;
+    return visibleToolCalls.some((tool) => {
+      const isShellToolCall = isShellTool(tool.name);
+      const isFocused = isThisShellFocused(
+        tool.name,
+        tool.status,
+        tool.ptyId,
+        activePtyId,
+        embeddedShellFocused,
+      );
+
+      let maxLines: number | undefined;
+
+      if (isShellToolCall) {
+        maxLines = calculateShellMaxLines({
+          status: tool.status,
+          isAlternateBuffer,
+          isThisShellFocused: isFocused,
+          availableTerminalHeight: availableTerminalHeightPerToolMessage,
+          constrainHeight,
+          isExpandable,
+        });
+      }
+
+      // Standard tools and Shell tools both eventually use ToolResultDisplay's logic.
+      // ToolResultDisplay uses calculateToolContentMaxLines to find the final line budget.
+      const contentMaxLines = calculateToolContentMaxLines({
+        availableTerminalHeight: availableTerminalHeightPerToolMessage,
+        isAlternateBuffer,
+        maxLinesLimit: maxLines,
+      });
+
+      if (!contentMaxLines) return false;
+
+      if (typeof tool.resultDisplay === 'string') {
+        const text = tool.resultDisplay;
+        const hasTrailingNewline = text.endsWith('\n');
+        const contentText = hasTrailingNewline ? text.slice(0, -1) : text;
+        const lineCount = contentText.split('\n').length;
+        return lineCount > contentMaxLines;
+      }
+      if (Array.isArray(tool.resultDisplay)) {
+        return tool.resultDisplay.length > contentMaxLines;
+      }
+      return false;
+    });
+  }, [
+    visibleToolCalls,
+    availableTerminalHeightPerToolMessage,
+    activePtyId,
+    embeddedShellFocused,
+    isAlternateBuffer,
+    constrainHeight,
+    isExpandable,
+  ]);
+
+  // If all tools are filtered out (e.g., in-progress AskUser tools, confirming tools),
+  // only render if we need to close a border from previous
+  // tool groups. borderBottomOverride=true means we must render the closing border;
+  // undefined or false means there's nothing to display.
+  if (visibleToolCalls.length === 0 && borderBottomOverride !== true) {
+    return null;
+  }
+
+  const content = (
     <Box
       flexDirection="column"
       /*
@@ -148,7 +219,6 @@ export const ToolGroupMessage: React.FC<ToolGroupMessageProps> = ({
     */
       width={terminalWidth}
       paddingRight={TOOL_MESSAGE_HORIZONTAL_MARGIN}
-      marginBottom={borderBottomOverride === false ? 0 : 1}
     >
       {visibleToolCalls.map((tool, index) => {
         const isFirst = index === 0;
@@ -165,6 +235,7 @@ export const ToolGroupMessage: React.FC<ToolGroupMessageProps> = ({
               : isFirst,
           borderColor,
           borderDimColor,
+          isExpandable,
         };
 
         return (
@@ -179,6 +250,7 @@ export const ToolGroupMessage: React.FC<ToolGroupMessageProps> = ({
             ) : (
               <ToolMessage {...commonProps} />
             )}
+            {tool.outputFile && (
               <Box
                 borderLeft={true}
                 borderRight={true}
@@ -191,14 +263,13 @@ export const ToolGroupMessage: React.FC<ToolGroupMessageProps> = ({
                 paddingLeft={1}
                 paddingRight={1}
               >
-              {tool.outputFile && (
                 <Box>
                   <Text color={theme.text.primary}>
                     Output too long and was saved to: {tool.outputFile}
                   </Text>
                 </Box>
-              )}
               </Box>
+            )}
           </Box>
         );
       })}
@@ -222,8 +293,13 @@ export const ToolGroupMessage: React.FC<ToolGroupMessageProps> = ({
         )
       }
       {(borderBottomOverride ?? true) && visibleToolCalls.length > 0 && (
-        <ShowMoreLines constrainHeight={constrainHeight} />
+        <ShowMoreLines
+          constrainHeight={constrainHeight && !!isExpandable}
+          isOverflowing={hasOverflow}
+        />
       )}
     </Box>
   );
+
+  return content;
 };

