feat: Implement background shell commands (#14849)

packages/cli/src/ui/hooks/__snapshots__/useToolScheduler.test.ts.snap

@@ -4,6 +4,7 @@ exports[`useReactToolScheduler > should handle live output updates 1`] = `
 {
   "callId": "liveCall",
   "contentLength": 12,
+  "data": undefined,
   "error": undefined,
   "errorType": undefined,
   "outputFile": undefined,
@@ -26,6 +27,7 @@ exports[`useReactToolScheduler > should handle tool requiring confirmation - app
 {
   "callId": "callConfirm",
   "contentLength": 16,
+  "data": undefined,
   "error": undefined,
   "errorType": undefined,
   "outputFile": undefined,
@@ -75,6 +77,7 @@ exports[`useReactToolScheduler > should schedule and execute a tool call success
 {
   "callId": "call1",
   "contentLength": 11,
+  "data": undefined,
   "error": undefined,
   "errorType": undefined,
   "outputFile": undefined,

packages/cli/src/ui/hooks/shellCommandProcessor.test.tsx

@@ -19,12 +19,34 @@ import {
 
 const mockIsBinary = vi.hoisted(() => vi.fn());
 const mockShellExecutionService = vi.hoisted(() => vi.fn());
+const mockShellKill = vi.hoisted(() => vi.fn());
+const mockShellBackground = vi.hoisted(() => vi.fn());
+const mockShellSubscribe = vi.hoisted(() =>
+  vi.fn<
+    (pid: number, listener: (event: ShellOutputEvent) => void) => () => void
+  >(() => vi.fn()),
+); // Returns unsubscribe
+const mockShellOnExit = vi.hoisted(() =>
+  vi.fn<
+    (
+      pid: number,
+      callback: (exitCode: number, signal?: number) => void,
+    ) => () => void
+  >(() => vi.fn()),
+);
+
 vi.mock('@google/gemini-cli-core', async (importOriginal) => {
   const actual =
     await importOriginal<typeof import('@google/gemini-cli-core')>();
   return {
     ...actual,
-    ShellExecutionService: { execute: mockShellExecutionService },
+    ShellExecutionService: {
+      execute: mockShellExecutionService,
+      kill: mockShellKill,
+      background: mockShellBackground,
+      subscribe: mockShellSubscribe,
+      onExit: mockShellOnExit,
+    },
     isBinary: mockIsBinary,
   };
 });
@@ -113,7 +135,13 @@ describe('useShellCommandProcessor', () => {
 
   const renderProcessorHook = () => {
     let hookResult: ReturnType<typeof useShellCommandProcessor>;
-    function TestComponent() {
+    let renderCount = 0;
+    function TestComponent({
+      isWaitingForConfirmation,
+    }: {
+      isWaitingForConfirmation?: boolean;
+    }) {
+      renderCount++;
       hookResult = useShellCommandProcessor(
         addItemToHistoryMock,
         setPendingHistoryItemMock,
@@ -122,16 +150,25 @@ describe('useShellCommandProcessor', () => {
         mockConfig,
         mockGeminiClient,
         setShellInputFocusedMock,
+        undefined,
+        undefined,
+        undefined,
+        isWaitingForConfirmation,
       );
       return null;
     }
-    render(<TestComponent />);
+    const { rerender } = render(<TestComponent />);
     return {
       result: {
         get current() {
           return hookResult;
         },
       },
+      getRenderCount: () => renderCount,
+      rerender: (isWaitingForConfirmation?: boolean) =>
+        rerender(
+          <TestComponent isWaitingForConfirmation={isWaitingForConfirmation} />,
+        ),
     };
   };
 
