refactor(cli): simplify command completion orchestration and fix shell cache race

- Simplified `useCommandCompletion.tsx` by moving shell-specific tokenization into `useShellCompletion.ts`.
- Reverted most changes to the `useCommandCompletion` `useMemo` block to keep it clean and consistent with other modes.
- Fixed a potential race condition in `useShellCompletion.ts` where `scanPathExecutables` could be called multiple times if it was slow. It now caches the Promise itself.
- Updated tests to match the refined hook interfaces.

package-lock.json

@@ -17419,6 +17419,7 @@
         "shell-quote": "^1.8.3",
         "simple-git": "^3.28.0",
         "strip-ansi": "^7.1.0",
+        "strip-json-comments": "^3.1.1",
         "systeminformation": "^5.25.11",
         "tree-sitter-bash": "^0.25.0",
         "undici": "^7.10.0",

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

@@ -411,6 +411,73 @@ describe('InputPrompt', () => {
     unmount();
   });
 
+  it('should submit command in shell mode when Enter pressed with suggestions visible but no arrow navigation', async () => {
+    props.shellModeActive = true;
+    props.buffer.setText('ls ');
+
+    mockedUseCommandCompletion.mockReturnValue({
+      ...mockCommandCompletion,
+      showSuggestions: true,
+      suggestions: [
+        { label: 'dir1', value: 'dir1' },
+        { label: 'dir2', value: 'dir2' },
+      ],
+      activeSuggestionIndex: 0,
+    });
+
+    const { stdin, unmount } = renderWithProviders(<InputPrompt {...props} />, {
+      uiActions,
+    });
+
+    // Press Enter without navigating — should dismiss suggestions and fall
+    // through to the main submit handler.
+    await act(async () => {
+      stdin.write('\r');
+    });
+    await waitFor(() => {
+      expect(mockCommandCompletion.resetCompletionState).toHaveBeenCalled();
+      expect(props.onSubmit).toHaveBeenCalledWith('ls'); // Assert fall-through (text is trimmed)
+    });
+    expect(mockCommandCompletion.handleAutocomplete).not.toHaveBeenCalled();
+    unmount();
+  });
+
+  it('should accept suggestion in shell mode when Enter pressed after arrow navigation', async () => {
+    props.shellModeActive = true;
+    props.buffer.setText('ls ');
+
+    mockedUseCommandCompletion.mockReturnValue({
+      ...mockCommandCompletion,
+      showSuggestions: true,
+      suggestions: [
+        { label: 'dir1', value: 'dir1' },
+        { label: 'dir2', value: 'dir2' },
+      ],
+      activeSuggestionIndex: 1,
+    });
+
+    const { stdin, unmount } = renderWithProviders(<InputPrompt {...props} />, {
+      uiActions,
+    });
+
+    // Press ArrowDown to navigate, then Enter to accept
+    await act(async () => {
+      stdin.write('\u001B[B'); // ArrowDown — sets hasUserNavigatedSuggestions
+    });
+    await waitFor(() =>
+      expect(mockCommandCompletion.navigateDown).toHaveBeenCalled(),
+    );
+
+    await act(async () => {
+      stdin.write('\r'); // Enter — should accept navigated suggestion
+    });
+    await waitFor(() => {
+      expect(mockCommandCompletion.handleAutocomplete).toHaveBeenCalledWith(1);
+    });
+    expect(props.onSubmit).not.toHaveBeenCalled();
+    unmount();
+  });
+
   it('should NOT call shell history methods when not in shell mode', async () => {
     props.buffer.setText('some text');
     const { stdin, unmount } = renderWithProviders(<InputPrompt {...props} />, {

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

@@ -259,6 +259,7 @@ export const InputPrompt: React.FC<InputPromptProps> = ({
   >(null);
   const pasteTimeoutRef = useRef<NodeJS.Timeout | null>(null);
   const innerBoxRef = useRef<DOMElement>(null);
+  const hasUserNavigatedSuggestions = useRef(false);
 
   const [reverseSearchActive, setReverseSearchActive] = useState(false);
   const [commandSearchActive, setCommandSearchActive] = useState(false);
@@ -615,6 +616,7 @@ export const InputPrompt: React.FC<InputPromptProps> = ({
         setSuppressCompletion(
           isHistoryNav || isCursorMovement || keyMatchers[Command.ESCAPE](key),
         );
+        hasUserNavigatedSuggestions.current = false;
       }
 
       // TODO(jacobr): this special case is likely not needed anymore.
@@ -648,7 +650,13 @@ export const InputPrompt: React.FC<InputPromptProps> = ({
         Boolean(completion.promptCompletion.text) ||
         reverseSearchActive ||
         commandSearchActive;
-      if (isPlainTab) {
+
+      if (isPlainTab && shellModeActive) {
+        resetPlainTabPress();
+        if (!completion.showSuggestions) {
+          setSuppressCompletion(false);
+        }
+      } else if (isPlainTab) {
         if (!hasTabCompletionInteraction) {
           if (registerPlainTabPress() === 2) {
             toggleCleanUiDetailsVisible();
@@ -892,7 +900,9 @@ export const InputPrompt: React.FC<InputPromptProps> = ({
         completion.isPerfectMatch &&
         keyMatchers[Command.SUBMIT](key) &&
         recentUnsafePasteTime === null &&
-        (!completion.showSuggestions || completion.activeSuggestionIndex <= 0)
+        (!completion.showSuggestions ||
+          (completion.activeSuggestionIndex <= 0 &&
+            !hasUserNavigatedSuggestions.current))
       ) {
         handleSubmit(buffer.text);
         return true;
@@ -908,11 +918,13 @@ export const InputPrompt: React.FC<InputPromptProps> = ({
         if (completion.suggestions.length > 1) {
           if (keyMatchers[Command.COMPLETION_UP](key)) {
             completion.navigateUp();
+            hasUserNavigatedSuggestions.current = true;
             setExpandedSuggestionIndex(-1); // Reset expansion when navigating
             return true;
           }
           if (keyMatchers[Command.COMPLETION_DOWN](key)) {
             completion.navigateDown();
+            hasUserNavigatedSuggestions.current = true;
             setExpandedSuggestionIndex(-1); // Reset expansion when navigating
             return true;
           }
@@ -930,6 +942,24 @@ export const InputPrompt: React.FC<InputPromptProps> = ({
 
               const isEnterKey = key.name === 'return' && !key.ctrl;
 
+              if (isEnterKey && shellModeActive) {
+                if (hasUserNavigatedSuggestions.current) {
+                  completion.handleAutocomplete(
+                    completion.activeSuggestionIndex,
+                  );
+                  setExpandedSuggestionIndex(-1);
+                  hasUserNavigatedSuggestions.current = false;
+                  return true;
+                }
+                completion.resetCompletionState();
+                setExpandedSuggestionIndex(-1);
+                hasUserNavigatedSuggestions.current = false;
+                if (buffer.text.trim()) {
+                  handleSubmit(buffer.text);
+                }
+                return true;
+              }
+
               if (isEnterKey && buffer.text.startsWith('/')) {
                 const { isArgumentCompletion, leafCommand } =
                   completion.slashCompletionRange;
@@ -1386,7 +1416,8 @@ export const InputPrompt: React.FC<InputPromptProps> = ({
         scrollOffset={activeCompletion.visibleStartIndex}
         userInput={buffer.text}
         mode={
-          completion.completionMode === CompletionMode.AT
+          completion.completionMode === CompletionMode.AT ||
+          completion.completionMode === CompletionMode.SHELL
             ? 'reverse'
             : buffer.text.startsWith('/') &&
                 !reverseSearchActive &&