packages/cli/src/ui/components/messages/ToolOverflowConsistencyChecks.test.tsx

@@ -0,0 +1,115 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { describe, it, expect } from 'vitest';
+import { ToolGroupMessage } from './ToolGroupMessage.js';
+import { renderWithProviders } from '../../../test-utils/render.js';
+import { StreamingState, type IndividualToolCallDisplay } from '../../types.js';
+import { OverflowProvider } from '../../contexts/OverflowContext.js';
+import { waitFor } from '../../../test-utils/async.js';
+import { CoreToolCallStatus } from '@google/gemini-cli-core';
+
+describe('ToolOverflowConsistencyChecks: ToolGroupMessage and ToolResultDisplay synchronization', () => {
+  it('should ensure explicit hasOverflow calculation is consistent with ToolResultDisplay truncation in Alternate Buffer (ASB) mode', async () => {
+    /**
+     * Logic:
+     * 1. availableTerminalHeight(13) - staticHeight(3) = 10 lines per tool.
+     * 2. ASB mode reserves 1 + 6 = 7 lines.
+     * 3. Line budget = 10 - 7 = 3 lines.
+     * 4. 5 lines of output > 3 lines budget => hasOverflow should be TRUE.
+     */
+
+    const lines = Array.from({ length: 5 }, (_, i) => `line ${i + 1}`);
+    const resultDisplay = lines.join('\n');
+
+    const toolCalls: IndividualToolCallDisplay[] = [
+      {
+        callId: 'call-1',
+        name: 'test-tool',
+        description: 'a test tool',
+        status: CoreToolCallStatus.Success,
+        resultDisplay,
+        confirmationDetails: undefined,
+      },
+    ];
+
+    const { lastFrame } = renderWithProviders(
+      <OverflowProvider>
+        <ToolGroupMessage
+          item={{ id: 1, type: 'tool_group', tools: toolCalls }}
+          toolCalls={toolCalls}
+          availableTerminalHeight={13}
+          terminalWidth={80}
+          isExpandable={true}
+        />
+      </OverflowProvider>,
+      {
+        uiState: {
+          streamingState: StreamingState.Idle,
+          constrainHeight: true,
+        },
+        useAlternateBuffer: true,
+      },
+    );
+
+    // In ASB mode, the hint should appear because hasOverflow is now correctly calculated.
+    await waitFor(() =>
+      expect(lastFrame()?.toLowerCase()).toContain(
+        'press ctrl+o to show more lines',
+      ),
+    );
+  });
+
+  it('should ensure explicit hasOverflow calculation is consistent with ToolResultDisplay truncation in Standard mode', async () => {
+    /**
+     * Logic:
+     * 1. availableTerminalHeight(13) - staticHeight(3) = 10 lines per tool.
+     * 2. Standard mode reserves 1 + 2 = 3 lines.
+     * 3. Line budget = 10 - 3 = 7 lines.
+     * 4. 9 lines of output > 7 lines budget => hasOverflow should be TRUE.
+     */
+
+    const lines = Array.from({ length: 9 }, (_, i) => `line ${i + 1}`);
+    const resultDisplay = lines.join('\n');
+
+    const toolCalls: IndividualToolCallDisplay[] = [
+      {
+        callId: 'call-1',
+        name: 'test-tool',
+        description: 'a test tool',
+        status: CoreToolCallStatus.Success,
+        resultDisplay,
+        confirmationDetails: undefined,
+      },
+    ];
+
+    const { lastFrame } = renderWithProviders(
+      <OverflowProvider>
+        <ToolGroupMessage
+          item={{ id: 1, type: 'tool_group', tools: toolCalls }}
+          toolCalls={toolCalls}
+          availableTerminalHeight={13}
+          terminalWidth={80}
+          isExpandable={true}
+        />
+      </OverflowProvider>,
+      {
+        uiState: {
+          streamingState: StreamingState.Idle,
+          constrainHeight: true,
+        },
+        useAlternateBuffer: false,
+      },
+    );
+
+    // Verify truncation is occurring (standard mode uses MaxSizedBox)
+    await waitFor(() => expect(lastFrame()).toContain('hidden ...'));
+
+    // In Standard mode, ToolGroupMessage calculates hasOverflow correctly now.
+    // While Standard mode doesn't render the inline hint (ShowMoreLines returns null),
+    // the logic inside ToolGroupMessage is now synchronized.
+  });
+});