@@ -723,4 +760,403 @@ describe('useShellCommandProcessor', () => {
       expect(result.current.activeShellPtyId).toBeNull();
     });
   });
+
+  describe('Background Shell Management', () => {
+    it('should register a background shell and update count', async () => {
+      const { result } = renderProcessorHook();
+
+      act(() => {
+        result.current.registerBackgroundShell(1001, 'bg-cmd', 'initial');
+      });
+
+      expect(result.current.backgroundShellCount).toBe(1);
+      const shell = result.current.backgroundShells.get(1001);
+      expect(shell).toEqual(
+        expect.objectContaining({
+          pid: 1001,
+          command: 'bg-cmd',
+          output: 'initial',
+        }),
+      );
+      expect(mockShellOnExit).toHaveBeenCalledWith(1001, expect.any(Function));
+      expect(mockShellSubscribe).toHaveBeenCalledWith(
+        1001,
+        expect.any(Function),
+      );
+    });
+
+    it('should toggle background shell visibility', async () => {
+      const { result } = renderProcessorHook();
+
+      act(() => {
+        result.current.registerBackgroundShell(1001, 'bg-cmd', 'initial');
+      });
+
+      expect(result.current.isBackgroundShellVisible).toBe(false);
+
+      act(() => {
+        result.current.toggleBackgroundShell();
+      });
+
+      expect(result.current.isBackgroundShellVisible).toBe(true);
+
+      act(() => {
+        result.current.toggleBackgroundShell();
+      });
+
+      expect(result.current.isBackgroundShellVisible).toBe(false);
+    });
+
+    it('should show info message when toggling background shells if none are active', async () => {
+      const { result } = renderProcessorHook();
+
+      act(() => {
+        result.current.toggleBackgroundShell();
+      });
+
+      expect(addItemToHistoryMock).toHaveBeenCalledWith(
+        expect.objectContaining({
+          type: 'info',
+          text: 'No background shells are currently active.',
+        }),
+        expect.any(Number),
+      );
+      expect(result.current.isBackgroundShellVisible).toBe(false);
+    });
+
+    it('should dismiss a background shell and remove it from state', async () => {
+      const { result } = renderProcessorHook();
+
+      act(() => {
+        result.current.registerBackgroundShell(1001, 'bg-cmd', 'initial');
+      });
+
+      act(() => {
+        result.current.dismissBackgroundShell(1001);
+      });
+
+      expect(mockShellKill).toHaveBeenCalledWith(1001);
+      expect(result.current.backgroundShellCount).toBe(0);
+      expect(result.current.backgroundShells.has(1001)).toBe(false);
+    });
+
+    it('should handle backgrounding the current shell', async () => {
+      // Simulate an active shell
+      mockShellExecutionService.mockImplementation((_cmd, _cwd, callback) => {
+        mockShellOutputCallback = callback;
+        return Promise.resolve({
+          pid: 555,
+          result: new Promise((resolve) => {
+            resolveExecutionPromise = resolve;
+          }),
+        });
+      });
+
+      const { result } = renderProcessorHook();
+
+      await act(async () => {
+        result.current.handleShellCommand('top', new AbortController().signal);
+      });
+
+      expect(result.current.activeShellPtyId).toBe(555);
+
+      act(() => {
+        result.current.backgroundCurrentShell();
+      });
+
+      expect(mockShellBackground).toHaveBeenCalledWith(555);
+      // The actual state update happens when the promise resolves with backgrounded: true
+      // which is handled in handleShellCommand's .then block.
+      // We simulate that here:
+
+      await act(async () => {
+        resolveExecutionPromise(
+          createMockServiceResult({
+            backgrounded: true,
+            pid: 555,
+            output: 'running...',
+          }),
+        );
+      });
+      // Wait for promise resolution
+      await act(async () => await onExecMock.mock.calls[0][0]);
+
+      expect(result.current.backgroundShellCount).toBe(1);
+      expect(result.current.activeShellPtyId).toBeNull();
+    });
+
+    it('should persist background shell on successful exit and mark as exited', async () => {
+      const { result } = renderProcessorHook();
+
+      act(() => {
+        result.current.registerBackgroundShell(888, 'auto-exit', '');
+      });
+
+      // Find the exit callback registered
+      const exitCallback = mockShellOnExit.mock.calls.find(
+        (call) => call[0] === 888,
+      )?.[1];
+      expect(exitCallback).toBeDefined();
+
+      if (exitCallback) {
+        act(() => {
+          exitCallback(0);
+        });
+      }
+
+      // Should NOT be removed, but updated
+      expect(result.current.backgroundShellCount).toBe(0); // Badge count is 0
+      expect(result.current.backgroundShells.has(888)).toBe(true); // Map has it
+      const shell = result.current.backgroundShells.get(888);
+      expect(shell?.status).toBe('exited');
+      expect(shell?.exitCode).toBe(0);
+    });
+
+    it('should persist background shell on failed exit', async () => {
+      const { result } = renderProcessorHook();
+
+      act(() => {
+        result.current.registerBackgroundShell(999, 'fail-exit', '');
+      });
+
+      const exitCallback = mockShellOnExit.mock.calls.find(
+        (call) => call[0] === 999,
+      )?.[1];
+      expect(exitCallback).toBeDefined();
+
+      if (exitCallback) {
+        act(() => {
+          exitCallback(1);
+        });
+      }
+
+      // Should NOT be removed, but updated
+      expect(result.current.backgroundShellCount).toBe(0); // Badge count is 0
+      const shell = result.current.backgroundShells.get(999);
+      expect(shell?.status).toBe('exited');
+      expect(shell?.exitCode).toBe(1);
+
+      // Now dismiss it
+      act(() => {
+        result.current.dismissBackgroundShell(999);
+      });
+      expect(result.current.backgroundShellCount).toBe(0);
+    });
+
+    it('should NOT trigger re-render on background shell output when visible', async () => {
+      const { result, getRenderCount } = renderProcessorHook();
+
+      act(() => {
+        result.current.registerBackgroundShell(1001, 'bg-cmd', 'initial');
+      });
+
+      // Show the background shells
+      act(() => {
+        result.current.toggleBackgroundShell();
+      });
+
+      const initialRenderCount = getRenderCount();
+
+      const subscribeCallback = mockShellSubscribe.mock.calls.find(
+        (call) => call[0] === 1001,
+      )?.[1];
+      expect(subscribeCallback).toBeDefined();
+
+      if (subscribeCallback) {
+        act(() => {
+          subscribeCallback({ type: 'data', chunk: ' + updated' });
+        });
+      }
+
+      expect(getRenderCount()).toBeGreaterThan(initialRenderCount);
+      const shell = result.current.backgroundShells.get(1001);
+      expect(shell?.output).toBe('initial + updated');
+    });
+
+    it('should NOT trigger re-render on background shell output when hidden', async () => {
+      const { result, getRenderCount } = renderProcessorHook();
+
+      act(() => {
+        result.current.registerBackgroundShell(1001, 'bg-cmd', 'initial');
+      });
+
+      // Ensure background shells are hidden (default)
+      const initialRenderCount = getRenderCount();
+
+      const subscribeCallback = mockShellSubscribe.mock.calls.find(
+        (call) => call[0] === 1001,
+      )?.[1];
+      expect(subscribeCallback).toBeDefined();
+
+      if (subscribeCallback) {
+        act(() => {
+          subscribeCallback({ type: 'data', chunk: ' + updated' });
+        });
+      }
+
+      expect(getRenderCount()).toBeGreaterThan(initialRenderCount);
+      const shell = result.current.backgroundShells.get(1001);
+      expect(shell?.output).toBe('initial + updated');
+    });
+
+    it('should trigger re-render on binary progress when visible', async () => {
+      const { result, getRenderCount } = renderProcessorHook();
+
+      act(() => {
+        result.current.registerBackgroundShell(1001, 'bg-cmd', 'initial');
+      });
+
+      // Show the background shells
+      act(() => {
+        result.current.toggleBackgroundShell();
+      });
+
+      const initialRenderCount = getRenderCount();
+
+      const subscribeCallback = mockShellSubscribe.mock.calls.find(
+        (call) => call[0] === 1001,
+      )?.[1];
+      expect(subscribeCallback).toBeDefined();
+
+      if (subscribeCallback) {
+        act(() => {
+          subscribeCallback({ type: 'binary_progress', bytesReceived: 1024 });
+        });
+      }
+
+      expect(getRenderCount()).toBeGreaterThan(initialRenderCount);
+      const shell = result.current.backgroundShells.get(1001);
+      expect(shell?.isBinary).toBe(true);
+      expect(shell?.binaryBytesReceived).toBe(1024);
+    });
+
+    it('should NOT hide background shell when model is responding without confirmation', async () => {
+      const { result, rerender } = renderProcessorHook();
+
+      // 1. Register and show background shell
+      act(() => {
+        result.current.registerBackgroundShell(1001, 'bg-cmd', 'initial');
+      });
+      act(() => {
+        result.current.toggleBackgroundShell();
+      });
+      expect(result.current.isBackgroundShellVisible).toBe(true);
+
+      // 2. Simulate model responding (not waiting for confirmation)
+      act(() => {
+        rerender(false); // isWaitingForConfirmation = false
+      });
+
+      // Should stay visible
+      expect(result.current.isBackgroundShellVisible).toBe(true);
+    });
+
+    it('should hide background shell when waiting for confirmation and restore after delay', async () => {
+      const { result, rerender } = renderProcessorHook();
+
+      // 1. Register and show background shell
+      act(() => {
+        result.current.registerBackgroundShell(1001, 'bg-cmd', 'initial');
+      });
+      act(() => {
+        result.current.toggleBackgroundShell();
+      });
+      expect(result.current.isBackgroundShellVisible).toBe(true);
+
+      // 2. Simulate tool confirmation showing up
+      act(() => {
+        rerender(true); // isWaitingForConfirmation = true
+      });
+
+      // Should be hidden
+      expect(result.current.isBackgroundShellVisible).toBe(false);
+
+      // 3. Simulate confirmation accepted (waiting for PTY start)
+      act(() => {
+        rerender(false);
+      });
+
+      // Should STAY hidden during the 300ms gap
+      expect(result.current.isBackgroundShellVisible).toBe(false);
+
+      // 4. Wait for restore delay
+      await waitFor(() =>
+        expect(result.current.isBackgroundShellVisible).toBe(true),
+      );
+    });
+
+    it('should auto-hide background shell when foreground shell starts and restore when it ends', async () => {
+      const { result } = renderProcessorHook();
+
+      // 1. Register and show background shell
+      act(() => {
+        result.current.registerBackgroundShell(1001, 'bg-cmd', 'initial');
+      });
+      act(() => {
+        result.current.toggleBackgroundShell();
+      });
+      expect(result.current.isBackgroundShellVisible).toBe(true);
+
+      // 2. Start foreground shell
+      act(() => {
+        result.current.handleShellCommand('ls', new AbortController().signal);
+      });
+
+      // Wait for PID to be set
+      await waitFor(() => expect(result.current.activeShellPtyId).toBe(12345));
+
+      // Should be hidden automatically
+      expect(result.current.isBackgroundShellVisible).toBe(false);
+
+      // 3. Complete foreground shell
+      act(() => {
+        resolveExecutionPromise(createMockServiceResult());
+      });
+
+      await waitFor(() => expect(result.current.activeShellPtyId).toBe(null));
+
+      // Should be restored automatically (after delay)
+      await waitFor(() =>
+        expect(result.current.isBackgroundShellVisible).toBe(true),
+      );
+    });
+
+    it('should NOT restore background shell if it was manually hidden during foreground execution', async () => {
+      const { result } = renderProcessorHook();
+
+      // 1. Register and show background shell
+      act(() => {
+        result.current.registerBackgroundShell(1001, 'bg-cmd', 'initial');
+      });
+      act(() => {
+        result.current.toggleBackgroundShell();
+      });
+      expect(result.current.isBackgroundShellVisible).toBe(true);
+
+      // 2. Start foreground shell
+      act(() => {
+        result.current.handleShellCommand('ls', new AbortController().signal);
+      });
+      await waitFor(() => expect(result.current.activeShellPtyId).toBe(12345));
+      expect(result.current.isBackgroundShellVisible).toBe(false);
+
+      // 3. Manually toggle visibility (e.g. user wants to peek)
+      act(() => {
+        result.current.toggleBackgroundShell();
+      });
+      expect(result.current.isBackgroundShellVisible).toBe(true);
+
+      // 4. Complete foreground shell
+      act(() => {
+        resolveExecutionPromise(createMockServiceResult());
+      });
+      await waitFor(() => expect(result.current.activeShellPtyId).toBe(null));
+
+      // It should NOT change visibility because manual toggle cleared the auto-restore flag
+      // After delay it should stay true (as it was manually toggled to true)
+      await waitFor(() =>
+        expect(result.current.isBackgroundShellVisible).toBe(true),
+      );
+    });
+  });
 });