packages/cli/src/ui/hooks/shell-completions/gitProvider.test.ts

@@ -0,0 +1,131 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { describe, it, expect, vi, beforeEach } from 'vitest';
+import { gitProvider } from './gitProvider.js';
+import * as childProcess from 'node:child_process';
+
+vi.mock('node:child_process', async (importOriginal) => {
+  const actual = await importOriginal<typeof import('node:child_process')>();
+  return {
+    ...actual,
+    execFile: vi.fn(),
+  };
+});
+
+describe('gitProvider', () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+  });
+
+  it('suggests git subcommands for cursorIndex 1', async () => {
+    const result = await gitProvider.getCompletions(['git', 'ch'], 1, '/tmp');
+
+    expect(result.exclusive).toBe(true);
+    expect(result.suggestions).toEqual(
+      expect.arrayContaining([expect.objectContaining({ value: 'checkout' })]),
+    );
+    expect(
+      result.suggestions.find((s) => s.value === 'commit'),
+    ).toBeUndefined();
+  });
+
+  it('suggests branch names for checkout at cursorIndex 2', async () => {
+    vi.mocked(childProcess.execFile).mockImplementation(
+      (_cmd, _args, _opts, cb: unknown) => {
+        const callback = (typeof _opts === 'function' ? _opts : cb) as (
+          error: Error | null,
+          result: { stdout: string },
+        ) => void;
+        callback(null, {
+          stdout: 'main\nfeature-branch\nfix/bug\nbranch(with)special\n',
+        });
+        return {} as ReturnType<typeof childProcess.execFile>;
+      },
+    );
+
+    const result = await gitProvider.getCompletions(
+      ['git', 'checkout', 'feat'],
+      2,
+      '/tmp',
+    );
+
+    expect(result.exclusive).toBe(true);
+    expect(result.suggestions).toHaveLength(1);
+    expect(result.suggestions[0].label).toBe('feature-branch');
+    expect(result.suggestions[0].value).toBe('feature-branch');
+    expect(childProcess.execFile).toHaveBeenCalledWith(
+      'git',
+      ['branch', '--format=%(refname:short)'],
+      expect.any(Object),
+      expect.any(Function),
+    );
+  });
+
+  it('escapes branch names with shell metacharacters', async () => {
+    vi.mocked(childProcess.execFile).mockImplementation(
+      (_cmd, _args, _opts, cb: unknown) => {
+        const callback = (typeof _opts === 'function' ? _opts : cb) as (
+          error: Error | null,
+          result: { stdout: string },
+        ) => void;
+        callback(null, { stdout: 'main\nbranch(with)special\n' });
+        return {} as ReturnType<typeof childProcess.execFile>;
+      },
+    );
+
+    const result = await gitProvider.getCompletions(
+      ['git', 'checkout', 'branch('],
+      2,
+      '/tmp',
+    );
+
+    expect(result.exclusive).toBe(true);
+    expect(result.suggestions).toHaveLength(1);
+    expect(result.suggestions[0].label).toBe('branch(with)special');
+
+    // On Windows, space escape is not done. But since UNIX_SHELL_SPECIAL_CHARS is mostly tested,
+    // we can use a matcher that checks if escaping was applied (it differs per platform but that's handled by escapeShellPath).
+    // Let's match the value against either unescaped (win) or escaped (unix).
+    const isWin = process.platform === 'win32';
+    expect(result.suggestions[0].value).toBe(
+      isWin ? 'branch(with)special' : 'branch\\(with\\)special',
+    );
+  });
+
+  it('returns empty results if git branch fails', async () => {
+    vi.mocked(childProcess.execFile).mockImplementation(
+      (_cmd, _args, _opts, cb: unknown) => {
+        const callback = (typeof _opts === 'function' ? _opts : cb) as (
+          error: Error,
+          stdout?: string,
+        ) => void;
+        callback(new Error('Not a git repository'));
+        return {} as ReturnType<typeof childProcess.execFile>;
+      },
+    );
+
+    const result = await gitProvider.getCompletions(
+      ['git', 'checkout', ''],
+      2,
+      '/tmp',
+    );
+
+    expect(result.exclusive).toBe(true);
+    expect(result.suggestions).toHaveLength(0);
+  });
+
+  it('returns non-exclusive for unrecognized position', async () => {
+    const result = await gitProvider.getCompletions(
+      ['git', 'commit', '-m', 'some message'],
+      3,
+      '/tmp',
+    );
+
+    expect(result.exclusive).toBe(false);
+    expect(result.suggestions).toHaveLength(0);
+  });
+});

packages/cli/src/ui/hooks/shell-completions/gitProvider.ts

@@ -0,0 +1,93 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { execFile } from 'node:child_process';
+import { promisify } from 'node:util';
+import type { ShellCompletionProvider, CompletionResult } from './types.js';
+import { escapeShellPath } from '../useShellCompletion.js';
+
+const execFileAsync = promisify(execFile);
+
+const GIT_SUBCOMMANDS = [
+  'add',
+  'branch',
+  'checkout',
+  'commit',
+  'diff',
+  'merge',
+  'pull',
+  'push',
+  'rebase',
+  'status',
+  'switch',
+];
+
+export const gitProvider: ShellCompletionProvider = {
+  command: 'git',
+  async getCompletions(
+    tokens: string[],
+    cursorIndex: number,
+    cwd: string,
+    signal?: AbortSignal,
+  ): Promise<CompletionResult> {
+    // We are completing the first argument (subcommand)
+    if (cursorIndex === 1) {
+      const partial = tokens[1] || '';
+      return {
+        suggestions: GIT_SUBCOMMANDS.filter((cmd) =>
+          cmd.startsWith(partial),
+        ).map((cmd) => ({
+          label: cmd,
+          value: cmd,
+          description: 'git command',
+        })),
+        exclusive: true,
+      };
+    }
+
+    // We are completing the second argument (e.g. branch name)
+    if (cursorIndex === 2) {
+      const subcommand = tokens[1];
+      if (
+        subcommand === 'checkout' ||
+        subcommand === 'switch' ||
+        subcommand === 'merge' ||
+        subcommand === 'branch'
+      ) {
+        const partial = tokens[2] || '';
+        try {
+          const { stdout } = await execFileAsync(
+            'git',
+            ['branch', '--format=%(refname:short)'],
+            { cwd, signal },
+          );
+
+          const branches = stdout
+            .split('\n')
+            .map((b) => b.trim())
+            .filter(Boolean);
+
+          return {
+            suggestions: branches
+              .filter((b) => b.startsWith(partial))
+              .map((b) => ({
+                label: b,
+                value: escapeShellPath(b),
+                description: 'branch',
+              })),
+            exclusive: true,
+          };
+        } catch {
+          // If git fails (e.g. not a git repo), return nothing
+          return { suggestions: [], exclusive: true };
+        }
+      }
+    }
+
+    // Unhandled git argument, fallback to default file completions
+    return { suggestions: [], exclusive: false };
+  },
+};

packages/cli/src/ui/hooks/shell-completions/index.ts

@@ -0,0 +1,25 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import type { ShellCompletionProvider, CompletionResult } from './types.js';
+import { gitProvider } from './gitProvider.js';
+import { npmProvider } from './npmProvider.js';
+
+const providers: ShellCompletionProvider[] = [gitProvider, npmProvider];
+
+export async function getArgumentCompletions(
+  commandToken: string,
+  tokens: string[],
+  cursorIndex: number,
+  cwd: string,
+  signal?: AbortSignal,
+): Promise<CompletionResult | null> {
+  const provider = providers.find((p) => p.command === commandToken);
+  if (!provider) {
+    return null;
+  }
+  return provider.getCompletions(tokens, cursorIndex, cwd, signal);
+}