packages/cli/src/ui/components/messages/ToolResultDisplay.test.tsx

@@ -277,21 +277,47 @@ describe('ToolResultDisplay', () => {
           inverse: false,
         },
       ],
+      [
+        {
+          text: 'Line 4',
+          fg: '',
+          bg: '',
+          bold: false,
+          italic: false,
+          underline: false,
+          dim: false,
+          inverse: false,
+        },
+      ],
+      [
+        {
+          text: 'Line 5',
+          fg: '',
+          bg: '',
+          bold: false,
+          italic: false,
+          underline: false,
+          dim: false,
+          inverse: false,
+        },
+      ],
     ];
     const { lastFrame, waitUntilReady, unmount } = renderWithProviders(
       <ToolResultDisplay
         resultDisplay={ansiResult}
         terminalWidth={80}
         availableTerminalHeight={20}
-        maxLines={2}
+        maxLines={3}
       />,
     );
     await waitUntilReady();
     const output = lastFrame();
 
     expect(output).not.toContain('Line 1');
-    expect(output).toContain('Line 2');
-    expect(output).toContain('Line 3');
+    expect(output).not.toContain('Line 2');
+    expect(output).not.toContain('Line 3');
+    expect(output).toContain('Line 4');
+    expect(output).toContain('Line 5');
     unmount();
   });
 

packages/cli/src/ui/components/messages/ToolResultDisplay.tsx

@@ -19,10 +19,7 @@ import { Scrollable } from '../shared/Scrollable.js';
 import { ScrollableList } from '../shared/ScrollableList.js';
 import { SCROLL_TO_ITEM_END } from '../shared/VirtualizedList.js';
 import { ACTIVE_SHELL_MAX_LINES } from '../../constants.js';
-
-const STATIC_HEIGHT = 1;
-const RESERVED_LINE_COUNT = 6; // for tool name, status, padding, and 'ShowMoreLines' hint
-const MIN_LINES_SHOWN = 2; // show at least this many lines
+import { calculateToolContentMaxLines } from '../../utils/toolLayoutUtils.js';
 
 // Large threshold to ensure we don't cause performance issues for very large
 // outputs that will get truncated further MaxSizedBox anyway.
@@ -53,16 +50,11 @@ export const ToolResultDisplay: React.FC<ToolResultDisplayProps> = ({
   const { renderMarkdown } = useUIState();
   const isAlternateBuffer = useAlternateBuffer();
 
-  let availableHeight = availableTerminalHeight
-    ? Math.max(
-        availableTerminalHeight - STATIC_HEIGHT - RESERVED_LINE_COUNT,
-        MIN_LINES_SHOWN + 1, // enforce minimum lines shown
-      )
-    : undefined;
-
-  if (maxLines && availableHeight) {
-    availableHeight = Math.min(availableHeight, maxLines);
-  }
+  const availableHeight = calculateToolContentMaxLines({
+    availableTerminalHeight,
+    isAlternateBuffer,
+    maxLinesLimit: maxLines,
+  });
 
   const combinedPaddingAndBorderWidth = 4;
   const childWidth = terminalWidth - combinedPaddingAndBorderWidth;
@@ -81,7 +73,8 @@ export const ToolResultDisplay: React.FC<ToolResultDisplayProps> = ({
     [],
   );
 
-  const truncatedResultDisplay = React.useMemo(() => {
+  const { truncatedResultDisplay, hiddenLinesCount } = React.useMemo(() => {
+    let hiddenLines = 0;
     // Only truncate string output if not in alternate buffer mode to ensure
     // we can scroll through the full output.
     if (typeof resultDisplay === 'string' && !isAlternateBuffer) {
@@ -94,14 +87,29 @@ export const ToolResultDisplay: React.FC<ToolResultDisplayProps> = ({
         const contentText = hasTrailingNewline ? text.slice(0, -1) : text;
         const lines = contentText.split('\n');
         if (lines.length > maxLines) {
+          // We will have a label from MaxSizedBox. Reserve space for it.
+          const targetLines = Math.max(1, maxLines - 1);
+          hiddenLines = lines.length - targetLines;
           text =
-            lines.slice(-maxLines).join('\n') +
+            lines.slice(-targetLines).join('\n') +
             (hasTrailingNewline ? '\n' : '');
         }
       }
-      return text;
+      return { truncatedResultDisplay: text, hiddenLinesCount: hiddenLines };
     }
-    return resultDisplay;
+
+    if (Array.isArray(resultDisplay) && !isAlternateBuffer && maxLines) {
+      if (resultDisplay.length > maxLines) {
+        // We will have a label from MaxSizedBox. Reserve space for it.
+        const targetLines = Math.max(1, maxLines - 1);
+        return {
+          truncatedResultDisplay: resultDisplay.slice(-targetLines),
+          hiddenLinesCount: resultDisplay.length - targetLines,
+        };
+      }
+    }
+
+    return { truncatedResultDisplay: resultDisplay, hiddenLinesCount: 0 };
   }, [resultDisplay, isAlternateBuffer, maxLines]);
 