packages/cli/src/ui/hooks/shellCommandProcessor.ts

@@ -9,13 +9,8 @@ import type {
   IndividualToolCallDisplay,
 } from '../types.js';
 import { ToolCallStatus } from '../types.js';
-import { useCallback, useState } from 'react';
-import type {
-  AnsiOutput,
-  Config,
-  GeminiClient,
-  ShellExecutionResult,
-} from '@google/gemini-cli-core';
+import { useCallback, useReducer, useRef, useEffect } from 'react';
+import type { AnsiOutput, Config, GeminiClient } from '@google/gemini-cli-core';
 import { isBinary, ShellExecutionService } from '@google/gemini-cli-core';
 import { type PartListUnion } from '@google/genai';
 import type { UseHistoryManagerReturn } from './useHistoryManager.js';
@@ -26,8 +21,15 @@ import path from 'node:path';
 import os from 'node:os';
 import fs from 'node:fs';
 import { themeManager } from '../../ui/themes/theme-manager.js';
+import {
+  shellReducer,
+  initialState,
+  type BackgroundShell,
+} from './shellReducer.js';
+export { type BackgroundShell };
 
 export const OUTPUT_UPDATE_INTERVAL_MS = 1000;
+const RESTORE_VISIBILITY_DELAY_MS = 300;
 const MAX_OUTPUT_LENGTH = 10000;
 
 function addShellCommandToGeminiHistory(
@@ -75,9 +77,190 @@ export const useShellCommandProcessor = (
   setShellInputFocused: (value: boolean) => void,
   terminalWidth?: number,
   terminalHeight?: number,
+  activeToolPtyId?: number,
+  isWaitingForConfirmation?: boolean,
 ) => {
-  const [activeShellPtyId, setActiveShellPtyId] = useState<number | null>(null);
-  const [lastShellOutputTime, setLastShellOutputTime] = useState<number>(0);
+  const [state, dispatch] = useReducer(shellReducer, initialState);
+
+  // Consolidate stable tracking into a single manager object
+  const manager = useRef<{
+    wasVisibleBeforeForeground: boolean;
+    restoreTimeout: NodeJS.Timeout | null;
+    backgroundedPids: Set<number>;
+    subscriptions: Map<number, () => void>;
+  } | null>(null);
+
+  if (!manager.current) {
+    manager.current = {
+      wasVisibleBeforeForeground: false,
+      restoreTimeout: null,
+      backgroundedPids: new Set(),
+      subscriptions: new Map(),
+    };
+  }
+  const m = manager.current;
+
+  const activePtyId = state.activeShellPtyId || activeToolPtyId;
+
+  useEffect(() => {
+    const isForegroundActive = !!activePtyId || !!isWaitingForConfirmation;
+
+    if (isForegroundActive) {
+      if (m.restoreTimeout) {
+        clearTimeout(m.restoreTimeout);
+        m.restoreTimeout = null;
+      }
+
+      if (state.isBackgroundShellVisible && !m.wasVisibleBeforeForeground) {
+        m.wasVisibleBeforeForeground = true;
+        dispatch({ type: 'SET_VISIBILITY', visible: false });
+      }
+    } else if (m.wasVisibleBeforeForeground && !m.restoreTimeout) {
+      // Restore if it was automatically hidden, with a small delay to avoid
+      // flickering between model turn segments.
+      m.restoreTimeout = setTimeout(() => {
+        dispatch({ type: 'SET_VISIBILITY', visible: true });
+        m.wasVisibleBeforeForeground = false;
+        m.restoreTimeout = null;
+      }, RESTORE_VISIBILITY_DELAY_MS);
+    }
+
+    return () => {
+      if (m.restoreTimeout) {
+        clearTimeout(m.restoreTimeout);
+      }
+    };
+  }, [
+    activePtyId,
+    isWaitingForConfirmation,
+    state.isBackgroundShellVisible,
+    m,
+    dispatch,
+  ]);
+
+  useEffect(
+    () => () => {
+      // Unsubscribe from all background shell events on unmount
+      for (const unsubscribe of m.subscriptions.values()) {
+        unsubscribe();
+      }
+      m.subscriptions.clear();
+    },
+    [m],
+  );
+
+  const toggleBackgroundShell = useCallback(() => {
+    if (state.backgroundShells.size > 0) {
+      const willBeVisible = !state.isBackgroundShellVisible;
+      dispatch({ type: 'TOGGLE_VISIBILITY' });
+
+      const isForegroundActive = !!activePtyId || !!isWaitingForConfirmation;
+      // If we are manually showing it during foreground, we set the restore flag
+      // so that useEffect doesn't immediately hide it again.
+      // If we are manually hiding it, we clear the restore flag so it stays hidden.
+      if (willBeVisible && isForegroundActive) {
+        m.wasVisibleBeforeForeground = true;
+      } else {
+        m.wasVisibleBeforeForeground = false;
+      }
+
+      if (willBeVisible) {
+        dispatch({ type: 'SYNC_BACKGROUND_SHELLS' });
+      }
+    } else {
+      dispatch({ type: 'SET_VISIBILITY', visible: false });
+      addItemToHistory(
+        {
+          type: 'info',
+          text: 'No background shells are currently active.',
+        },
+        Date.now(),
+      );
+    }
+  }, [
+    addItemToHistory,
+    state.backgroundShells.size,
+    state.isBackgroundShellVisible,
+    activePtyId,
+    isWaitingForConfirmation,
+    m,
+    dispatch,
+  ]);
+
+  const backgroundCurrentShell = useCallback(() => {
+    const pidToBackground = state.activeShellPtyId || activeToolPtyId;
+    if (pidToBackground) {
+      ShellExecutionService.background(pidToBackground);
+      m.backgroundedPids.add(pidToBackground);
+      // Ensure backgrounding is silent and doesn't trigger restoration
+      m.wasVisibleBeforeForeground = false;
+      if (m.restoreTimeout) {
+        clearTimeout(m.restoreTimeout);
+        m.restoreTimeout = null;
+      }
+    }
+  }, [state.activeShellPtyId, activeToolPtyId, m]);
+
+  const dismissBackgroundShell = useCallback(
+    (pid: number) => {
+      const shell = state.backgroundShells.get(pid);
+      if (shell) {
+        if (shell.status === 'running') {
+          ShellExecutionService.kill(pid);
+        }
+        dispatch({ type: 'DISMISS_SHELL', pid });
+        m.backgroundedPids.delete(pid);
+
+        // Unsubscribe from updates
+        const unsubscribe = m.subscriptions.get(pid);
+        if (unsubscribe) {
+          unsubscribe();
+          m.subscriptions.delete(pid);
+        }
+      }
+    },
+    [state.backgroundShells, dispatch, m],
+  );
+
+  const registerBackgroundShell = useCallback(
+    (pid: number, command: string, initialOutput: string | AnsiOutput) => {
+      dispatch({ type: 'REGISTER_SHELL', pid, command, initialOutput });
+
+      // Subscribe to process exit directly
+      const exitUnsubscribe = ShellExecutionService.onExit(pid, (code) => {
+        dispatch({
+          type: 'UPDATE_SHELL',
+          pid,
+          update: { status: 'exited', exitCode: code },
+        });
+        m.backgroundedPids.delete(pid);
+      });
+
+      // Subscribe to future updates (data only)
+      const dataUnsubscribe = ShellExecutionService.subscribe(pid, (event) => {
+        if (event.type === 'data') {
+          dispatch({ type: 'APPEND_SHELL_OUTPUT', pid, chunk: event.chunk });
+        } else if (event.type === 'binary_detected') {
+          dispatch({ type: 'UPDATE_SHELL', pid, update: { isBinary: true } });
+        } else if (event.type === 'binary_progress') {
+          dispatch({
+            type: 'UPDATE_SHELL',
+            pid,
+            update: {
+              isBinary: true,
+              binaryBytesReceived: event.bytesReceived,
+            },
+          });
+        }
+      });
+
+      m.subscriptions.set(pid, () => {
+        exitUnsubscribe();
+        dataUnsubscribe();
+      });
+    },
+    [dispatch, m],
+  );
 
   const handleShellCommand = useCallback(
     (rawQuery: PartListUnion, abortSignal: AbortSignal): boolean => {
@@ -109,9 +292,7 @@ export const useShellCommandProcessor = (
         commandToExecute = `{ ${command} }; __code=$?; pwd > "${pwdFilePath}"; exit $__code`;
       }
 
