Inline thinking bubbles with summary/full modes (#18033)

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

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

@@ -0,0 +1,15 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import type { LoadedSettings } from '../../config/settings.js';
+
+export type InlineThinkingMode = 'off' | 'full';
+
+export function getInlineThinkingMode(
+  settings: LoadedSettings,
+): InlineThinkingMode {
+  return settings.merged.ui?.inlineThinkingMode ?? 'off';
+}

packages/cli/src/ui/utils/terminalUtils.test.ts

@@ -5,11 +5,15 @@
  */
 
 import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest';
-import { isITerm2, resetITerm2Cache } from './terminalUtils.js';
+import { isITerm2, resetITerm2Cache, shouldUseEmoji } from './terminalUtils.js';
 
 describe('terminalUtils', () => {
   beforeEach(() => {
     vi.stubEnv('TERM_PROGRAM', '');
+    vi.stubEnv('LC_ALL', '');
+    vi.stubEnv('LC_CTYPE', '');
+    vi.stubEnv('LANG', '');
+    vi.stubEnv('TERM', '');
     resetITerm2Cache();
   });
 
@@ -18,25 +22,56 @@ describe('terminalUtils', () => {
     vi.restoreAllMocks();
   });
 
-  it('should detect iTerm2 via TERM_PROGRAM', () => {
-    vi.stubEnv('TERM_PROGRAM', 'iTerm.app');
-    expect(isITerm2()).toBe(true);
+  describe('isITerm2', () => {
+    it('should detect iTerm2 via TERM_PROGRAM', () => {
+      vi.stubEnv('TERM_PROGRAM', 'iTerm.app');
+      expect(isITerm2()).toBe(true);
+    });
+
+    it('should return false if not iTerm2', () => {
+      vi.stubEnv('TERM_PROGRAM', 'vscode');
+      expect(isITerm2()).toBe(false);
+    });
+
+    it('should cache the result', () => {
+      vi.stubEnv('TERM_PROGRAM', 'iTerm.app');
+      expect(isITerm2()).toBe(true);
+
+      // Change env but should still be true due to cache
+      vi.stubEnv('TERM_PROGRAM', 'vscode');
+      expect(isITerm2()).toBe(true);
+
+      resetITerm2Cache();
+      expect(isITerm2()).toBe(false);
+    });
   });
 
-  it('should return false if not iTerm2', () => {
-    vi.stubEnv('TERM_PROGRAM', 'vscode');
-    expect(isITerm2()).toBe(false);
-  });
+  describe('shouldUseEmoji', () => {
+    it('should return true when UTF-8 is supported', () => {
+      vi.stubEnv('LANG', 'en_US.UTF-8');
+      expect(shouldUseEmoji()).toBe(true);
+    });
 
-  it('should cache the result', () => {
-    vi.stubEnv('TERM_PROGRAM', 'iTerm.app');
-    expect(isITerm2()).toBe(true);
+    it('should return true when utf8 (no hyphen) is supported', () => {
+      vi.stubEnv('LANG', 'en_US.utf8');
+      expect(shouldUseEmoji()).toBe(true);
+    });
 
-    // Change env but should still be true due to cache
-    vi.stubEnv('TERM_PROGRAM', 'vscode');
-    expect(isITerm2()).toBe(true);
+    it('should check LC_ALL first', () => {
+      vi.stubEnv('LC_ALL', 'en_US.UTF-8');
+      vi.stubEnv('LANG', 'C');
+      expect(shouldUseEmoji()).toBe(true);
+    });
 
-    resetITerm2Cache();
-    expect(isITerm2()).toBe(false);
+    it('should return false when UTF-8 is not supported', () => {
+      vi.stubEnv('LANG', 'C');
+      expect(shouldUseEmoji()).toBe(false);
+    });
+
+    it('should return false on linux console (TERM=linux)', () => {
+      vi.stubEnv('LANG', 'en_US.UTF-8');
+      vi.stubEnv('TERM', 'linux');
+      expect(shouldUseEmoji()).toBe(false);
+    });
   });
 });

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

@@ -43,3 +43,25 @@ export function isITerm2(): boolean {
 export function resetITerm2Cache(): void {
   cachedIsITerm2 = undefined;
 }
+
+/**
+ * Returns true if the terminal likely supports emoji.
+ */
+export function shouldUseEmoji(): boolean {
+  const locale = (
+    process.env['LC_ALL'] ||
+    process.env['LC_CTYPE'] ||
+    process.env['LANG'] ||
+    ''
+  ).toLowerCase();
+  const supportsUtf8 = locale.includes('utf-8') || locale.includes('utf8');
+  if (!supportsUtf8) {
+    return false;
+  }
+
+  if (process.env['TERM'] === 'linux') {
+    return false;
+  }
+
+  return true;
+}