   if (!truncatedResultDisplay) return null;
@@ -229,7 +237,11 @@ export const ToolResultDisplay: React.FC<ToolResultDisplayProps> = ({
 
   return (
     <Box width={childWidth} flexDirection="column">
-      <MaxSizedBox maxHeight={availableHeight} maxWidth={childWidth}>
+      <MaxSizedBox
+        maxHeight={availableHeight}
+        maxWidth={childWidth}
+        additionalHiddenLinesCount={hiddenLinesCount}
+      >
         {content}
       </MaxSizedBox>
     </Box>

packages/cli/src/ui/components/messages/ToolResultDisplayOverflow.test.tsx

@@ -39,6 +39,7 @@ describe('ToolResultDisplay Overflow', () => {
           toolCalls={toolCalls}
           availableTerminalHeight={15} // Small height to force overflow
           terminalWidth={80}
+          isExpandable={true}
         />
       </OverflowProvider>,
       {
@@ -46,26 +47,28 @@ describe('ToolResultDisplay Overflow', () => {
           streamingState: StreamingState.Idle,
           constrainHeight: true,
         },
-        useAlternateBuffer: false,
+        useAlternateBuffer: true,
       },
     );
 
     // ResizeObserver might take a tick
     await waitFor(() =>
-      expect(lastFrame()).toContain('Press ctrl-o to show more lines'),
+      expect(lastFrame()?.toLowerCase()).toContain(
+        'press ctrl+o to show more lines',
+      ),
     );
 
     const frame = lastFrame();
     expect(frame).toBeDefined();
     if (frame) {
-      expect(frame).toContain('Press ctrl-o to show more lines');
+      expect(frame.toLowerCase()).toContain('press ctrl+o to show more lines');
       // Ensure it's AFTER the bottom border
       const linesOfOutput = frame.split('\n');
       const bottomBorderIndex = linesOfOutput.findLastIndex((l) =>
         l.includes('╰─'),
       );
       const hintIndex = linesOfOutput.findIndex((l) =>
-        l.includes('Press ctrl-o to show more lines'),
+        l.toLowerCase().includes('press ctrl+o to show more lines'),
       );
       expect(hintIndex).toBeGreaterThan(bottomBorderIndex);
       expect(frame).toMatchSnapshot();

packages/cli/src/ui/components/messages/__snapshots__/ShellToolMessage.test.tsx.snap

@@ -1,6 +1,6 @@
 // Vitest Snapshot v1, https://vitest.dev/guide/snapshot.html
 
-exports[`<ShellToolMessage /> > Height Constraints > defaults to ACTIVE_SHELL_MAX_LINES when availableTerminalHeight is undefined 1`] = `
+exports[`<ShellToolMessage /> > Height Constraints > defaults to ACTIVE_SHELL_MAX_LINES in alternate buffer when availableTerminalHeight is undefined 1`] = `
 "╭──────────────────────────────────────────────────────────────────────────────╮
 │ ⊷  Shell Command A shell command                                             │
 │                                                                              │
@@ -22,6 +22,113 @@ exports[`<ShellToolMessage /> > Height Constraints > defaults to ACTIVE_SHELL_MA
 "
 `;
 