packages/cli/src/ui/hooks/shell-completions/npmProvider.test.ts

@@ -0,0 +1,106 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { describe, it, expect, vi, beforeEach } from 'vitest';
+import { npmProvider } from './npmProvider.js';
+import * as fs from 'node:fs/promises';
+
+vi.mock('node:fs/promises', () => ({
+  readFile: vi.fn(),
+}));
+
+describe('npmProvider', () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+  });
+
+  it('suggests npm subcommands for cursorIndex 1', async () => {
+    const result = await npmProvider.getCompletions(['npm', 'ru'], 1, '/tmp');
+
+    expect(result.exclusive).toBe(true);
+    expect(result.suggestions).toEqual([
+      expect.objectContaining({ value: 'run' }),
+    ]);
+  });
+
+  it('suggests package.json scripts for npm run at cursorIndex 2', async () => {
+    const mockPackageJson = {
+      scripts: {
+        start: 'node index.js',
+        build: 'tsc',
+        'build:dev': 'tsc --watch',
+      },
+    };
+    vi.mocked(fs.readFile).mockResolvedValue(JSON.stringify(mockPackageJson));
+
+    const result = await npmProvider.getCompletions(
+      ['npm', 'run', 'bu'],
+      2,
+      '/tmp',
+    );
+
+    expect(result.exclusive).toBe(true);
+    expect(result.suggestions).toHaveLength(2);
+    expect(result.suggestions[0].label).toBe('build');
+    expect(result.suggestions[0].value).toBe('build');
+    expect(result.suggestions[1].label).toBe('build:dev');
+    expect(result.suggestions[1].value).toBe('build:dev');
+    expect(fs.readFile).toHaveBeenCalledWith(
+      expect.stringContaining('package.json'),
+      'utf8',
+    );
+  });
+
+  it('escapes script names with shell metacharacters', async () => {
+    const mockPackageJson = {
+      scripts: {
+        'build(prod)': 'tsc',
+        'test:watch': 'vitest',
+      },
+    };
+    vi.mocked(fs.readFile).mockResolvedValue(JSON.stringify(mockPackageJson));
+
+    const result = await npmProvider.getCompletions(
+      ['npm', 'run', 'bu'],
+      2,
+      '/tmp',
+    );
+
+    expect(result.exclusive).toBe(true);
+    expect(result.suggestions).toHaveLength(1);
+    expect(result.suggestions[0].label).toBe('build(prod)');
+
+    // Windows does not escape spaces/parens in cmds by default in our function, but Unix does.
+    const isWin = process.platform === 'win32';
+    expect(result.suggestions[0].value).toBe(
+      isWin ? 'build(prod)' : 'build\\(prod\\)',
+    );
+  });
+
+  it('handles missing package.json gracefully', async () => {
+    vi.mocked(fs.readFile).mockRejectedValue(new Error('ENOENT'));
+
+    const result = await npmProvider.getCompletions(
+      ['npm', 'run', ''],
+      2,
+      '/tmp',
+    );
+
+    expect(result.exclusive).toBe(true);
+    expect(result.suggestions).toHaveLength(0);
+  });
+
+  it('returns non-exclusive for unrecognized position', async () => {
+    const result = await npmProvider.getCompletions(
+      ['npm', 'install', 'react'],
+      2,
+      '/tmp',
+    );
+
+    expect(result.exclusive).toBe(false);
+    expect(result.suggestions).toHaveLength(0);
+  });
+});

packages/cli/src/ui/hooks/shell-completions/npmProvider.ts

@@ -0,0 +1,81 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import * as fs from 'node:fs/promises';
+import * as path from 'node:path';
+import type { ShellCompletionProvider, CompletionResult } from './types.js';
+import { escapeShellPath } from '../useShellCompletion.js';
+
+const NPM_SUBCOMMANDS = [
+  'build',
+  'ci',
+  'dev',
+  'install',
+  'publish',
+  'run',
+  'start',
+  'test',
+];
+
+export const npmProvider: ShellCompletionProvider = {
+  command: 'npm',
+  async getCompletions(
+    tokens: string[],
+    cursorIndex: number,
+    cwd: string,
+    signal?: AbortSignal,
+  ): Promise<CompletionResult> {
+    if (cursorIndex === 1) {
+      const partial = tokens[1] || '';
+      return {
+        suggestions: NPM_SUBCOMMANDS.filter((cmd) =>
+          cmd.startsWith(partial),
+        ).map((cmd) => ({
+          label: cmd,
+          value: cmd,
+          description: 'npm command',
+        })),
+        exclusive: true,
+      };
+    }
+
+    if (cursorIndex === 2 && tokens[1] === 'run') {
+      const partial = tokens[2] || '';
+      try {
+        if (signal?.aborted) return { suggestions: [], exclusive: true };
+
+        const pkgJsonPath = path.join(cwd, 'package.json');
+        const content = await fs.readFile(pkgJsonPath, 'utf8');
+        const pkg = JSON.parse(content) as unknown;
+
+        const scripts =
+          pkg &&
+          typeof pkg === 'object' &&
+          'scripts' in pkg &&
+          pkg.scripts &&
+          typeof pkg.scripts === 'object'
+            ? Object.keys(pkg.scripts)
+            : [];
+
+        return {
+          suggestions: scripts
+            .filter((s) => s.startsWith(partial))
+            .map((s) => ({
+              label: s,
+              value: escapeShellPath(s),
+              description: 'npm script',
+            })),
+          exclusive: true,
+        };
+      } catch {
+        // No package.json or invalid JSON
+        return { suggestions: [], exclusive: true };
+      }
+    }
+
+    return { suggestions: [], exclusive: false };
+  },
+};

packages/cli/src/ui/hooks/shell-completions/types.ts

@@ -0,0 +1,24 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import type { Suggestion } from '../../components/SuggestionsDisplay.js';
+
+export interface CompletionResult {
+  suggestions: Suggestion[];
+  // If true, this prevents the shell from appending generic file/path completions
+  // to this list. Use this when the tool expects ONLY specific values (e.g. branches).
+  exclusive?: boolean;
+}
+
+export interface ShellCompletionProvider {
+  command: string; // The command trigger, e.g., 'git' or 'npm'
+  getCompletions(
+    tokens: string[], // List of arguments parsed from the input
+    cursorIndex: number, // Which token index the cursor is currently on
+    cwd: string,
+    signal?: AbortSignal,
+  ): Promise<CompletionResult>;
+}

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

@@ -28,6 +28,7 @@ import type { UseAtCompletionProps } from './useAtCompletion.js';
 import { useAtCompletion } from './useAtCompletion.js';
 import type { UseSlashCompletionProps } from './useSlashCompletion.js';
 import { useSlashCompletion } from './useSlashCompletion.js';
+import { useShellCompletion } from './useShellCompletion.js';
 
 vi.mock('./useAtCompletion', () => ({
   useAtCompletion: vi.fn(),
@@ -40,19 +41,35 @@ vi.mock('./useSlashCompletion', () => ({
   })),
 }));
 
+vi.mock('./useShellCompletion', () => ({
+  useShellCompletion: vi.fn(() => ({
+    completionStart: 0,
+    completionEnd: 0,
+    query: '',
+  })),
+}));
+
 // Helper to set up mocks in a consistent way for both child hooks
 const setupMocks = ({
   atSuggestions = [],
   slashSuggestions = [],
+  shellSuggestions = [],
   isLoading = false,
   isPerfectMatch = false,
   slashCompletionRange = { completionStart: 0, completionEnd: 0 },
+  shellCompletionRange = { completionStart: 0, completionEnd: 0, query: '' },
 }: {
   atSuggestions?: Suggestion[];
   slashSuggestions?: Suggestion[];
+  shellSuggestions?: Suggestion[];
   isLoading?: boolean;
   isPerfectMatch?: boolean;
   slashCompletionRange?: { completionStart: number; completionEnd: number };
+  shellCompletionRange?: {
+    completionStart: number;
+    completionEnd: number;
+    query: string;
+  };
 }) => {
   // Mock for @-completions
   (useAtCompletion as Mock).mockImplementation(
@@ -89,11 +106,25 @@ const setupMocks = ({
       return slashCompletionRange;
     },
   );
+
+  // Mock for shell completions
+  (useShellCompletion as Mock).mockImplementation(
+    ({ enabled, setSuggestions, setIsLoadingSuggestions }) => {
+      useEffect(() => {
+        if (enabled) {
+          setIsLoadingSuggestions(isLoading);
+          setSuggestions(shellSuggestions);
+        }
+      }, [enabled, setSuggestions, setIsLoadingSuggestions]);
+      return shellCompletionRange;
+    },
+  );
 };
 
 describe('useCommandCompletion', () => {
   const mockCommandContext = {} as CommandContext;
   const mockConfig = {
+    getEnablePromptCompletion: () => false,
     getGeminiClient: vi.fn(),
   } as unknown as Config;
   const testRootDir = '/';
@@ -498,6 +529,7 @@ describe('useCommandCompletion', () => {
   describe('prompt completion filtering', () => {
     it('should not trigger prompt completion for line comments', async () => {
       const mockConfig = {
+        getEnablePromptCompletion: () => true,
         getGeminiClient: vi.fn(),
       } as unknown as Config;
 
