feat: Support Alt+key combinations (google-gemini#10767)

Author: srivatsj

packages/cli/src/ui/contexts/KeypressContext.test.tsx

@@ -956,3 +956,127 @@ describe('Drag and Drop Handling', () => {
     });
   });
 });
+
+describe('Terminal-specific Alt+key combinations', () => {
+  let stdin: MockStdin;
+  const mockSetRawMode = vi.fn();
+
+  const wrapper = ({ children }: { children: React.ReactNode }) => (
+    <KeypressProvider kittyProtocolEnabled={true}>{children}</KeypressProvider>
+  );
+
+  beforeEach(() => {
+    vi.clearAllMocks();
+    stdin = new MockStdin();
+    (useStdin as Mock).mockReturnValue({
+      stdin,
+      setRawMode: mockSetRawMode,
+    });
+  });
+
+  // Terminals to test
+  const terminals = ['iTerm2', 'Ghostty', 'MacTerminal', 'VSCodeTerminal'];
+
+  // Key mappings: letter -> [keycode, accented character, shouldHaveMeta]
+  // Note: µ (mu) is sent with meta:false on iTerm2/VSCode
+  const keys: Record<string, [number, string, boolean]> = {
+    a: [97, 'å', true],
+    o: [111, 'ø', true],
+    m: [109, 'µ', false],
+  };
+
+  it.each(
+    terminals.flatMap((terminal) =>
+      Object.entries(keys).map(
+        ([key, [keycode, accentedChar, shouldHaveMeta]]) => {
+          if (terminal === 'Ghostty') {
+            // Ghostty uses kitty protocol sequences
+            return {
+              terminal,
+              key,
+              kittySequence: `\x1b[${keycode};3u`,
+              expected: {
+                name: key,
+                ctrl: false,
+                meta: true,
+                shift: false,
+                paste: false,
+                kittyProtocol: true,
+              },
+            };
+          } else if (terminal === 'MacTerminal') {
+            // Mac Terminal sends ESC + letter
+            return {
+              terminal,
+              key,
+              input: {
+                sequence: `\x1b${key}`,
+                name: key,
+                ctrl: false,
+                meta: true,
+                shift: false,
+                paste: false,
+              },
+              expected: {
+                sequence: `\x1b${key}`,
+                name: key,
+                ctrl: false,
+                meta: true,
+                shift: false,
+                paste: false,
+              },
+            };
+          } else {
+            // iTerm2 and VSCode send accented characters (å, ø, µ)
+            // Note: µ comes with meta:false but gets converted to m with meta:true
+            return {
+              terminal,
+              key,
+              input: {
+                name: key,
+                ctrl: false,
+                meta: shouldHaveMeta,
+                shift: false,
+                paste: false,
+                sequence: accentedChar,
+              },
+              expected: {
+                name: key,
+                ctrl: false,
+                meta: true, // Always expect meta:true after conversion
+                shift: false,
+                paste: false,
+                sequence: accentedChar,
+              },
+            };
+          }
+        },
+      ),
+    ),
+  )(
+    'should handle Alt+$key in $terminal',
+    ({
+      kittySequence,
+      input,
+      expected,
+    }: {
+      kittySequence?: string;
+      input?: Partial<Key>;
+      expected: Partial<Key>;
+    }) => {
+      const keyHandler = vi.fn();
+      const { result } = renderHook(() => useKeypressContext(), { wrapper });
+      act(() => result.current.subscribe(keyHandler));
+
+      if (kittySequence) {
+        act(() => stdin.sendKittySequence(kittySequence));
+      } else if (input) {
+        act(() => stdin.pressKey(input));
+      }
+
+      expect(keyHandler).toHaveBeenCalledWith(
+        expect.objectContaining(expected),
+      );
+    },
+  );
+});

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

@@ -45,6 +45,36 @@ export const DRAG_COMPLETION_TIMEOUT_MS = 100; // Broadcast full path after 100m
 export const SINGLE_QUOTE = "'";
 export const DOUBLE_QUOTE = '"';
 
+const ALT_KEY_CHARACTER_MAP: Record<string, string> = {
+  '\u00E5': 'a',
+  '\u222B': 'b',
+  '\u00E7': 'c',
+  '\u2202': 'd',
+  '\u00B4': 'e',
+  '\u0192': 'f',
+  '\u00A9': 'g',
+  '\u02D9': 'h',
+  '\u02C6': 'i',
+  '\u2206': 'j',
+  '\u02DA': 'k',
+  '\u00AC': 'l',
+  '\u00B5': 'm',
+  '\u02DC': 'n',
+  '\u00F8': 'o',
+  '\u03C0': 'p',
+  '\u0153': 'q',
+  '\u00AE': 'r',
+  '\u00DF': 's',
+  '\u2020': 't',
+  '\u00A8': 'u',
+  '\u221A': 'v',
+  '\u2211': 'w',
+  '\u2248': 'x',
+  '\u00A5': 'y',
+  '\\': 'y',
+  '\u03A9': 'z',
+};
+
 export interface Key {
   name: string;
   ctrl: boolean;
@@ -327,17 +357,17 @@ export function KeypressProvider({
           };
         }
 
-        // Ctrl+letters
+        // Ctrl+letters and Alt+letters
         if (
-          ctrl &&
+          (ctrl || alt) &&
           keyCode >= 'a'.charCodeAt(0) &&
           keyCode <= 'z'.charCodeAt(0)
         ) {
           const letter = String.fromCharCode(keyCode);
           return {
             key: {
               name: letter,
-              ctrl: true,
+              ctrl,
               meta: alt,
               shift,
               paste: false,
@@ -435,6 +465,19 @@ export function KeypressProvider({
         return;
       }
 
+      const mappedLetter = ALT_KEY_CHARACTER_MAP[key.sequence];
+      if (mappedLetter && !key.meta) {
+        broadcast({
+          name: mappedLetter,
+          ctrl: false,
+          meta: true,
+          shift: false,
+          paste: isPaste,
+          sequence: key.sequence,
+        });
+        return;
+      }
+
       if (key.name === 'return' && waitingForEnterAfterBackslash) {
         if (backslashTimeout) {
           clearTimeout(backslashTimeout);