+exports[`<ShellToolMessage /> > Height Constraints > fully expands in alternate buffer mode when constrainHeight is false and isExpandable is true 1`] = `
+"╭──────────────────────────────────────────────────────────────────────────────╮
+│ ✓  Shell Command A shell command                                             │
+│                                                                              │
+│ Line 1                                                                       │
+│ Line 2                                                                       │
+│ Line 3                                                                       │
+│ Line 4                                                                       │
+│ Line 5                                                                       │
+│ Line 6                                                                       │
+│ Line 7                                                                       │
+│ Line 8                                                                       │
+│ Line 9                                                                       │
+│ Line 10                                                                      │
+│ Line 11                                                                      │
+│ Line 12                                                                      │
+│ Line 13                                                                      │
+│ Line 14                                                                      │
+│ Line 15                                                                      │
+│ Line 16                                                                      │
+│ Line 17                                                                      │
+│ Line 18                                                                      │
+│ Line 19                                                                      │
+│ Line 20                                                                      │
+│ Line 21                                                                      │
+│ Line 22                                                                      │
+│ Line 23                                                                      │
+│ Line 24                                                                      │
+│ Line 25                                                                      │
+│ Line 26                                                                      │
+│ Line 27                                                                      │
+│ Line 28                                                                      │
+│ Line 29                                                                      │
+│ Line 30                                                                      │
+│ Line 31                                                                      │
+│ Line 32                                                                      │
+│ Line 33                                                                      │
+│ Line 34                                                                      │
+│ Line 35                                                                      │
+│ Line 36                                                                      │
+│ Line 37                                                                      │
+│ Line 38                                                                      │
+│ Line 39                                                                      │
+│ Line 40                                                                      │
+│ Line 41                                                                      │
+│ Line 42                                                                      │
+│ Line 43                                                                      │
+│ Line 44                                                                      │
+│ Line 45                                                                      │
+│ Line 46                                                                      │
+│ Line 47                                                                      │
+│ Line 48                                                                      │
+│ Line 49                                                                      │
+│ Line 50                                                                      │
+│ Line 51                                                                      │
+│ Line 52                                                                      │
+│ Line 53                                                                      │
+│ Line 54                                                                      │
+│ Line 55                                                                      │
+│ Line 56                                                                      │
+│ Line 57                                                                      │
+│ Line 58                                                                      │
+│ Line 59                                                                      │
+│ Line 60                                                                      │
+│ Line 61                                                                      │
+│ Line 62                                                                      │
+│ Line 63                                                                      │
+│ Line 64                                                                      │
+│ Line 65                                                                      │
+│ Line 66                                                                      │
+│ Line 67                                                                      │
+│ Line 68                                                                      │
+│ Line 69                                                                      │
+│ Line 70                                                                      │
+│ Line 71                                                                      │
+│ Line 72                                                                      │
+│ Line 73                                                                      │
+│ Line 74                                                                      │
+│ Line 75                                                                      │
+│ Line 76                                                                      │
+│ Line 77                                                                      │
+│ Line 78                                                                      │
+│ Line 79                                                                      │
+│ Line 80                                                                      │
+│ Line 81                                                                      │
+│ Line 82                                                                      │
+│ Line 83                                                                      │
+│ Line 84                                                                      │
+│ Line 85                                                                      │
+│ Line 86                                                                      │
+│ Line 87                                                                      │
+│ Line 88                                                                      │
+│ Line 89                                                                      │
+│ Line 90                                                                      │
+│ Line 91                                                                      │
+│ Line 92                                                                      │
+│ Line 93                                                                      │
+│ Line 94                                                                      │
+│ Line 95                                                                      │
+│ Line 96                                                                      │
+│ Line 97                                                                      │
+│ Line 98                                                                      │
+│ Line 99                                                                      │
+│ Line 100                                                                     │
+"
+`;
+
 exports[`<ShellToolMessage /> > Height Constraints > respects availableTerminalHeight when it is smaller than ACTIVE_SHELL_MAX_LINES 1`] = `
 "╭──────────────────────────────────────────────────────────────────────────────╮
 │ ⊷  Shell Command A shell command                                             │
@@ -37,6 +144,28 @@ exports[`<ShellToolMessage /> > Height Constraints > respects availableTerminalH
 "
 `;
 
+exports[`<ShellToolMessage /> > Height Constraints > stays constrained in alternate buffer mode when isExpandable is false even if constrainHeight is false 1`] = `
+"╭──────────────────────────────────────────────────────────────────────────────╮
+│ ✓  Shell Command A shell command                                             │
+│                                                                              │
+│ Line 86                                                                      │
+│ Line 87                                                                      │
+│ Line 88                                                                      │
+│ Line 89                                                                      │
+│ Line 90                                                                      │
+│ Line 91                                                                      │
+│ Line 92                                                                      │
+│ Line 93                                                                      │
+│ Line 94                                                                      │
+│ Line 95                                                                      │
+│ Line 96                                                                      │
+│ Line 97                                                                      │
+│ Line 98                                                                    ▄ │
+│ Line 99                                                                    █ │
+│ Line 100                                                                   █ │
+"
+`;
+
 exports[`<ShellToolMessage /> > Height Constraints > uses ACTIVE_SHELL_MAX_LINES when availableTerminalHeight is large 1`] = `
 "╭──────────────────────────────────────────────────────────────────────────────╮
 │ ⊷  Shell Command A shell command                                             │
@@ -161,7 +290,6 @@ exports[`<ShellToolMessage /> > Height Constraints > uses full availableTerminal
 │ Line 98                                                                    █ │
 │ Line 99                                                                    █ │
 │ Line 100                                                                   █ │
-│                                                                              │
 "
 `;
 