-      const executeCommand = async (
-        resolve: (value: void | PromiseLike<void>) => void,
-      ) => {
+      const executeCommand = async () => {
         let cumulativeStdout: string | AnsiOutput = '';
         let isBinaryStream = false;
         let binaryBytesReceived = 0;
@@ -151,84 +332,90 @@ export const useShellCommandProcessor = (
             defaultBg: activeTheme.colors.Background,
           };
 
-          const { pid, result } = await ShellExecutionService.execute(
-            commandToExecute,
-            targetDir,
-            (event) => {
-              let shouldUpdate = false;
-              switch (event.type) {
-                case 'data':
-                  // Do not process text data if we've already switched to binary mode.
-                  if (isBinaryStream) break;
-                  // PTY provides the full screen state, so we just replace.
-                  // Child process provides chunks, so we append.
-                  if (config.getEnableInteractiveShell()) {
-                    cumulativeStdout = event.chunk;
-                    shouldUpdate = true;
-                  } else if (
-                    typeof event.chunk === 'string' &&
-                    typeof cumulativeStdout === 'string'
-                  ) {
-                    cumulativeStdout += event.chunk;
-                    shouldUpdate = true;
-                  }
-                  break;
-                case 'binary_detected':
-                  isBinaryStream = true;
-                  // Force an immediate UI update to show the binary detection message.
-                  shouldUpdate = true;
-                  break;
-                case 'binary_progress':
-                  isBinaryStream = true;
-                  binaryBytesReceived = event.bytesReceived;
-                  shouldUpdate = true;
-                  break;
-                default: {
-                  throw new Error('An unhandled ShellOutputEvent was found.');
-                }
-              }
+          const { pid, result: resultPromise } =
+            await ShellExecutionService.execute(
+              commandToExecute,
+              targetDir,
+              (event) => {
+                let shouldUpdate = false;
 
-              // Compute the display string based on the *current* state.
-              let currentDisplayOutput: string | AnsiOutput;
-              if (isBinaryStream) {
-                if (binaryBytesReceived > 0) {
-                  currentDisplayOutput = `[Receiving binary output... ${formatBytes(
-                    binaryBytesReceived,
-                  )} received]`;
-                } else {
+                switch (event.type) {
+                  case 'data':
+                    if (isBinaryStream) break;
+                    if (typeof event.chunk === 'string') {
+                      if (typeof cumulativeStdout === 'string') {
+                        cumulativeStdout += event.chunk;
+                      } else {
+                        cumulativeStdout = event.chunk;
+                      }
+                    } else {
+                      // AnsiOutput (PTY) is always the full state
+                      cumulativeStdout = event.chunk;
+                    }
+                    shouldUpdate = true;
+                    break;
+                  case 'binary_detected':
+                    isBinaryStream = true;
+                    shouldUpdate = true;
+                    break;
+                  case 'binary_progress':
+                    isBinaryStream = true;
+                    binaryBytesReceived = event.bytesReceived;
+                    shouldUpdate = true;
+                    break;
+                  case 'exit':
+                    // No action needed for exit event during streaming
+                    break;
+                  default:
+                    throw new Error('An unhandled ShellOutputEvent was found.');
+                }
+
+                if (executionPid && m.backgroundedPids.has(executionPid)) {
+                  // If already backgrounded, let the background shell subscription handle it.
+                  dispatch({
+                    type: 'APPEND_SHELL_OUTPUT',
+                    pid: executionPid,
+                    chunk:
+                      event.type === 'data' ? event.chunk : cumulativeStdout,
+                  });
+                  return;
+                }
+
+                let currentDisplayOutput: string | AnsiOutput;
+                if (isBinaryStream) {
                   currentDisplayOutput =
-                    '[Binary output detected. Halting stream...]';
+                    binaryBytesReceived > 0
+                      ? `[Receiving binary output... ${formatBytes(binaryBytesReceived)} received]`
+                      : '[Binary output detected. Halting stream...]';
+                } else {
+                  currentDisplayOutput = cumulativeStdout;
                 }
-              } else {
-                currentDisplayOutput = cumulativeStdout;
-              }
 
-              // Throttle pending UI updates, but allow forced updates.
-              if (shouldUpdate) {
-                setLastShellOutputTime(Date.now());
-                setPendingHistoryItem((prevItem) => {
-                  if (prevItem?.type === 'tool_group') {
-                    return {
-                      ...prevItem,
-                      tools: prevItem.tools.map((tool) =>
-                        tool.callId === callId
-                          ? { ...tool, resultDisplay: currentDisplayOutput }
-                          : tool,
-                      ),
-                    };
-                  }
-                  return prevItem;
-                });
-              }
-            },
-            abortSignal,
-            config.getEnableInteractiveShell(),
-            shellExecutionConfig,
-          );
+                if (shouldUpdate) {
+                  dispatch({ type: 'SET_OUTPUT_TIME', time: Date.now() });
+                  setPendingHistoryItem((prevItem) => {
+                    if (prevItem?.type === 'tool_group') {
+                      return {
+                        ...prevItem,
+                        tools: prevItem.tools.map((tool) =>
+                          tool.callId === callId
+                            ? { ...tool, resultDisplay: currentDisplayOutput }
+                            : tool,
+                        ),
+                      };
+                    }
+                    return prevItem;
+                  });
+                }
+              },
+              abortSignal,
+              config.getEnableInteractiveShell(),
+              shellExecutionConfig,
+            );
 
           executionPid = pid;
           if (pid) {
-            setActiveShellPtyId(pid);
+            dispatch({ type: 'SET_ACTIVE_PTY', pid });
             setPendingHistoryItem((prevItem) => {
               if (prevItem?.type === 'tool_group') {
                 return {
@@ -242,94 +429,69 @@ export const useShellCommandProcessor = (
             });
           }
 
-          result
-            .then((result: ShellExecutionResult) => {
-              setPendingHistoryItem(null);
+          const result = await resultPromise;
+          setPendingHistoryItem(null);
 
-              let mainContent: string;
+          if (result.backgrounded && result.pid) {
+            registerBackgroundShell(result.pid, rawQuery, cumulativeStdout);
+            dispatch({ type: 'SET_ACTIVE_PTY', pid: null });
+          }
 
-              if (isBinary(result.rawOutput)) {
-                mainContent =
-                  '[Command produced binary output, which is not shown.]';
-              } else {
-                mainContent =
-                  result.output.trim() || '(Command produced no output)';
-              }
+          let mainContent: string;
+          if (isBinary(result.rawOutput)) {
+            mainContent =
+              '[Command produced binary output, which is not shown.]';
+          } else {
+            mainContent =
+              result.output.trim() || '(Command produced no output)';
+          }
 
-              let finalOutput = mainContent;
-              let finalStatus = ToolCallStatus.Success;
+          let finalOutput = mainContent;
+          let finalStatus = ToolCallStatus.Success;
 
-              if (result.error) {
-                finalStatus = ToolCallStatus.Error;
-                finalOutput = `${result.error.message}\n${finalOutput}`;
-              } else if (result.aborted) {
-                finalStatus = ToolCallStatus.Canceled;
-                finalOutput = `Command was cancelled.\n${finalOutput}`;
-              } else if (result.signal) {
-                finalStatus = ToolCallStatus.Error;
-                finalOutput = `Command terminated by signal: ${result.signal}.\n${finalOutput}`;
-              } else if (result.exitCode !== 0) {
-                finalStatus = ToolCallStatus.Error;
-                finalOutput = `Command exited with code ${result.exitCode}.\n${finalOutput}`;
-              }
+          if (result.error) {
+            finalStatus = ToolCallStatus.Error;
+            finalOutput = `${result.error.message}\n${finalOutput}`;
+          } else if (result.aborted) {
+            finalStatus = ToolCallStatus.Canceled;
+            finalOutput = `Command was cancelled.\n${finalOutput}`;
+          } else if (result.backgrounded) {
+            finalStatus = ToolCallStatus.Success;
+            finalOutput = `Command moved to background (PID: ${result.pid}). Output hidden. Press Ctrl+B to view.`;
+          } else if (result.signal) {
+            finalStatus = ToolCallStatus.Error;
+            finalOutput = `Command terminated by signal: ${result.signal}.\n${finalOutput}`;
+          } else if (result.exitCode !== 0) {
+            finalStatus = ToolCallStatus.Error;
+            finalOutput = `Command exited with code ${result.exitCode}.\n${finalOutput}`;
+          }
 