@@ -530,6 +562,7 @@ describe('useCommandCompletion', () => {
 
     it('should not trigger prompt completion for block comments', async () => {
       const mockConfig = {
+        getEnablePromptCompletion: () => true,
         getGeminiClient: vi.fn(),
       } as unknown as Config;
 
@@ -564,6 +597,7 @@ describe('useCommandCompletion', () => {
 
     it('should trigger prompt completion for regular text when enabled', async () => {
       const mockConfig = {
+        getEnablePromptCompletion: () => true,
         getGeminiClient: vi.fn(),
       } as unknown as Config;
 

packages/cli/src/ui/hooks/useCommandCompletion.tsx

@@ -13,6 +13,7 @@ import { isSlashCommand } from '../utils/commandUtils.js';
 import { toCodePoints } from '../utils/textUtils.js';
 import { useAtCompletion } from './useAtCompletion.js';
 import { useSlashCompletion } from './useSlashCompletion.js';
+import { useShellCompletion } from './useShellCompletion.js';
 import type { PromptCompletion } from './usePromptCompletion.js';
 import {
   usePromptCompletion,
@@ -26,6 +27,7 @@ export enum CompletionMode {
   AT = 'AT',
   SLASH = 'SLASH',
   PROMPT = 'PROMPT',
+  SHELL = 'SHELL',
 }
 
 export interface UseCommandCompletionReturn {
@@ -99,89 +101,105 @@ export function useCommandCompletion({
   const cursorRow = buffer.cursor[0];
   const cursorCol = buffer.cursor[1];
 
-  const { completionMode, query, completionStart, completionEnd } =
-    useMemo(() => {
-      const currentLine = buffer.lines[cursorRow] || '';
-      const codePoints = toCodePoints(currentLine);
-
-      // FIRST: Check for @ completion (scan backwards from cursor)
-      // This must happen before slash command check so that `/cmd @file`
-      // triggers file completion, not just slash command completion.
-      for (let i = cursorCol - 1; i >= 0; i--) {
-        const char = codePoints[i];
-
-        if (char === ' ') {
-          let backslashCount = 0;
-          for (let j = i - 1; j >= 0 && codePoints[j] === '\\'; j--) {
-            backslashCount++;
-          }
-          if (backslashCount % 2 === 0) {
-            break;
-          }
-        } else if (char === '@') {
-          let end = codePoints.length;
-          for (let i = cursorCol; i < codePoints.length; i++) {
-            if (codePoints[i] === ' ') {
-              let backslashCount = 0;
-              for (let j = i - 1; j >= 0 && codePoints[j] === '\\'; j--) {
-                backslashCount++;
-              }
-
-              if (backslashCount % 2 === 0) {
-                end = i;
-                break;
-              }
-            }
-          }
-          const pathStart = i + 1;
-          const partialPath = currentLine.substring(pathStart, end);
-          return {
-            completionMode: CompletionMode.AT,
-            query: partialPath,
-            completionStart: pathStart,
-            completionEnd: end,
-          };
-        }
-      }
-
-      // THEN: Check for slash command (only if no @ completion is active)
-      if (cursorRow === 0 && isSlashCommand(currentLine.trim())) {
-        return {
-          completionMode: CompletionMode.SLASH,
-          query: currentLine,
-          completionStart: 0,
-          completionEnd: currentLine.length,
-        };
-      }
-
-      // Check for prompt completion - only if enabled
-      const trimmedText = buffer.text.trim();
-      const isPromptCompletionEnabled = false;
-      if (
-        isPromptCompletionEnabled &&
-        trimmedText.length >= PROMPT_COMPLETION_MIN_LENGTH &&
-        !isSlashCommand(trimmedText) &&
-        !trimmedText.includes('@')
-      ) {
-        return {
-          completionMode: CompletionMode.PROMPT,
-          query: trimmedText,
-          completionStart: 0,
-          completionEnd: trimmedText.length,
-        };
-      }
+  const {
+    completionMode,
+    query: memoQuery,
+    completionStart,
+    completionEnd,
+  } = useMemo(() => {
+    const currentLine = buffer.lines[cursorRow] || '';
+    const codePoints = toCodePoints(currentLine);
 
+    if (shellModeActive) {
       return {
-        completionMode: CompletionMode.IDLE,
-        query: null,
+        completionMode:
+          currentLine.trim().length === 0
+            ? CompletionMode.IDLE
+            : CompletionMode.SHELL,
+        query: '',
         completionStart: -1,
         completionEnd: -1,
       };
-    }, [cursorRow, cursorCol, buffer.lines, buffer.text]);
+    }
+
+    // FIRST: Check for @ completion (scan backwards from cursor)
+    // This must happen before slash command check so that `/cmd @file`
+    // triggers file completion, not just slash command completion.
+    for (let i = cursorCol - 1; i >= 0; i--) {
+      const char = codePoints[i];
+
+      if (char === ' ') {
+        let backslashCount = 0;
+        for (let j = i - 1; j >= 0 && codePoints[j] === '\\'; j--) {
+          backslashCount++;
+        }
+        if (backslashCount % 2 === 0) {
+          break;
+        }
+      } else if (char === '@') {
+        let end = codePoints.length;
+        for (let i = cursorCol; i < codePoints.length; i++) {
+          if (codePoints[i] === ' ') {
+            let backslashCount = 0;
+            for (let j = i - 1; j >= 0 && codePoints[j] === '\\'; j--) {
+              backslashCount++;
+            }
+
+            if (backslashCount % 2 === 0) {
+              end = i;
+              break;
+            }
+          }
+        }
+        const pathStart = i + 1;
+        const partialPath = currentLine.substring(pathStart, end);
+        return {
+          completionMode: CompletionMode.AT,
+          query: partialPath,
+          completionStart: pathStart,
+          completionEnd: end,
+        };
+      }
+    }
+
+    // THEN: Check for slash command (only if no @ completion is active)
+    if (cursorRow === 0 && isSlashCommand(currentLine.trim())) {
+      return {
+        completionMode: CompletionMode.SLASH,
+        query: currentLine,
+        completionStart: 0,
+        completionEnd: currentLine.length,
+      };
+    }
+
+    // Check for prompt completion - only if enabled
+    const trimmedText = buffer.text.trim();
+    const isPromptCompletionEnabled = false;
+    if (
+      isPromptCompletionEnabled &&
+      trimmedText.length >= PROMPT_COMPLETION_MIN_LENGTH &&
+      !isSlashCommand(trimmedText) &&
+      !trimmedText.includes('@')
+    ) {
+      return {
+        completionMode: CompletionMode.PROMPT,
+        query: trimmedText,
+        completionStart: 0,
+        completionEnd: trimmedText.length,
+      };
+    }
+
+    return {
+      completionMode: CompletionMode.IDLE,
+      query: null,
+      completionStart: -1,
+      completionEnd: -1,
+    };
+  }, [cursorRow, cursorCol, buffer.lines, buffer.text, shellModeActive]);
 
   useAtCompletion({
     enabled: active && completionMode === CompletionMode.AT,
-    pattern: query || '',
+    pattern: memoQuery || '',
     config,
     cwd,
     setSuggestions,
@@ -191,7 +209,7 @@ export function useCommandCompletion({
   const slashCompletionRange = useSlashCompletion({
     enabled:
       active && completionMode === CompletionMode.SLASH && !shellModeActive,
-    query,
+    query: memoQuery,
     slashCommands,
     commandContext,
     setSuggestions,
@@ -199,9 +217,22 @@ export function useCommandCompletion({
     setIsPerfectMatch,
   });
 