@@ -170,7 +298,6 @@ exports[`<ShellToolMessage /> > Snapshots > renders in Alternate Buffer mode whi
 │ ⊷  Shell Command A shell command                      (Shift+Tab to unfocus) │
 │                                                                              │
 │ Test result                                                                  │
-│                                                                              │
 "
 `;
 

packages/cli/src/ui/components/messages/__snapshots__/ToolGroupMessage.test.tsx.snap

@@ -55,13 +55,13 @@ exports[`<ToolGroupMessage /> > Golden Snapshots > renders header when scrolled
 "╭──────────────────────────────────────────────────────────────────────────╮
 │ ✓  tool-1 Description 1. This is a long description that will need to b… │
 │──────────────────────────────────────────────────────────────────────────│
-│                                                                          │                       ▄
+│ line5                                                                    │                       █
+│                                                                          │                       █
 │ ✓  tool-2 Description 2                                                  │                       █
 │                                                                          │                       █
 │ line1                                                                    │                       █
 │ line2                                                                    │                       █
 ╰──────────────────────────────────────────────────────────────────────────╯                       █
-                                                                                                   █
 "
 `;
 
@@ -111,12 +111,12 @@ exports[`<ToolGroupMessage /> > Golden Snapshots > renders tool call with output
 `;
 
 exports[`<ToolGroupMessage /> > Golden Snapshots > renders two tool groups where only the last line of the previous group is visible 1`] = `
-"╭──────────────────────────────────────────────────────────────────────────╮
+"╰──────────────────────────────────────────────────────────────────────────╯
+╭──────────────────────────────────────────────────────────────────────────╮
 │ ✓  tool-2 Description 2                                                  │
-│                                                                          │
-│ line1                                                                    │                       ▄
+│                                                                          │                       ▄
+│ line1                                                                    │                       █
 ╰──────────────────────────────────────────────────────────────────────────╯                       █
-                                                                                                   █
 "
 `;
 

packages/cli/src/ui/components/messages/__snapshots__/ToolResultDisplay.test.tsx.snap

@@ -37,7 +37,11 @@ exports[`ToolResultDisplay > renders string result as plain text when renderOutp
 `;
 
 exports[`ToolResultDisplay > truncates very long string results 1`] = `
-"... first 252 lines hidden ...
+"... first 248 lines hidden ...
+aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
 aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
 aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
 aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa

packages/cli/src/ui/components/messages/__snapshots__/ToolResultDisplayOverflow.test.tsx.snap

@@ -4,13 +4,13 @@ exports[`ToolResultDisplay Overflow > should display "press ctrl-o" hint when co
 "╭──────────────────────────────────────────────────────────────────────────╮
 │ ✓  test-tool a test tool                                                 │
 │                                                                          │
-│ ... first 45 lines hidden ...                                            │
+│ line 45                                                                  │
 │ line 46                                                                  │
 │ line 47                                                                  │
 │ line 48                                                                  │
 │ line 49                                                                  │
-│ line 50                                                                  │
+│ line 50                                                                █ │
 ╰──────────────────────────────────────────────────────────────────────────╯
- Press ctrl-o to show more lines
+ Press Ctrl+O to show more lines
 "
 `;

packages/cli/src/ui/components/messages/__snapshots__/ToolStickyHeaderRegression.test.tsx.snap