-              if (pwdFilePath && fs.existsSync(pwdFilePath)) {
-                const finalPwd = fs.readFileSync(pwdFilePath, 'utf8').trim();
-                if (finalPwd && finalPwd !== targetDir) {
-                  const warning = `WARNING: shell mode is stateless; the directory change to '${finalPwd}' will not persist.`;
-                  finalOutput = `${warning}\n\n${finalOutput}`;
-                }
-              }
+          if (pwdFilePath && fs.existsSync(pwdFilePath)) {
+            const finalPwd = fs.readFileSync(pwdFilePath, 'utf8').trim();
+            if (finalPwd && finalPwd !== targetDir) {
+              const warning = `WARNING: shell mode is stateless; the directory change to '${finalPwd}' will not persist.`;
+              finalOutput = `${warning}\n\n${finalOutput}`;
+            }
+          }
 
-              const finalToolDisplay: IndividualToolCallDisplay = {
-                ...initialToolDisplay,
-                status: finalStatus,
-                resultDisplay: finalOutput,
-              };
+          const finalToolDisplay: IndividualToolCallDisplay = {
+            ...initialToolDisplay,
+            status: finalStatus,
+            resultDisplay: finalOutput,
+          };
 
-              // Add the complete, contextual result to the local UI history.
-              // We skip this for cancelled commands because useGeminiStream handles the
-              // immediate addition of the cancelled item to history to prevent flickering/duplicates.
-              if (finalStatus !== ToolCallStatus.Canceled) {
-                addItemToHistory(
-                  {
-                    type: 'tool_group',
-                    tools: [finalToolDisplay],
-                  } as HistoryItemWithoutId,
-                  userMessageTimestamp,
-                );
-              }
+          if (finalStatus !== ToolCallStatus.Canceled) {
+            addItemToHistory(
+              {
+                type: 'tool_group',
+                tools: [finalToolDisplay],
+              } as HistoryItemWithoutId,
+              userMessageTimestamp,
+            );
+          }
 
-              // Add the same complete, contextual result to the LLM's history.
-              addShellCommandToGeminiHistory(
-                geminiClient,
-                rawQuery,
-                finalOutput,
-              );
-            })
-            .catch((err) => {
-              setPendingHistoryItem(null);
-              const errorMessage =
-                err instanceof Error ? err.message : String(err);
-              addItemToHistory(
-                {
-                  type: 'error',
-                  text: `An unexpected error occurred: ${errorMessage}`,
-                },
-                userMessageTimestamp,
-              );
-            })
-            .finally(() => {
-              abortSignal.removeEventListener('abort', abortHandler);
-              if (pwdFilePath && fs.existsSync(pwdFilePath)) {
-                fs.unlinkSync(pwdFilePath);
-              }
-              setActiveShellPtyId(null);
-              setShellInputFocused(false);
-              resolve();
-            });
+          addShellCommandToGeminiHistory(geminiClient, rawQuery, finalOutput);
         } catch (err) {
-          // This block handles synchronous errors from `execute`
           setPendingHistoryItem(null);
           const errorMessage = err instanceof Error ? err.message : String(err);
           addItemToHistory(
@@ -339,23 +501,18 @@ export const useShellCommandProcessor = (
             },
             userMessageTimestamp,
           );
-
-          // Perform cleanup here as well
+        } finally {
+          abortSignal.removeEventListener('abort', abortHandler);
           if (pwdFilePath && fs.existsSync(pwdFilePath)) {
             fs.unlinkSync(pwdFilePath);
           }
-          setActiveShellPtyId(null);
+
+          dispatch({ type: 'SET_ACTIVE_PTY', pid: null });
           setShellInputFocused(false);
-          resolve(); // Resolve the promise to unblock `onExec`
         }
       };
 
-      const execPromise = new Promise<void>((resolve) => {
-        // eslint-disable-next-line @typescript-eslint/no-floating-promises
-        executeCommand(resolve);
-      });
-
-      onExec(execPromise);
+      onExec(executeCommand());
       return true;
     },
     [
@@ -368,8 +525,26 @@ export const useShellCommandProcessor = (
       setShellInputFocused,
       terminalHeight,
       terminalWidth,
+      registerBackgroundShell,
+      m,
+      dispatch,
     ],
   );
 
-  return { handleShellCommand, activeShellPtyId, lastShellOutputTime };
+  const backgroundShellCount = Array.from(
+    state.backgroundShells.values(),
+  ).filter((s: BackgroundShell) => s.status === 'running').length;
+
+  return {
+    handleShellCommand,
+    activeShellPtyId: state.activeShellPtyId,
+    lastShellOutputTime: state.lastShellOutputTime,
+    backgroundShellCount,
+    isBackgroundShellVisible: state.isBackgroundShellVisible,
+    toggleBackgroundShell,
+    backgroundCurrentShell,
+    registerBackgroundShell,
+    dismissBackgroundShell,
+    backgroundShells: state.backgroundShells,
+  };
 };

