diff --git a/frontend/src/lib/__tests__/keyboard-guards.test.ts b/frontend/src/lib/__tests__/keyboard-guards.test.ts
new file mode 100644
index 00000000..b4a5a30f
--- /dev/null
+++ b/frontend/src/lib/__tests__/keyboard-guards.test.ts
@@ -0,0 +1,87 @@
+/**
+ * Unit tests for isInputFocused, the shared guard both global hotkey systems
+ * use to bail when the user is typing in a field.
+ *
+ * Regression guard for #1410: Monaco's Chromium EditContext input surface is a
+ * plain focusable <div class="native-edit-context"> inside .monaco-editor, not a
+ * <textarea> or contentEditable element, so the tag/contentEditable checks miss
+ * it and single-key hotkeys (a/h/u/p/b) fired while editing a compose file in
+ * Chrome (Safari falls back to a hidden <textarea> and was unaffected).
+ *
+ * activeElement is stubbed with real DOM nodes so tagName, isContentEditable, and
+ * closest() all run their real logic, while staying free of jsdom's unreliable
+ * .focus() / isContentEditable handling on detached elements.
+ */
+import { describe, it, expect, afterEach } from 'vitest';
+import { isInputFocused } from '../keyboard-guards';
+
+function stubActiveElement(el: Element | null): void {
+  Object.defineProperty(document, 'activeElement', { configurable: true, get: () => el });
+}
+
+afterEach(() => {
+  // Drop the own-property shadow so jsdom's native activeElement getter returns.
+  Reflect.deleteProperty(document, 'activeElement');
+});
+
+describe('isInputFocused', () => {
+  it('returns false when nothing is focused', () => {
+    stubActiveElement(null);
+    expect(isInputFocused()).toBe(false);
+  });
+
+  it('returns true for a focused <input>', () => {
+    stubActiveElement(document.createElement('input'));
+    expect(isInputFocused()).toBe(true);
+  });
+
+  it('returns true for a focused <textarea>', () => {
+    stubActiveElement(document.createElement('textarea'));
+    expect(isInputFocused()).toBe(true);
+  });
+
+  it('returns true for a contentEditable element', () => {
+    const div = document.createElement('div');
+    Object.defineProperty(div, 'isContentEditable', { value: true });
+    stubActiveElement(div);
+    expect(isInputFocused()).toBe(true);
+  });
+
+  it('returns false for a focused non-editable element', () => {
+    stubActiveElement(document.createElement('button'));
+    expect(isInputFocused()).toBe(false);
+  });
+
+  it('returns true for focus inside the Monaco editor container (#1410)', () => {
+    const editor = document.createElement('div');
+    editor.className = 'monaco-editor';
+    const editContext = document.createElement('div');
+    editContext.className = 'native-edit-context';
+    editor.appendChild(editContext);
+    document.body.appendChild(editor);
+    stubActiveElement(editContext);
+    try {
+      expect(isInputFocused()).toBe(true);
+    } finally {
+      document.body.removeChild(editor);
+    }
+  });
+
+  it('returns true for any descendant of the Monaco editor, not just the edit-context node', () => {
+    // Pins the deliberate whole-container semantics: focus anywhere inside
+    // .monaco-editor counts, so narrowing the guard to a specific inner class
+    // would regress.
+    const editor = document.createElement('div');
+    editor.className = 'monaco-editor';
+    const viewLine = document.createElement('div');
+    viewLine.className = 'view-line';
+    editor.appendChild(viewLine);
+    document.body.appendChild(editor);
+    stubActiveElement(viewLine);
+    try {
+      expect(isInputFocused()).toBe(true);
+    } finally {
+      document.body.removeChild(editor);
+    }
+  });
+});
diff --git a/frontend/src/lib/keyboard-guards.ts b/frontend/src/lib/keyboard-guards.ts
index 0174f37f..8f0c36eb 100644
--- a/frontend/src/lib/keyboard-guards.ts
+++ b/frontend/src/lib/keyboard-guards.ts
@@ -2,7 +2,11 @@ export function isInputFocused(): boolean {
   const el = document.activeElement as HTMLElement | null;
   if (!el) return false;
   const tag = el.tagName;
-  return tag === 'INPUT' || tag === 'TEXTAREA' || el.isContentEditable;
+  if (tag === 'INPUT' || tag === 'TEXTAREA' || el.isContentEditable) return true;
+  // Monaco's EditContext surface (Chromium) is a plain focusable <div>, not a textarea or
+  // contentEditable element, so the checks above miss it. Treat any focus inside the editor
+  // container as input focus, matching the textarea fallback other browsers already get.
+  return !!el.closest('.monaco-editor');
 }
 
 export function isPaletteOpen(): boolean {