@@ -2,7 +2,7 @@
 
 exports[`ToolMessage Sticky Header Regression > verifies that ShellToolMessage in a ToolGroupMessage in a ScrollableList has sticky headers 1`] = `
 "╭────────────────────────────────────────────────────────────────────────╮     █
-│ ✓  Shell Command Description for Shell Command                         │     ▀
+│ ✓  Shell Command Description for Shell Command                         │     █
 │                                                                        │
 │ shell-01                                                               │
 │ shell-02                                                               │
@@ -11,7 +11,7 @@ exports[`ToolMessage Sticky Header Regression > verifies that ShellToolMessage i
 
 exports[`ToolMessage Sticky Header Regression > verifies that ShellToolMessage in a ToolGroupMessage in a ScrollableList has sticky headers 2`] = `
 "╭────────────────────────────────────────────────────────────────────────╮
-│ ✓  Shell Command Description for Shell Command                         │
+│ ✓  Shell Command Description for Shell Command                         │     ▄
 │────────────────────────────────────────────────────────────────────────│     █
 │ shell-06                                                               │     ▀
 │ shell-07                                                               │

packages/cli/src/ui/constants.ts

@@ -33,6 +33,7 @@ export const WARNING_PROMPT_DURATION_MS = 3000;
 export const QUEUE_ERROR_DISPLAY_DURATION_MS = 3000;
 export const SHELL_ACTION_REQUIRED_TITLE_DELAY_MS = 30000;
 export const SHELL_SILENT_WORKING_TITLE_DELAY_MS = 120000;
+export const EXPAND_HINT_DURATION_MS = 5000;
 
 export const DEFAULT_BACKGROUND_OPACITY = 0.16;
 export const DEFAULT_INPUT_BACKGROUND_OPACITY = 0.24;

packages/cli/src/ui/contexts/OverflowContext.tsx

@@ -13,13 +13,14 @@ import {
   useMemo,
 } from 'react';
 
-interface OverflowState {
+export interface OverflowState {
   overflowingIds: ReadonlySet<string>;
 }
 
-interface OverflowActions {
+export interface OverflowActions {
   addOverflowingId: (id: string) => void;
   removeOverflowingId: (id: string) => void;
+  reset: () => void;
 }
 
 const OverflowStateContext = createContext<OverflowState | undefined>(
@@ -63,6 +64,10 @@ export const OverflowProvider: React.FC<{ children: React.ReactNode }> = ({
     });
   }, []);
 
+  const reset = useCallback(() => {
+    setOverflowingIds(new Set());
+  }, []);
+
   const stateValue = useMemo(
     () => ({
       overflowingIds,
@@ -74,8 +79,9 @@ export const OverflowProvider: React.FC<{ children: React.ReactNode }> = ({
     () => ({
       addOverflowingId,
       removeOverflowingId,
+      reset,
     }),
-    [addOverflowingId, removeOverflowingId],
+    [addOverflowingId, removeOverflowingId, reset],
   );
 
   return (

packages/cli/src/ui/contexts/UIStateContext.tsx

@@ -182,6 +182,7 @@ export interface UIState {
   isBackgroundShellListOpen: boolean;
   adminSettingsChanged: boolean;
   newAgents: AgentDefinition[] | null;
+  showIsExpandableHint: boolean;
   hintMode: boolean;
   hintBuffer: string;
   transientMessage: {

packages/cli/src/ui/utils/CodeColorizer.tsx

@@ -22,7 +22,6 @@ import {
 } from '../components/shared/MaxSizedBox.js';
 import type { LoadedSettings } from '../../config/settings.js';
 import { debugLogger } from '@google/gemini-cli-core';
-import { isAlternateBufferEnabled } from '../hooks/useAlternateBuffer.js';
 
 // Configure theming and parsing utilities.
 const lowlight = createLowlight(common);
@@ -152,7 +151,6 @@ export function colorizeCode({
     ? false
     : settings.merged.ui.showLineNumbers;
 
-  const useMaxSizedBox = !isAlternateBufferEnabled(settings);
   try {
     // Render the HAST tree using the adapted theme
     // Apply the theme's default foreground color to the top-level Text element
@@ -162,7 +160,7 @@ export function colorizeCode({
     let hiddenLinesCount = 0;
 
     // Optimization to avoid highlighting lines that cannot possibly be displayed.
-    if (availableHeight !== undefined && useMaxSizedBox) {
+    if (availableHeight !== undefined) {
       availableHeight = Math.max(availableHeight, MINIMUM_MAX_HEIGHT);
       if (lines.length > availableHeight) {
         const sliceIndex = lines.length - availableHeight;
@@ -200,7 +198,7 @@ export function colorizeCode({
       );
     });
 
-    if (useMaxSizedBox) {
+    if (availableHeight !== undefined) {
       return (
         <MaxSizedBox
           maxHeight={availableHeight}
@@ -244,7 +242,7 @@ export function colorizeCode({
       </Box>
     ));
 