packages/cli/src/ui/hooks/shellReducer.test.ts

@@ -0,0 +1,193 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { describe, it, expect } from 'vitest';
+import {
+  shellReducer,
+  initialState,
+  type ShellState,
+  type ShellAction,
+} from './shellReducer.js';
+
+describe('shellReducer', () => {
+  it('should return the initial state', () => {
+    // @ts-expect-error - testing default case
+    expect(shellReducer(initialState, { type: 'UNKNOWN' })).toEqual(
+      initialState,
+    );
+  });
+
+  it('should handle SET_ACTIVE_PTY', () => {
+    const action: ShellAction = { type: 'SET_ACTIVE_PTY', pid: 12345 };
+    const state = shellReducer(initialState, action);
+    expect(state.activeShellPtyId).toBe(12345);
+  });
+
+  it('should handle SET_OUTPUT_TIME', () => {
+    const now = Date.now();
+    const action: ShellAction = { type: 'SET_OUTPUT_TIME', time: now };
+    const state = shellReducer(initialState, action);
+    expect(state.lastShellOutputTime).toBe(now);
+  });
+
+  it('should handle SET_VISIBILITY', () => {
+    const action: ShellAction = { type: 'SET_VISIBILITY', visible: true };
+    const state = shellReducer(initialState, action);
+    expect(state.isBackgroundShellVisible).toBe(true);
+  });
+
+  it('should handle TOGGLE_VISIBILITY', () => {
+    const action: ShellAction = { type: 'TOGGLE_VISIBILITY' };
+    let state = shellReducer(initialState, action);
+    expect(state.isBackgroundShellVisible).toBe(true);
+    state = shellReducer(state, action);
+    expect(state.isBackgroundShellVisible).toBe(false);
+  });
+
+  it('should handle REGISTER_SHELL', () => {
+    const action: ShellAction = {
+      type: 'REGISTER_SHELL',
+      pid: 1001,
+      command: 'ls',
+      initialOutput: 'init',
+    };
+    const state = shellReducer(initialState, action);
+    expect(state.backgroundShells.has(1001)).toBe(true);
+    expect(state.backgroundShells.get(1001)).toEqual({
+      pid: 1001,
+      command: 'ls',
+      output: 'init',
+      isBinary: false,
+      binaryBytesReceived: 0,
+      status: 'running',
+    });
+  });
+
+  it('should not REGISTER_SHELL if PID already exists', () => {
+    const action: ShellAction = {
+      type: 'REGISTER_SHELL',
+      pid: 1001,
+      command: 'ls',
+      initialOutput: 'init',
+    };
+    const state = shellReducer(initialState, action);
+    const state2 = shellReducer(state, { ...action, command: 'other' });
+    expect(state2).toBe(state);
+    expect(state2.backgroundShells.get(1001)?.command).toBe('ls');
+  });
+
+  it('should handle UPDATE_SHELL', () => {
+    const registeredState = shellReducer(initialState, {
+      type: 'REGISTER_SHELL',
+      pid: 1001,
+      command: 'ls',
+      initialOutput: 'init',
+    });
+
+    const action: ShellAction = {
+      type: 'UPDATE_SHELL',
+      pid: 1001,
+      update: { status: 'exited', exitCode: 0 },
+    };
+    const state = shellReducer(registeredState, action);
+    const shell = state.backgroundShells.get(1001);
+    expect(shell?.status).toBe('exited');
+    expect(shell?.exitCode).toBe(0);
+    // Map should be new
+    expect(state.backgroundShells).not.toBe(registeredState.backgroundShells);
+  });
+
+  it('should handle APPEND_SHELL_OUTPUT when visible (triggers re-render)', () => {
+    const visibleState: ShellState = {
+      ...initialState,
+      isBackgroundShellVisible: true,
+      backgroundShells: new Map([
+        [
+          1001,
+          {
+            pid: 1001,
+            command: 'ls',
+            output: 'init',
+            isBinary: false,
+            binaryBytesReceived: 0,
+            status: 'running',
+          },
+        ],
+      ]),
+    };
+
+    const action: ShellAction = {
+      type: 'APPEND_SHELL_OUTPUT',
+      pid: 1001,
+      chunk: ' + more',
+    };
+    const state = shellReducer(visibleState, action);
+    expect(state.backgroundShells.get(1001)?.output).toBe('init + more');
+    // Drawer is visible, so we expect a NEW map object to trigger React re-render
+    expect(state.backgroundShells).not.toBe(visibleState.backgroundShells);
+  });
+
+  it('should handle APPEND_SHELL_OUTPUT when hidden (no re-render optimization)', () => {
+    const hiddenState: ShellState = {
+      ...initialState,
+      isBackgroundShellVisible: false,
+      backgroundShells: new Map([
+        [
+          1001,
+          {
+            pid: 1001,
+            command: 'ls',
+            output: 'init',
+            isBinary: false,
+            binaryBytesReceived: 0,
+            status: 'running',
+          },
+        ],
+      ]),
+    };
+
+    const action: ShellAction = {
+      type: 'APPEND_SHELL_OUTPUT',
+      pid: 1001,
+      chunk: ' + more',
+    };
+    const state = shellReducer(hiddenState, action);
+    expect(state.backgroundShells.get(1001)?.output).toBe('init + more');
+    // Drawer is hidden, so we expect the SAME map object (mutation optimization)
+    expect(state.backgroundShells).toBe(hiddenState.backgroundShells);
+  });
+
+  it('should handle SYNC_BACKGROUND_SHELLS', () => {
+    const action: ShellAction = { type: 'SYNC_BACKGROUND_SHELLS' };
+    const state = shellReducer(initialState, action);
+    expect(state.backgroundShells).not.toBe(initialState.backgroundShells);
+  });
+
+  it('should handle DISMISS_SHELL', () => {
+    const registeredState: ShellState = {
+      ...initialState,
+      isBackgroundShellVisible: true,
+      backgroundShells: new Map([
+        [
+          1001,
+          {
+            pid: 1001,
+            command: 'ls',
+            output: 'init',
+            isBinary: false,
+            binaryBytesReceived: 0,
+            status: 'running',
+          },
+        ],
+      ]),
+    };
+
+    const action: ShellAction = { type: 'DISMISS_SHELL', pid: 1001 };
+    const state = shellReducer(registeredState, action);
+    expect(state.backgroundShells.has(1001)).toBe(false);
+    expect(state.isBackgroundShellVisible).toBe(false); // Auto-hide if last shell
+  });
+});

packages/cli/src/ui/hooks/shellReducer.ts

@@ -0,0 +1,128 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import type { AnsiOutput } from '@google/gemini-cli-core';
+
+export interface BackgroundShell {
+  pid: number;
+  command: string;
+  output: string | AnsiOutput;
+  isBinary: boolean;
+  binaryBytesReceived: number;
+  status: 'running' | 'exited';
+  exitCode?: number;
+}
+
+export interface ShellState {
+  activeShellPtyId: number | null;
+  lastShellOutputTime: number;
+  backgroundShells: Map<number, BackgroundShell>;
+  isBackgroundShellVisible: boolean;
+}
+
+export type ShellAction =
+  | { type: 'SET_ACTIVE_PTY'; pid: number | null }
+  | { type: 'SET_OUTPUT_TIME'; time: number }
+  | { type: 'SET_VISIBILITY'; visible: boolean }
+  | { type: 'TOGGLE_VISIBILITY' }
+  | {
+      type: 'REGISTER_SHELL';
+      pid: number;
+      command: string;
+      initialOutput: string | AnsiOutput;
+    }
+  | { type: 'UPDATE_SHELL'; pid: number; update: Partial<BackgroundShell> }
+  | { type: 'APPEND_SHELL_OUTPUT'; pid: number; chunk: string | AnsiOutput }
+  | { type: 'SYNC_BACKGROUND_SHELLS' }
+  | { type: 'DISMISS_SHELL'; pid: number };
+
+export const initialState: ShellState = {
+  activeShellPtyId: null,
+  lastShellOutputTime: 0,
+  backgroundShells: new Map(),
+  isBackgroundShellVisible: false,
+};
+
+export function shellReducer(
+  state: ShellState,
+  action: ShellAction,
+): ShellState {
+  switch (action.type) {
+    case 'SET_ACTIVE_PTY':
+      return { ...state, activeShellPtyId: action.pid };
+    case 'SET_OUTPUT_TIME':
+      return { ...state, lastShellOutputTime: action.time };
+    case 'SET_VISIBILITY':
+      return { ...state, isBackgroundShellVisible: action.visible };
+    case 'TOGGLE_VISIBILITY':
+      return {
+        ...state,
+        isBackgroundShellVisible: !state.isBackgroundShellVisible,
+      };
+    case 'REGISTER_SHELL': {
+      if (state.backgroundShells.has(action.pid)) return state;
+      const nextShells = new Map(state.backgroundShells);
+      nextShells.set(action.pid, {
+        pid: action.pid,
+        command: action.command,
+        output: action.initialOutput,
+        isBinary: false,
+        binaryBytesReceived: 0,
+        status: 'running',
+      });
+      return { ...state, backgroundShells: nextShells };
+    }
+    case 'UPDATE_SHELL': {
+      const shell = state.backgroundShells.get(action.pid);
+      if (!shell) return state;
+      const nextShells = new Map(state.backgroundShells);
+      const updatedShell = { ...shell, ...action.update };
+      // Maintain insertion order, move to end if status changed to exited
+      if (action.update.status === 'exited') {
+        nextShells.delete(action.pid);
+      }
+      nextShells.set(action.pid, updatedShell);
+      return { ...state, backgroundShells: nextShells };
+    }
+    case 'APPEND_SHELL_OUTPUT': {
+      const shell = state.backgroundShells.get(action.pid);
+      if (!shell) return state;
+      // Note: we mutate the shell object in the map for background updates
+      // to avoid re-rendering if the drawer is not visible.
+      // This is an intentional performance optimization for the CLI.
+      let newOutput = shell.output;
+      if (typeof action.chunk === 'string') {
+        newOutput =
+          typeof shell.output === 'string'
+            ? shell.output + action.chunk
+            : action.chunk;
+      } else {
+        newOutput = action.chunk;
+      }
+      shell.output = newOutput;
+
+      if (state.isBackgroundShellVisible) {
+        return { ...state, backgroundShells: new Map(state.backgroundShells) };
+      }
+      return state;
+    }
+    case 'SYNC_BACKGROUND_SHELLS': {
+      return { ...state, backgroundShells: new Map(state.backgroundShells) };
+    }
+    case 'DISMISS_SHELL': {
+      const nextShells = new Map(state.backgroundShells);
+      nextShells.delete(action.pid);
+      return {
+        ...state,
+        backgroundShells: nextShells,
+        isBackgroundShellVisible:
+          nextShells.size === 0 ? false : state.isBackgroundShellVisible,
+      };
+    }
+    default:
+      return state;
+  }
+}

packages/cli/src/ui/hooks/slashCommandProcessor.test.tsx

@@ -213,6 +213,7 @@ describe('useSlashCommandProcessor', () => {
             toggleDebugProfiler: vi.fn(),
             dispatchExtensionStateUpdate: vi.fn(),
             addConfirmUpdateExtensionRequest: vi.fn(),
+            toggleBackgroundShell: vi.fn(),
             setText: vi.fn(),
           },
           new Map(), // extensionsUpdateState

packages/cli/src/ui/hooks/slashCommandProcessor.ts

@@ -82,6 +82,7 @@ interface SlashCommandProcessorActions {
   toggleDebugProfiler: () => void;
   dispatchExtensionStateUpdate: (action: ExtensionUpdateAction) => void;
   addConfirmUpdateExtensionRequest: (request: ConfirmationRequest) => void;
+  toggleBackgroundShell: () => void;
   setText: (text: string) => void;
 }
 