+  const shellCompletionRange = useShellCompletion({
+    enabled: active && completionMode === CompletionMode.SHELL,
+    line: buffer.lines[cursorRow] || '',
+    cursorCol,
+    cwd,
+    setSuggestions,
+    setIsLoadingSuggestions,
+  });
+
+  const query =
+    completionMode === CompletionMode.SHELL
+      ? shellCompletionRange.query
+      : memoQuery;
+
   const promptCompletion = usePromptCompletion({
     buffer,
-    config,
   });
 
   useEffect(() => {
@@ -258,6 +289,9 @@ export function useCommandCompletion({
       if (completionMode === CompletionMode.SLASH) {
         start = slashCompletionRange.completionStart;
         end = slashCompletionRange.completionEnd;
+      } else if (completionMode === CompletionMode.SHELL) {
+        start = shellCompletionRange.completionStart;
+        end = shellCompletionRange.completionEnd;
       }
 
       if (start === -1 || end === -1) {
@@ -287,6 +321,7 @@ export function useCommandCompletion({
       completionStart,
       completionEnd,
       slashCompletionRange,
+      shellCompletionRange,
     ],
   );
 
@@ -307,6 +342,9 @@ export function useCommandCompletion({
       if (completionMode === CompletionMode.SLASH) {
         start = slashCompletionRange.completionStart;
         end = slashCompletionRange.completionEnd;
+      } else if (completionMode === CompletionMode.SHELL) {
+        start = shellCompletionRange.completionStart;
+        end = shellCompletionRange.completionEnd;
       }
 
       // Add space padding for Tab completion (auto-execute gets padding from getCompletedText)
@@ -345,6 +383,7 @@ export function useCommandCompletion({
       completionStart,
       completionEnd,
       slashCompletionRange,
+      shellCompletionRange,
       getCompletedText,
     ],
   );