-    if (useMaxSizedBox) {
+    if (availableHeight !== undefined) {
       return (
         <MaxSizedBox
           maxHeight={availableHeight}

packages/cli/src/ui/utils/toolLayoutUtils.ts

@@ -0,0 +1,110 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import {
+  ACTIVE_SHELL_MAX_LINES,
+  COMPLETED_SHELL_MAX_LINES,
+} from '../constants.js';
+import { CoreToolCallStatus } from '@google/gemini-cli-core';
+
+/**
+ * Constants used for calculating available height for tool results.
+ * These MUST be kept in sync between ToolGroupMessage (for overflow detection)
+ * and ToolResultDisplay (for actual truncation).
+ */
+export const TOOL_RESULT_STATIC_HEIGHT = 1;
+export const TOOL_RESULT_ASB_RESERVED_LINE_COUNT = 6;
+export const TOOL_RESULT_STANDARD_RESERVED_LINE_COUNT = 2;
+export const TOOL_RESULT_MIN_LINES_SHOWN = 2;
+
+/**
+ * Calculates the final height available for the content of a tool result display.
+ *
+ * This accounts for:
+ * 1. The static height of the tool message (name, status line).
+ * 2. Reserved space for hints and padding (different in ASB vs Standard mode).
+ * 3. Enforcing a minimum number of lines shown.
+ */
+export function calculateToolContentMaxLines(options: {
+  availableTerminalHeight: number | undefined;
+  isAlternateBuffer: boolean;
+  maxLinesLimit?: number;
+}): number | undefined {
+  const { availableTerminalHeight, isAlternateBuffer, maxLinesLimit } = options;
+
+  const reservedLines = isAlternateBuffer
+    ? TOOL_RESULT_ASB_RESERVED_LINE_COUNT
+    : TOOL_RESULT_STANDARD_RESERVED_LINE_COUNT;
+
+  let contentHeight = availableTerminalHeight
+    ? Math.max(
+        availableTerminalHeight - TOOL_RESULT_STATIC_HEIGHT - reservedLines,
+        TOOL_RESULT_MIN_LINES_SHOWN + 1,
+      )
+    : undefined;
+
+  if (maxLinesLimit) {
+    contentHeight =
+      contentHeight !== undefined
+        ? Math.min(contentHeight, maxLinesLimit)
+        : maxLinesLimit;
+  }
+
+  return contentHeight;
+}
+
+/**
+ * Calculates the maximum number of lines to display for shell output.
+ *
+ * This logic distinguishes between:
+ * 1. Process Status: Active (Executing) vs Completed.
+ * 2. UI Focus: Whether the user is currently interacting with the shell.
+ * 3. Expansion State: Whether the user has explicitly requested to "Show More Lines" (CTRL+O).
+ */
+export function calculateShellMaxLines(options: {
+  status: CoreToolCallStatus;
+  isAlternateBuffer: boolean;
+  isThisShellFocused: boolean;
+  availableTerminalHeight: number | undefined;
+  constrainHeight: boolean;
+  isExpandable: boolean | undefined;
+}): number | undefined {
+  const {
+    status,
+    isAlternateBuffer,
+    isThisShellFocused,
+    availableTerminalHeight,
+    constrainHeight,
+    isExpandable,
+  } = options;
+
+  // 1. If the user explicitly requested expansion (unconstrained), remove all caps.
+  if (!constrainHeight && isExpandable) {
+    return undefined;
+  }
+
+  // 2. Handle cases where height is unknown (Standard mode history).
+  if (availableTerminalHeight === undefined) {
+    return isAlternateBuffer ? ACTIVE_SHELL_MAX_LINES : undefined;
+  }
+
+  const maxLinesBasedOnHeight = Math.max(1, availableTerminalHeight - 2);
+
+  // 3. Handle ASB mode focus expansion.
+  // We allow a focused shell in ASB mode to take up the full available height,
+  // BUT only if we aren't trying to maintain a constrained view (e.g., history items).
+  if (isAlternateBuffer && isThisShellFocused && !constrainHeight) {
+    return maxLinesBasedOnHeight;
+  }
+
+  // 4. Fall back to process-based constants.
+  const isExecuting = status === CoreToolCallStatus.Executing;
+  const shellMaxLinesLimit = isExecuting
+    ? ACTIVE_SHELL_MAX_LINES
+    : COMPLETED_SHELL_MAX_LINES;
+
+  return Math.min(maxLinesBasedOnHeight, shellMaxLinesLimit);
+}