@@ -237,6 +238,7 @@ export const useSlashCommandProcessor = (
         addConfirmUpdateExtensionRequest:
           actions.addConfirmUpdateExtensionRequest,
         removeComponent: () => setCustomDialog(null),
+        toggleBackgroundShell: actions.toggleBackgroundShell,
       },
       session: {
         stats: session.stats,

packages/cli/src/ui/hooks/useBackgroundShellManager.test.tsx

@@ -0,0 +1,191 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { render } from '../../test-utils/render.js';
+import {
+  useBackgroundShellManager,
+  type BackgroundShellManagerProps,
+} from './useBackgroundShellManager.js';
+import { describe, it, expect, vi, beforeEach } from 'vitest';
+import { act } from 'react';
+import { type BackgroundShell } from './shellReducer.js';
+
+describe('useBackgroundShellManager', () => {
+  const setEmbeddedShellFocused = vi.fn();
+  const terminalHeight = 30;
+
+  beforeEach(() => {
+    vi.clearAllMocks();
+  });
+
+  const renderHook = (props: BackgroundShellManagerProps) => {
+    let hookResult: ReturnType<typeof useBackgroundShellManager>;
+    function TestComponent({ p }: { p: BackgroundShellManagerProps }) {
+      hookResult = useBackgroundShellManager(p);
+      return null;
+    }
+    const { rerender } = render(<TestComponent p={props} />);
+    return {
+      result: {
+        get current() {
+          return hookResult;
+        },
+      },
+      rerender: (newProps: BackgroundShellManagerProps) =>
+        rerender(<TestComponent p={newProps} />),
+    };
+  };
+
+  it('should initialize with correct default values', () => {
+    const backgroundShells = new Map<number, BackgroundShell>();
+    const { result } = renderHook({
+      backgroundShells,
+      backgroundShellCount: 0,
+      isBackgroundShellVisible: false,
+      activePtyId: null,
+      embeddedShellFocused: false,
+      setEmbeddedShellFocused,
+      terminalHeight,
+    });
+
+    expect(result.current.isBackgroundShellListOpen).toBe(false);
+    expect(result.current.activeBackgroundShellPid).toBe(null);
+    expect(result.current.backgroundShellHeight).toBe(0);
+  });
+
+  it('should auto-select the first background shell when added', () => {
+    const backgroundShells = new Map<number, BackgroundShell>();
+    const { result, rerender } = renderHook({
+      backgroundShells,
+      backgroundShellCount: 0,
+      isBackgroundShellVisible: false,
+      activePtyId: null,
+      embeddedShellFocused: false,
+      setEmbeddedShellFocused,
+      terminalHeight,
+    });
+
+    const newShells = new Map<number, BackgroundShell>([
+      [123, {} as BackgroundShell],
+    ]);
+    rerender({
+      backgroundShells: newShells,
+      backgroundShellCount: 1,
+      isBackgroundShellVisible: false,
+      activePtyId: null,
+      embeddedShellFocused: false,
+      setEmbeddedShellFocused,
+      terminalHeight,
+    });
+
+    expect(result.current.activeBackgroundShellPid).toBe(123);
+  });
+
+  it('should reset state when all shells are removed', () => {
+    const backgroundShells = new Map<number, BackgroundShell>([
+      [123, {} as BackgroundShell],
+    ]);
+    const { result, rerender } = renderHook({
+      backgroundShells,
+      backgroundShellCount: 1,
+      isBackgroundShellVisible: true,
+      activePtyId: null,
+      embeddedShellFocused: true,
+      setEmbeddedShellFocused,
+      terminalHeight,
+    });
+
+    act(() => {
+      result.current.setIsBackgroundShellListOpen(true);
+    });
+    expect(result.current.isBackgroundShellListOpen).toBe(true);
+
+    rerender({
+      backgroundShells: new Map(),
+      backgroundShellCount: 0,
+      isBackgroundShellVisible: true,
+      activePtyId: null,
+      embeddedShellFocused: true,
+      setEmbeddedShellFocused,
+      terminalHeight,
+    });
+
+    expect(result.current.activeBackgroundShellPid).toBe(null);
+    expect(result.current.isBackgroundShellListOpen).toBe(false);
+  });
+
+  it('should unfocus embedded shell when no shells are active', () => {
+    const backgroundShells = new Map<number, BackgroundShell>([
+      [123, {} as BackgroundShell],
+    ]);
+    renderHook({
+      backgroundShells,
+      backgroundShellCount: 1,
+      isBackgroundShellVisible: false, // Background shell not visible
+      activePtyId: null, // No foreground shell
+      embeddedShellFocused: true,
+      setEmbeddedShellFocused,
+      terminalHeight,
+    });
+
+    expect(setEmbeddedShellFocused).toHaveBeenCalledWith(false);
+  });
+
+  it('should calculate backgroundShellHeight correctly when visible', () => {
+    const backgroundShells = new Map<number, BackgroundShell>([
+      [123, {} as BackgroundShell],
+    ]);
+    const { result } = renderHook({
+      backgroundShells,
+      backgroundShellCount: 1,
+      isBackgroundShellVisible: true,
+      activePtyId: null,
+      embeddedShellFocused: true,
+      setEmbeddedShellFocused,
+      terminalHeight: 100,
+    });
+
+    // 100 * 0.3 = 30
+    expect(result.current.backgroundShellHeight).toBe(30);
+  });
+
+  it('should maintain current active shell if it still exists', () => {
+    const backgroundShells = new Map<number, BackgroundShell>([
+      [123, {} as BackgroundShell],
+      [456, {} as BackgroundShell],
+    ]);
+    const { result, rerender } = renderHook({
+      backgroundShells,
+      backgroundShellCount: 2,
+      isBackgroundShellVisible: true,
+      activePtyId: null,
+      embeddedShellFocused: true,
+      setEmbeddedShellFocused,
+      terminalHeight,
+    });
+
+    act(() => {
+      result.current.setActiveBackgroundShellPid(456);
+    });
+    expect(result.current.activeBackgroundShellPid).toBe(456);
+
+    // Remove the OTHER shell
+    const updatedShells = new Map<number, BackgroundShell>([
+      [456, {} as BackgroundShell],
+    ]);
+    rerender({
+      backgroundShells: updatedShells,
+      backgroundShellCount: 1,
+      isBackgroundShellVisible: true,
+      activePtyId: null,
+      embeddedShellFocused: true,
+      setEmbeddedShellFocused,
+      terminalHeight,
+    });
+
+    expect(result.current.activeBackgroundShellPid).toBe(456);
+  });
+});

