fix: preserve undo history when pasting into the chat input

src/components/__test__/chat-item/prompt-text-input.spec.ts

@@ -112,7 +112,44 @@ describe('prompt-text-input', () => {
     expect(inputElement?.getAttribute('placeholder')).toBe('Updated placeholder');
   });
 
-  it('handles paste events', () => {
+  it('inserts pasted text via execCommand so it can be undone', () => {
+    const testTabId = MynahUITabsStore.getInstance().addTab({
+      isSelected: true,
+      store: {}
+    }) as string;
+
+    let inputCalled = false;
+    const textInput = new PromptTextInput({
+      tabId: testTabId,
+      initMaxLength: 1000,
+      onKeydown: () => {},
+      onInput: () => { inputCalled = true; }
+    });
+
+    const inputElement = textInput.render.querySelector('.mynah-chat-prompt-input') as HTMLElement;
+
+    const originalExecCommand = document.execCommand;
+    const execCommandMock = jest.fn(() => true);
+    document.execCommand = execCommandMock as unknown as typeof document.execCommand;
+
+    const pasteEvent = new Event('paste', { bubbles: true, cancelable: true });
+    Object.defineProperty(pasteEvent, 'clipboardData', {
+      value: { getData: (type: string) => (type === 'text/plain' ? 'pasted text' : '') }
+    });
+    const preventDefaultSpy = jest.spyOn(pasteEvent, 'preventDefault');
+
+    inputElement.dispatchEvent(pasteEvent);
+
+    // The default paste is prevented and the text is inserted through
+    // execCommand('insertText'), which keeps it in the browser undo history.
+    expect(preventDefaultSpy).toHaveBeenCalled();
+    expect(execCommandMock).toHaveBeenCalledWith('insertText', false, 'pasted text');
+    expect(inputCalled).toBe(true);
+
+    document.execCommand = originalExecCommand;
+  });
+
+  it('falls back to manual insertion when execCommand is unavailable', () => {
     const testTabId = MynahUITabsStore.getInstance().addTab({
       isSelected: true,
       store: {}
@@ -125,9 +162,49 @@ describe('prompt-text-input', () => {
     });
 
     const inputElement = textInput.render.querySelector('.mynah-chat-prompt-input') as HTMLElement;
+    document.body.appendChild(textInput.render);
+
+    // Place a collapsed selection inside the input.
+    const range = document.createRange();
+    range.selectNodeContents(inputElement);
+    range.collapse(false);
+    const selection = window.getSelection();
+    selection?.removeAllRanges();
+    selection?.addRange(range);
+
+    const originalExecCommand = document.execCommand;
+    document.execCommand = jest.fn(() => false) as unknown as typeof document.execCommand;
+
+    const pasteEvent = new Event('paste', { bubbles: true, cancelable: true });
+    Object.defineProperty(pasteEvent, 'clipboardData', {
+      value: { getData: (type: string) => (type === 'text/plain' ? 'fallback text' : '') }
+    });
+
+    inputElement.dispatchEvent(pasteEvent);
+
+    expect(inputElement.textContent).toContain('fallback text');
+
+    document.execCommand = originalExecCommand;
+    document.body.removeChild(textInput.render);
+  });
+
+  it('ignores paste events without text content', () => {
+    const testTabId = MynahUITabsStore.getInstance().addTab({
+      isSelected: true,
+      store: {}
+    }) as string;
 
+    let inputCalled = false;
+    const textInput = new PromptTextInput({
+      tabId: testTabId,
+      initMaxLength: 1000,
+      onKeydown: () => {},
+      onInput: () => { inputCalled = true; }
+    });
+
+    const inputElement = textInput.render.querySelector('.mynah-chat-prompt-input') as HTMLElement;
     inputElement.dispatchEvent(new Event('paste'));
-    expect(textInput).toBeDefined();
+    expect(inputCalled).toBe(false);
   });
 
   it('manages text input value and clearing', () => {

src/components/chat-item/prompt-input/prompt-text-input.ts

@@ -133,18 +133,31 @@ export class PromptTextInput {
 
           // Get plain text from clipboard
           const text = e.clipboardData?.getData('text/plain');
-          if (text != null) {
-            // Insert text at cursor position
-            const selection = window.getSelection();
-            if ((selection?.rangeCount) != null) {
-              const range = selection.getRangeAt(0);
-              range.deleteContents();
-              range.insertNode(document.createTextNode(text));
-
-              // Move cursor to end of inserted text
-              range.collapse(false);
-              selection.removeAllRanges();
-              selection.addRange(range);
+          if (text != null && text !== '') {
+            // Insert via execCommand so the paste is recorded in the browser's
+            // native undo history. Manually inserting a text node (the fallback
+            // below) bypasses the undo stack, which breaks Ctrl/Cmd+Z after a paste.
+            let inserted = false;
+            try {
+              inserted = document.execCommand('insertText', false, text);
+            } catch {
+              inserted = false;
+            }
+
+            if (!inserted) {
+              // Fallback for environments where execCommand is unavailable:
+              // insert text at the cursor position manually.
+              const selection = window.getSelection();
+              if ((selection?.rangeCount) != null) {
+                const range = selection.getRangeAt(0);
+                range.deleteContents();
+                range.insertNode(document.createTextNode(text));
+
+                // Move cursor to end of inserted text
+                range.collapse(false);
+                selection.removeAllRanges();
+                selection.addRange(range);
+              }
             }
 
             // Check if input is empty and trigger input event

ui-tests/__test__/flows/quick-action-commands-header.ts

@@ -137,9 +137,9 @@ export const verifyQuickActionCommandsHeaderStatusVariations = async (page: Page
   let foundStatusClass = false;
 
   for (const statusClass of statusClasses) {
-    const hasStatus = await headerElement.evaluate((el, className) =>
+    const hasStatus = Boolean(await headerElement.evaluate((el, className) =>
       el.classList.contains(className), statusClass
-    );
+    ));
     if (hasStatus) {
       foundStatusClass = true;
       console.log(`Found status class: ${statusClass}`);