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

@@ -0,0 +1,382 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { describe, it, expect, afterEach, vi } from 'vitest';
+import {
+  getTokenAtCursor,
+  escapeShellPath,
+  resolvePathCompletions,
+  scanPathExecutables,
+} from './useShellCompletion.js';
+import type { FileSystemStructure } from '@google/gemini-cli-test-utils';
+import { createTmpDir, cleanupTmpDir } from '@google/gemini-cli-test-utils';
+
+describe('useShellCompletion utilities', () => {
+  describe('getTokenAtCursor', () => {
+    it('should return empty token struct for empty line', () => {
+      expect(getTokenAtCursor('', 0)).toEqual({
+        token: '',
+        start: 0,
+        end: 0,
+        isFirstToken: true,
+        tokens: [''],
+        cursorIndex: 0,
+        commandToken: '',
+      });
+    });
+
+    it('should extract the first token at cursor position 0', () => {
+      const result = getTokenAtCursor('git status', 3);
+      expect(result).toEqual({
+        token: 'git',
+        start: 0,
+        end: 3,
+        isFirstToken: true,
+        tokens: ['git', 'status'],
+        cursorIndex: 0,
+        commandToken: 'git',
+      });
+    });
+
+    it('should extract the second token when cursor is on it', () => {
+      const result = getTokenAtCursor('git status', 7);
+      expect(result).toEqual({
+        token: 'status',
+        start: 4,
+        end: 10,
+        isFirstToken: false,
+        tokens: ['git', 'status'],
+        cursorIndex: 1,
+        commandToken: 'git',
+      });
+    });
+
+    it('should handle cursor at start of second token', () => {
+      const result = getTokenAtCursor('git status', 4);
+      expect(result).toEqual({
+        token: 'status',
+        start: 4,
+        end: 10,
+        isFirstToken: false,
+        tokens: ['git', 'status'],
+        cursorIndex: 1,
+        commandToken: 'git',
+      });
+    });
+
+    it('should handle escaped spaces', () => {
+      const result = getTokenAtCursor('cat my\\ file.txt', 16);
+      expect(result).toEqual({
+        token: 'my file.txt',
+        start: 4,
+        end: 16,
+        isFirstToken: false,
+        tokens: ['cat', 'my file.txt'],
+        cursorIndex: 1,
+        commandToken: 'cat',
+      });
+    });
+
+    it('should handle single-quoted strings', () => {
+      const result = getTokenAtCursor("cat 'my file.txt'", 17);
+      expect(result).toEqual({
+        token: 'my file.txt',
+        start: 4,
+        end: 17,
+        isFirstToken: false,
+        tokens: ['cat', 'my file.txt'],
+        cursorIndex: 1,
+        commandToken: 'cat',
+      });
+    });
+
+    it('should handle double-quoted strings', () => {
+      const result = getTokenAtCursor('cat "my file.txt"', 17);
+      expect(result).toEqual({
+        token: 'my file.txt',
+        start: 4,
+        end: 17,
+        isFirstToken: false,
+        tokens: ['cat', 'my file.txt'],
+        cursorIndex: 1,
+        commandToken: 'cat',
+      });
+    });
+
+    it('should handle cursor past all tokens (trailing space)', () => {
+      const result = getTokenAtCursor('git ', 4);
+      expect(result).toEqual({
+        token: '',
+        start: 4,
+        end: 4,
+        isFirstToken: false,
+        tokens: ['git', ''],
+        cursorIndex: 1,
+        commandToken: 'git',
+      });
+    });
+
+    it('should handle cursor in the middle of a word', () => {
+      const result = getTokenAtCursor('git checkout main', 7);
+      expect(result).toEqual({
+        token: 'checkout',
+        start: 4,
+        end: 12,
+        isFirstToken: false,
+        tokens: ['git', 'checkout', 'main'],
+        cursorIndex: 1,
+        commandToken: 'git',
+      });
+    });
+
+    it('should mark isFirstToken correctly for first word', () => {
+      const result = getTokenAtCursor('gi', 2);
+      expect(result?.isFirstToken).toBe(true);
+    });
+
+    it('should mark isFirstToken correctly for second word', () => {
+      const result = getTokenAtCursor('git sta', 7);
+      expect(result?.isFirstToken).toBe(false);
+    });
+  });
+
+  describe('escapeShellPath', () => {
+    it('should escape spaces', () => {
+      expect(escapeShellPath('my file.txt')).toBe('my\\ file.txt');
+    });
+
+    it('should escape parentheses', () => {
+      expect(escapeShellPath('file (copy).txt')).toBe('file\\ \\(copy\\).txt');
+    });
+
+    it('should not escape normal characters', () => {
+      expect(escapeShellPath('normal-file.txt')).toBe('normal-file.txt');
+    });
+
+    it('should escape tabs, newlines, carriage returns, and backslashes', () => {
+      expect(escapeShellPath('a\tb')).toBe('a\\\tb');
+      expect(escapeShellPath('a\nb')).toBe('a\\\nb');
+      expect(escapeShellPath('a\rb')).toBe('a\\\rb');
+      expect(escapeShellPath('a\\b')).toBe('a\\\\b');
+    });
+
+    it('should handle empty string', () => {
+      expect(escapeShellPath('')).toBe('');
+    });
+  });
+
+  describe('resolvePathCompletions', () => {
+    let tmpDir: string;
+
+    afterEach(async () => {
+      if (tmpDir) {
+        await cleanupTmpDir(tmpDir);
+      }
+    });
+
+    it('should list directory contents for empty partial', async () => {
+      const structure: FileSystemStructure = {
+        'file.txt': '',
+        subdir: {},
+      };
+      tmpDir = await createTmpDir(structure);
+
+      const results = await resolvePathCompletions('', tmpDir);
+      const values = results.map((s) => s.label);
+      expect(values).toContain('subdir/');
+      expect(values).toContain('file.txt');
+    });
+
+    it('should filter by prefix', async () => {
+      const structure: FileSystemStructure = {
+        'abc.txt': '',
+        'def.txt': '',
+      };
+      tmpDir = await createTmpDir(structure);
+
+      const results = await resolvePathCompletions('a', tmpDir);
+      expect(results).toHaveLength(1);
+      expect(results[0].label).toBe('abc.txt');
+    });
+
+    it('should match case-insensitively', async () => {
+      const structure: FileSystemStructure = {
+        Desktop: {},
+      };
+      tmpDir = await createTmpDir(structure);
+
+      const results = await resolvePathCompletions('desk', tmpDir);
+      expect(results).toHaveLength(1);
+      expect(results[0].label).toBe('Desktop/');
+    });
+
+    it('should append trailing slash to directories', async () => {
+      const structure: FileSystemStructure = {
+        mydir: {},
+        'myfile.txt': '',
+      };
+      tmpDir = await createTmpDir(structure);
+
+      const results = await resolvePathCompletions('my', tmpDir);
+      const dirSuggestion = results.find((s) => s.label.startsWith('mydir'));
+      expect(dirSuggestion?.label).toBe('mydir/');
+      expect(dirSuggestion?.description).toBe('directory');
+    });
+
+    it('should hide dotfiles by default', async () => {
+      const structure: FileSystemStructure = {
+        '.hidden': '',
+        visible: '',
+      };
+      tmpDir = await createTmpDir(structure);
+
+      const results = await resolvePathCompletions('', tmpDir);
+      const labels = results.map((s) => s.label);
+      expect(labels).not.toContain('.hidden');
+      expect(labels).toContain('visible');
+    });
+
+    it('should show dotfiles when query starts with a dot', async () => {
+      const structure: FileSystemStructure = {
+        '.hidden': '',
+        '.bashrc': '',
+        visible: '',
+      };
+      tmpDir = await createTmpDir(structure);
+
+      const results = await resolvePathCompletions('.h', tmpDir);
+      const labels = results.map((s) => s.label);
+      expect(labels).toContain('.hidden');
+    });
+
+    it('should show dotfiles in the current directory when query is exactly "."', async () => {
+      const structure: FileSystemStructure = {
+        '.hidden': '',
+        '.bashrc': '',
+        visible: '',
+      };
+      tmpDir = await createTmpDir(structure);
+
+      const results = await resolvePathCompletions('.', tmpDir);
+      const labels = results.map((s) => s.label);
+      expect(labels).toContain('.hidden');
+      expect(labels).toContain('.bashrc');
+      expect(labels).not.toContain('visible');
+    });
+
+    it('should handle dotfile completions within a subdirectory', async () => {
+      const structure: FileSystemStructure = {
+        subdir: {
+          '.secret': '',
+          'public.txt': '',
+        },
+      };
+      tmpDir = await createTmpDir(structure);
+
+      const results = await resolvePathCompletions('subdir/.', tmpDir);
+      const labels = results.map((s) => s.label);
+      expect(labels).toContain('.secret');
+      expect(labels).not.toContain('public.txt');
+    });
+
+    it('should strip leading quotes to resolve inner directory contents', async () => {
+      const structure: FileSystemStructure = {
+        src: {
+          'index.ts': '',
+        },
+      };
+      tmpDir = await createTmpDir(structure);
+
+      const results = await resolvePathCompletions('"src/', tmpDir);
+      expect(results).toHaveLength(1);
+      expect(results[0].label).toBe('index.ts');
+
+      const resultsSingleQuote = await resolvePathCompletions("'src/", tmpDir);
+      expect(resultsSingleQuote).toHaveLength(1);
+      expect(resultsSingleQuote[0].label).toBe('index.ts');
+    });
+
+    it('should properly escape resolutions with spaces inside stripped quote queries', async () => {
+      const structure: FileSystemStructure = {
+        'Folder With Spaces': {},
+      };
+      tmpDir = await createTmpDir(structure);
+
+      const results = await resolvePathCompletions('"Fo', tmpDir);
+      expect(results).toHaveLength(1);
+      expect(results[0].label).toBe('Folder With Spaces/');
+      expect(results[0].value).toBe(escapeShellPath('Folder With Spaces/'));
+    });
+
+    it('should return empty array for non-existent directory', async () => {
+      const results = await resolvePathCompletions(
+        '/nonexistent/path/foo',
+        '/tmp',
+      );
+      expect(results).toEqual([]);
+    });
+
+    it('should handle tilde expansion', async () => {
+      // Just ensure ~ doesn't throw
+      const results = await resolvePathCompletions('~/', '/tmp');
+      // We can't assert specific files since it depends on the test runner's home
+      expect(Array.isArray(results)).toBe(true);
+    });
+
+    it('should escape special characters in results', async () => {
+      const structure: FileSystemStructure = {
+        'my file.txt': '',
+      };
+      tmpDir = await createTmpDir(structure);
+
+      const results = await resolvePathCompletions('my', tmpDir);
+      expect(results).toHaveLength(1);
+      expect(results[0].value).toBe('my\\ file.txt');
+    });
+
+    it('should sort directories before files', async () => {
+      const structure: FileSystemStructure = {
+        'b-file.txt': '',
+        'a-dir': {},
+      };
+      tmpDir = await createTmpDir(structure);
+
+      const results = await resolvePathCompletions('', tmpDir);
+      expect(results[0].description).toBe('directory');
+      expect(results[1].description).toBe('file');
+    });
+  });
+
+  describe('scanPathExecutables', () => {
+    it('should return an array of executables', async () => {
+      const results = await scanPathExecutables();
+      expect(Array.isArray(results)).toBe(true);
+      // Very basic sanity check: common commands should be found
+      if (process.platform !== 'win32') {
+        expect(results).toContain('ls');
+      } else {
+        expect(results).toContain('dir');
+        expect(results).toContain('cls');
+        expect(results).toContain('copy');
+      }
+    });
+
+    it('should support abort signal', async () => {
+      const controller = new AbortController();
+      controller.abort();
+      const results = await scanPathExecutables(controller.signal);
+      // May return empty or partial depending on timing
+      expect(Array.isArray(results)).toBe(true);
+    });
+
+    it('should handle empty PATH', async () => {
+      vi.stubEnv('PATH', '');
+      const results = await scanPathExecutables();
+      expect(results).toEqual([]);
+      vi.unstubAllEnvs();
+    });
+  });
+});