packages/cli/src/ui/hooks/useBackgroundShellManager.ts

@@ -0,0 +1,91 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { useState, useEffect, useMemo } from 'react';
+import { type BackgroundShell } from './shellCommandProcessor.js';
+
+export interface BackgroundShellManagerProps {
+  backgroundShells: Map<number, BackgroundShell>;
+  backgroundShellCount: number;
+  isBackgroundShellVisible: boolean;
+  activePtyId: number | null | undefined;
+  embeddedShellFocused: boolean;
+  setEmbeddedShellFocused: (focused: boolean) => void;
+  terminalHeight: number;
+}
+
+export function useBackgroundShellManager({
+  backgroundShells,
+  backgroundShellCount,
+  isBackgroundShellVisible,
+  activePtyId,
+  embeddedShellFocused,
+  setEmbeddedShellFocused,
+  terminalHeight,
+}: BackgroundShellManagerProps) {
+  const [isBackgroundShellListOpen, setIsBackgroundShellListOpen] =
+    useState(false);
+  const [activeBackgroundShellPid, setActiveBackgroundShellPid] = useState<
+    number | null
+  >(null);
+
+  useEffect(() => {
+    if (backgroundShells.size === 0) {
+      if (activeBackgroundShellPid !== null) {
+        setActiveBackgroundShellPid(null);
+      }
+      if (isBackgroundShellListOpen) {
+        setIsBackgroundShellListOpen(false);
+      }
+    } else if (
+      activeBackgroundShellPid === null ||
+      !backgroundShells.has(activeBackgroundShellPid)
+    ) {
+      // If active shell is closed or none selected, select the first one (last added usually, or just first in iteration)
+      setActiveBackgroundShellPid(backgroundShells.keys().next().value ?? null);
+    }
+  }, [
+    backgroundShells,
+    activeBackgroundShellPid,
+    backgroundShellCount,
+    isBackgroundShellListOpen,
+  ]);
+
+  useEffect(() => {
+    if (embeddedShellFocused) {
+      const hasActiveForegroundShell = !!activePtyId;
+      const hasVisibleBackgroundShell =
+        isBackgroundShellVisible && backgroundShells.size > 0;
+
+      if (!hasActiveForegroundShell && !hasVisibleBackgroundShell) {
+        setEmbeddedShellFocused(false);
+      }
+    }
+  }, [
+    isBackgroundShellVisible,
+    backgroundShells,
+    embeddedShellFocused,
+    backgroundShellCount,
+    activePtyId,
+    setEmbeddedShellFocused,
+  ]);
+
+  const backgroundShellHeight = useMemo(
+    () =>
+      isBackgroundShellVisible && backgroundShells.size > 0
+        ? Math.max(Math.floor(terminalHeight * 0.3), 5)
+        : 0,
+    [isBackgroundShellVisible, backgroundShells.size, terminalHeight],
+  );
+
+  return {
+    isBackgroundShellListOpen,
+    setIsBackgroundShellListOpen,
+    activeBackgroundShellPid,
+    setActiveBackgroundShellPid,
+    backgroundShellHeight,
+  };
+}

packages/cli/src/ui/hooks/useGeminiStream.test.tsx

@@ -68,6 +68,9 @@ const MockedGeminiClientClass = vi.hoisted(() =>
       recordToolCalls: vi.fn(),
       getConversationFile: vi.fn(),
     });
+    this.getCurrentSequenceModel = vi
+      .fn()
+      .mockReturnValue('gemini-2.0-flash-exp');
   }),
 );
 

packages/cli/src/ui/hooks/useGeminiStream.ts

@@ -43,6 +43,7 @@ import type {
   ServerGeminiStreamEvent as GeminiEvent,
   ThoughtSummary,
   ToolCallRequestInfo,
+  ToolCallResponseInfo,
   GeminiErrorEventValue,
   RetryAttemptPayload,
   ToolCallConfirmationDetails,
@@ -72,6 +73,7 @@ import {
   type TrackedCompletedToolCall,
   type TrackedCancelledToolCall,
   type TrackedWaitingToolCall,
+  type TrackedExecutingToolCall,
 } from './useToolScheduler.js';
 import { promises as fs } from 'node:fs';
 import path from 'node:path';
@@ -79,12 +81,34 @@ import { useSessionStats } from '../contexts/SessionContext.js';
 import { useKeypress } from './useKeypress.js';
 import type { LoadedSettings } from '../../config/settings.js';
 
+type ToolResponseWithParts = ToolCallResponseInfo & {
+  llmContent?: PartListUnion;
+};
+
+interface ShellToolData {
+  pid?: number;
+  command?: string;
+  initialOutput?: string;
+}
+
 enum StreamProcessingStatus {
   Completed,
   UserCancelled,
   Error,
 }
 
+function isShellToolData(data: unknown): data is ShellToolData {
+  if (typeof data !== 'object' || data === null) {
+    return false;
+  }
+  const d = data as Partial<ShellToolData>;
+  return (
+    (d.pid === undefined || typeof d.pid === 'number') &&
+    (d.command === undefined || typeof d.command === 'string') &&
+    (d.initialOutput === undefined || typeof d.initialOutput === 'string')
+  );
+}
+
 function showCitations(settings: LoadedSettings): boolean {
   const enabled = settings.merged.ui.showCitations;
   if (enabled !== undefined) {
@@ -401,14 +425,11 @@ export const useGeminiStream = (
   }, [toolCalls, pushedToolCallIds, config]);
 
   const activeToolPtyId = useMemo(() => {
-    const executingShellTool = toolCalls?.find(
+    const executingShellTool = toolCalls.find(
       (tc) =>
         tc.status === 'executing' && tc.request.name === 'run_shell_command',
     );
-    if (executingShellTool) {
-      return (executingShellTool as { pid?: number }).pid;
-    }
-    return undefined;
+    return (executingShellTool as TrackedExecutingToolCall | undefined)?.pid;
   }, [toolCalls]);
 
   const lastQueryRef = useRef<PartListUnion | null>(null);
@@ -426,18 +447,30 @@ export const useGeminiStream = (
     await done;
     setIsResponding(false);
   }, []);
-  const { handleShellCommand, activeShellPtyId, lastShellOutputTime } =
-    useShellCommandProcessor(
-      addItem,
-      setPendingHistoryItem,
-      onExec,
-      onDebugMessage,
-      config,
-      geminiClient,
-      setShellInputFocused,
-      terminalWidth,
-      terminalHeight,
-    );
+
+  const {
+    handleShellCommand,
+    activeShellPtyId,
+    lastShellOutputTime,
+    backgroundShellCount,
+    isBackgroundShellVisible,
+    toggleBackgroundShell,
+    backgroundCurrentShell,
+    registerBackgroundShell,
+    dismissBackgroundShell,
+    backgroundShells,
+  } = useShellCommandProcessor(
+    addItem,
+    setPendingHistoryItem,
+    onExec,
+    onDebugMessage,
+    config,
+    geminiClient,
+    setShellInputFocused,
+    terminalWidth,
+    terminalHeight,
+    activeToolPtyId,
+  );
 
   const activePtyId = activeShellPtyId || activeToolPtyId;
 
@@ -1404,6 +1437,25 @@ export const useGeminiStream = (
           !processedMemoryToolsRef.current.has(t.request.callId),
       );
 
+      // Handle backgrounded shell tools
+      completedAndReadyToSubmitTools.forEach((t) => {
+        const isShell = t.request.name === 'run_shell_command';
+        // Access result from the tracked tool call response
+        const response = t.response as ToolResponseWithParts;
+        const rawData = response?.data;
+        const data = isShellToolData(rawData) ? rawData : undefined;
+
+        // Use data.pid for shell commands moved to the background.
+        const pid = data?.pid;
+
+        if (isShell && pid) {
+          const command = (data?.['command'] as string) ?? 'shell';
+          const initialOutput = (data?.['initialOutput'] as string) ?? '';
+
+          registerBackgroundShell(pid, command, initialOutput);
+        }
+      });
+
       if (newSuccessfulMemorySaves.length > 0) {
         // Perform the refresh only if there are new ones.
         void performMemoryRefresh();
@@ -1510,6 +1562,7 @@ export const useGeminiStream = (
       performMemoryRefresh,
       modelSwitchedFromQuotaError,
       addItem,
+      registerBackgroundShell,
     ],
   );
 
@@ -1599,6 +1652,12 @@ export const useGeminiStream = (
     activePtyId,
     loopDetectionConfirmationRequest,
     lastOutputTime,
+    backgroundShellCount,
+    isBackgroundShellVisible,
+    toggleBackgroundShell,
+    backgroundCurrentShell,
+    backgroundShells,
+    dismissBackgroundShell,
     retryStatus,
   };
 };

packages/cli/src/ui/hooks/useReactToolScheduler.ts

@@ -40,7 +40,6 @@ export type TrackedWaitingToolCall = WaitingToolCall & {
 };
 export type TrackedExecutingToolCall = ExecutingToolCall & {
   responseSubmittedToGemini?: boolean;
-  pid?: number;
 };
 export type TrackedCompletedToolCall = CompletedToolCall & {
   responseSubmittedToGemini?: boolean;
@@ -134,7 +133,15 @@ export function useReactToolScheduler(
               ...coreTc,
               responseSubmittedToGemini,
               liveOutput,
-              pid: coreTc.pid,
+            };
+          } else if (
+            coreTc.status === 'success' ||
+            coreTc.status === 'error' ||
+            coreTc.status === 'cancelled'
+          ) {
+            return {
+              ...coreTc,
+              responseSubmittedToGemini,
             };
           } else {
             return {