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

@@ -0,0 +1,620 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { useEffect, useRef, useCallback, useMemo } from 'react';
+import * as fs from 'node:fs/promises';
+import * as path from 'node:path';
+import * as os from 'node:os';
+import type { Suggestion } from '../components/SuggestionsDisplay.js';
+import { debugLogger } from '@google/gemini-cli-core';
+import { getArgumentCompletions } from './shell-completions/index.js';
+
+/**
+ * Maximum number of suggestions to return to avoid freezing the React Ink UI.
+ */
+const MAX_SHELL_SUGGESTIONS = 100;
+
+/**
+ * Debounce interval (ms) for file system completions.
+ */
+const FS_COMPLETION_DEBOUNCE_MS = 50;
+
+// Backslash-quote shell metacharacters on non-Windows platforms.
+
+// On Unix, backslash-quote shell metacharacters (spaces, parens, etc.).
+// On Windows, cmd.exe doesn't use backslash-quoting and `\` is the path
+// separator, so we leave the path as-is.
+const UNIX_SHELL_SPECIAL_CHARS = /[ \t\n\r'"()&|;<>!#$`{}[\]*?\\]/g;
+
+/**
+ * Escapes special shell characters in a path segment.
+ */
+export function escapeShellPath(segment: string): string {
+  if (process.platform === 'win32') {
+    return segment;
+  }
+  return segment.replace(UNIX_SHELL_SPECIAL_CHARS, '\\$&');
+}
+
+export interface TokenInfo {
+  /** The raw token text (without surrounding quotes but with internal escapes). */
+  token: string;
+  /** Offset in the original line where this token begins. */
+  start: number;
+  /** Offset in the original line where this token ends (exclusive). */
+  end: number;
+  /** Whether this is the first token (command position). */
+  isFirstToken: boolean;
+  /** The fully built list of tokens parsing the string. */
+  tokens: string[];
+  /** The index in the tokens list where the cursor lies. */
+  cursorIndex: number;
+  /** The command token (always tokens[0] if length > 0, otherwise empty string) */
+  commandToken: string;
+}
+
+export function getTokenAtCursor(
+  line: string,
+  cursorCol: number,
+): TokenInfo | null {
+  const tokensInfo: Array<{ token: string; start: number; end: number }> = [];
+  let i = 0;
+
+  while (i < line.length) {
+    // Skip whitespace
+    if (line[i] === ' ' || line[i] === '\t') {
+      i++;
+      continue;
+    }
+
+    const tokenStart = i;
+    let token = '';
+
+    while (i < line.length) {
+      const ch = line[i];
+
+      // Backslash escape: consume the next char literally
+      if (ch === '\\' && i + 1 < line.length) {
+        token += line[i + 1];
+        i += 2;
+        continue;
+      }
+
+      // Single-quoted string
+      if (ch === "'") {
+        i++; // skip opening quote
+        while (i < line.length && line[i] !== "'") {
+          token += line[i];
+          i++;
+        }
+        if (i < line.length) i++; // skip closing quote
+        continue;
+      }
+
+      // Double-quoted string
+      if (ch === '"') {
+        i++; // skip opening quote
+        while (i < line.length && line[i] !== '"') {
+          if (line[i] === '\\' && i + 1 < line.length) {
+            token += line[i + 1];
+            i += 2;
+          } else {
+            token += line[i];
+            i++;
+          }
+        }
+        if (i < line.length) i++; // skip closing quote
+        continue;
+      }
+
+      // Unquoted whitespace ends the token
+      if (ch === ' ' || ch === '\t') {
+        break;
+      }
+
+      token += ch;
+      i++;
+    }
+
+    tokensInfo.push({ token, start: tokenStart, end: i });
+  }
+
+  const rawTokens = tokensInfo.map((t) => t.token);
+  const commandToken = rawTokens.length > 0 ? rawTokens[0] : '';
+
+  if (tokensInfo.length === 0) {
+    return {
+      token: '',
+      start: cursorCol,
+      end: cursorCol,
+      isFirstToken: true,
+      tokens: [''],
+      cursorIndex: 0,
+      commandToken: '',
+    };
+  }
+
+  // Find the token that contains or is immediately adjacent to the cursor
+  for (let idx = 0; idx < tokensInfo.length; idx++) {
+    const t = tokensInfo[idx];
+    if (cursorCol >= t.start && cursorCol <= t.end) {
+      return {
+        token: t.token,
+        start: t.start,
+        end: t.end,
+        isFirstToken: idx === 0,
+        tokens: rawTokens,
+        cursorIndex: idx,
+        commandToken,
+      };
+    }
+  }
+
+  // Cursor is past all tokens — treat as starting a new token at cursor position
+  // (useful when the user types a space and then presses Tab)
+  return {
+    token: '',
+    start: cursorCol,
+    end: cursorCol,
+    isFirstToken: tokensInfo.length === 0,
+    tokens: [...rawTokens, ''],
+    cursorIndex: rawTokens.length,
+    commandToken,
+  };
+}
+
+export async function scanPathExecutables(
+  signal?: AbortSignal,
+): Promise<string[]> {
+  const pathEnv = process.env['PATH'] ?? '';
+  const dirs = pathEnv.split(path.delimiter).filter(Boolean);
+  const isWindows = process.platform === 'win32';
+  const pathExtList = isWindows
+    ? (process.env['PATHEXT'] ?? '.EXE;.CMD;.BAT;.COM')
+        .split(';')
+        .filter(Boolean)
+        .map((e) => e.toLowerCase())
+    : [];
+
+  const seen = new Set<string>();
+  const executables: string[] = [];
+
+  // Add Windows shell built-ins
+  if (isWindows) {
+    const builtins = [
+      'assoc',
+      'break',
+      'call',
+      'cd',
+      'chcp',
+      'chdir',
+      'cls',
+      'color',
+      'copy',
+      'date',
+      'del',
+      'dir',
+      'echo',
+      'endlocal',
+      'erase',
+      'exit',
+      'for',
+      'ftype',
+      'goto',
+      'if',
+      'md',
+      'mkdir',
+      'mklink',
+      'move',
+      'path',
+      'pause',
+      'popd',
+      'prompt',
+      'pushd',
+      'rd',
+      'rem',
+      'ren',
+      'rename',
+      'rmdir',
+      'set',
+      'setlocal',
+      'shift',
+      'start',
+      'time',
+      'title',
+      'type',
+      'ver',
+      'verify',
+      'vol',
+    ];
+    for (const builtin of builtins) {
+      seen.add(builtin);
+      executables.push(builtin);
+    }
+  }
+
+  const dirResults = await Promise.all(
+    dirs.map(async (dir) => {
+      if (signal?.aborted) return [];
+      try {
+        const entries = await fs.readdir(dir, { withFileTypes: true });
+        const validEntries: string[] = [];
+
+        // Check executability in parallel (batched per directory)
+        await Promise.all(
+          entries.map(async (entry) => {
+            if (signal?.aborted) return;
+            if (!entry.isFile() && !entry.isSymbolicLink()) return;
+
+            const name = entry.name;
+            if (isWindows) {
+              const ext = path.extname(name).toLowerCase();
+              if (pathExtList.length > 0 && !pathExtList.includes(ext)) return;
+            }
+
+            try {
+              await fs.access(
+                path.join(dir, name),
+                fs.constants.R_OK | fs.constants.X_OK,
+              );
+              validEntries.push(name);
+            } catch {
+              // Not executable — skip
+            }
+          }),
+        );
+
+        return validEntries;
+      } catch {
+        // EACCES, ENOENT, etc. — skip this directory
+        return [];
+      }
+    }),
+  );
+
+  for (const names of dirResults) {
+    for (const name of names) {
+      if (!seen.has(name)) {
+        seen.add(name);
+        executables.push(name);
+      }
+    }
+  }
+
+  executables.sort();
+  return executables;
+}
+
+function expandTilde(inputPath: string): [string, boolean] {
+  if (
+    inputPath === '~' ||
+    inputPath.startsWith('~/') ||
+    inputPath.startsWith('~' + path.sep)
+  ) {
+    return [path.join(os.homedir(), inputPath.slice(1)), true];
+  }
+  return [inputPath, false];
+}
+
+export async function resolvePathCompletions(
+  partial: string,
+  cwd: string,
+  signal?: AbortSignal,
+): Promise<Suggestion[]> {
+  if (partial == null) return [];
+
+  // Input Sanitization
+  let strippedPartial = partial;
+  if (strippedPartial.startsWith('"') || strippedPartial.startsWith("'")) {
+    strippedPartial = strippedPartial.slice(1);
+  }
+  if (strippedPartial.endsWith('"') || strippedPartial.endsWith("'")) {
+    strippedPartial = strippedPartial.slice(0, -1);
+  }
+
+  // Normalize separators \ to /
+  const normalizedPartial = strippedPartial.replace(/\\/g, '/');
+
+  const [expandedPartial, didExpandTilde] = expandTilde(normalizedPartial);
+
+  // Directory Detection
+  const endsWithSep =
+    normalizedPartial.endsWith('/') || normalizedPartial === '';
+  const dirToRead = endsWithSep
+    ? path.resolve(cwd, expandedPartial)
+    : path.resolve(cwd, path.dirname(expandedPartial));
+
+  const prefix = endsWithSep ? '' : path.basename(expandedPartial);
+  const prefixLower = prefix.toLowerCase();
+
+  const showDotfiles = prefix.startsWith('.');
+
+  let entries: Array<import('node:fs').Dirent>;
+  try {
+    if (signal?.aborted) return [];
+    entries = await fs.readdir(dirToRead, { withFileTypes: true });
+  } catch {
+    // EACCES, ENOENT, etc.
+    return [];
+  }
+
+  if (signal?.aborted) return [];
+
+  const suggestions: Suggestion[] = [];
+  for (const entry of entries) {
+    if (signal?.aborted) break;
+
+    const name = entry.name;
+
+    // Hide dotfiles unless query starts with '.'
+    if (name.startsWith('.') && !showDotfiles) continue;
+
+    // Case-insensitive matching
+    if (!name.toLowerCase().startsWith(prefixLower)) continue;
+
+    const isDir = entry.isDirectory();
+    const displayName = isDir ? name + '/' : name;
+
+    // Build the completion value relative to what the user typed
+    let completionValue: string;
+    if (endsWithSep) {
+      completionValue = normalizedPartial + displayName;
+    } else {
+      const parentPart = normalizedPartial.slice(
+        0,
+        normalizedPartial.length - path.basename(normalizedPartial).length,
+      );
+      completionValue = parentPart + displayName;
+    }
+
+    // Restore tilde if we expanded it
+    if (didExpandTilde) {
+      const homeDir = os.homedir().replace(/\\/g, '/');
+      if (completionValue.startsWith(homeDir)) {
+        completionValue = '~' + completionValue.slice(homeDir.length);
+      }
+    }
+
+    // Output formatting: Escape special characters in the completion value
+    // Since normalizedPartial stripped quotes, we escape the value directly.
+    const escapedValue = escapeShellPath(completionValue);
+
+    suggestions.push({
+      label: displayName,
+      value: escapedValue,
+      description: isDir ? 'directory' : 'file',
+    });
+
+    if (suggestions.length >= MAX_SHELL_SUGGESTIONS) break;
+  }
+
+  // Sort: directories first, then alphabetically
+  suggestions.sort((a, b) => {
+    const aIsDir = a.description === 'directory';
+    const bIsDir = b.description === 'directory';
+    if (aIsDir !== bIsDir) return aIsDir ? -1 : 1;
+    return a.label.localeCompare(b.label);
+  });
+
+  return suggestions;
+}
+
+export interface UseShellCompletionProps {
+  /** Whether shell completion is active. */
+  enabled: boolean;
+  /** The current line text. */
+  line: string;
+  /** The current cursor column. */
+  cursorCol: number;
+  /** The current working directory for path resolution. */
+  cwd: string;
+  /** Callback to set suggestions on the parent state. */
+  setSuggestions: (suggestions: Suggestion[]) => void;
+  /** Callback to set loading state on the parent. */
+  setIsLoadingSuggestions: (isLoading: boolean) => void;
+}
+
+export interface UseShellCompletionReturn {
+  completionStart: number;
+  completionEnd: number;
+  query: string;
+}
+
+export function useShellCompletion({
+  enabled,
+  line,
+  cursorCol,
+  cwd,
+  setSuggestions,
+  setIsLoadingSuggestions,
+}: UseShellCompletionProps): UseShellCompletionReturn {
+  const pathCachePromiseRef = useRef<Promise<string[]> | null>(null);
+  const pathEnvRef = useRef<string>(process.env['PATH'] ?? '');
+  const abortRef = useRef<AbortController | null>(null);
+  const debounceRef = useRef<NodeJS.Timeout | null>(null);
+
+  const tokenInfo = useMemo(
+    () => (enabled ? getTokenAtCursor(line, cursorCol) : null),
+    [enabled, line, cursorCol],
+  );
+
+  const {
+    token: query = '',
+    start: completionStart = -1,
+    end: completionEnd = -1,
+    isFirstToken: isCommandPosition = false,
+    tokens = [],
+    cursorIndex = -1,
+    commandToken = '',
+  } = tokenInfo || {};
+
+  // Invalidate PATH cache when $PATH changes
+  useEffect(() => {
+    const currentPath = process.env['PATH'] ?? '';
+    if (currentPath !== pathEnvRef.current) {
+      pathCachePromiseRef.current = null;
+      pathEnvRef.current = currentPath;
+    }
+  });
+
+  const performCompletion = useCallback(async () => {
+    if (!enabled || !tokenInfo) {
+      setSuggestions([]);
+      return;
+    }
+
+    // Skip flags
+    if (query.startsWith('-')) {
+      setSuggestions([]);
+      return;
+    }
+
+    // Cancel any in-flight request
+    if (abortRef.current) {
+      abortRef.current.abort();
+    }
+    const controller = new AbortController();
+    abortRef.current = controller;
+    const { signal } = controller;
+
+    try {
+      let results: Suggestion[];
+
+      if (isCommandPosition) {
+        setIsLoadingSuggestions(true);
+
+        if (!pathCachePromiseRef.current) {
+          // We don't pass the signal here because we want the cache to finish
+          // even if this specific completion request is aborted.
+          pathCachePromiseRef.current = scanPathExecutables();
+        }
+
+        const executables = await pathCachePromiseRef.current;
+        if (signal.aborted) return;
+
+        const queryLower = query.toLowerCase();
+        results = executables
+          .filter((cmd) => cmd.toLowerCase().startsWith(queryLower))
+          .sort((a, b) => {
+            // Prioritize shorter commands as they are likely common built-ins
+            if (a.length !== b.length) {
+              return a.length - b.length;
+            }
+            return a.localeCompare(b);
+          })
+          .slice(0, MAX_SHELL_SUGGESTIONS)
+          .map((cmd) => ({
+            label: cmd,
+            value: escapeShellPath(cmd),
+            description: 'command',
+          }));
+      } else {
+        const argumentCompletions = await getArgumentCompletions(
+          commandToken,
+          tokens,
+          cursorIndex,
+          cwd,
+          signal,
+        );
+
+        if (signal.aborted) return;
+
+        if (argumentCompletions?.exclusive) {
+          results = argumentCompletions.suggestions;
+        } else {
+          const pathSuggestions = await resolvePathCompletions(
+            query,
+            cwd,
+            signal,
+          );
+          if (signal.aborted) return;
+
+          results = [
+            ...(argumentCompletions?.suggestions ?? []),
+            ...pathSuggestions,
+          ].slice(0, MAX_SHELL_SUGGESTIONS);
+        }
+      }
+
+      if (signal.aborted) return;
+
+      setSuggestions(results);
+    } catch (error) {
+      if (
+        !(
+          signal.aborted ||
+          (error instanceof Error && error.name === 'AbortError')
+        )
+      ) {
+        debugLogger.warn(
+          `[WARN] shell completion failed: ${error instanceof Error ? error.message : String(error)}`,
+        );
+      }
+      if (!signal.aborted) {
+        setSuggestions([]);
+      }
+    } finally {
+      if (!signal.aborted) {
+        setIsLoadingSuggestions(false);
+      }
+    }
+  }, [
+    enabled,
+    tokenInfo,
+    query,
+    isCommandPosition,
+    tokens,
+    cursorIndex,
+    commandToken,
+    cwd,
+    setSuggestions,
+    setIsLoadingSuggestions,
+  ]);
+
+  useEffect(() => {
+    if (!enabled) {
+      setSuggestions([]);
+      setIsLoadingSuggestions(false);
+    }
+  }, [enabled, setSuggestions, setIsLoadingSuggestions]);
+
+  // Debounced effect to trigger completion
+  useEffect(() => {
+    if (!enabled) return;
+
+    if (debounceRef.current) {
+      clearTimeout(debounceRef.current);
+    }
+
+    debounceRef.current = setTimeout(() => {
+      // eslint-disable-next-line @typescript-eslint/no-floating-promises
+      performCompletion();
+    }, FS_COMPLETION_DEBOUNCE_MS);
+
+    return () => {
+      if (debounceRef.current) {
+        clearTimeout(debounceRef.current);
+      }
+    };
+  }, [enabled, performCompletion]);
+
+  // Cleanup on unmount
+  useEffect(
+    () => () => {
+      abortRef.current?.abort();
+      if (debounceRef.current) {
+        clearTimeout(debounceRef.current);
+      }
+    },
+    [],
+  );
+
+  return {
+    completionStart,
+    completionEnd,
+    query,
+  };
+}