diff --git a/workspace/frontend/components/issues/issue-mention-input.test.ts b/workspace/frontend/components/issues/issue-mention-input.test.ts
new file mode 100644
index 000000000..d24608ae1
--- /dev/null
+++ b/workspace/frontend/components/issues/issue-mention-input.test.ts
@@ -0,0 +1,36 @@
+// @vitest-environment jsdom
+import { act, createElement, useState } from 'react';
+import { createRoot } from 'react-dom/client';
+import { expect, it, vi } from 'vitest';
+import { IssueMentionInput } from './issue-mention-input';
+vi.mock('@/lib/i18n', () => ({ useT: () => (key: string) => key }));
+vi.mock('./issue-ui', () => ({ IssueAvatar: () => null }));
+it('replaces selected text with Markdown and preserves existing mention identities', async () => {
+  Object.assign(globalThis, { IS_REACT_ACT_ENVIRONMENT: true });
+  const host = document.createElement('div');
+  document.body.append(host);
+  const root = createRoot(host);
+  let saved = '';
+  function Editor() {
+    const [value, setValue] = useState('@alice@example.com replace');
+    saved = value;
+    return createElement(IssueMentionInput, { value, onValueChange: setValue,
+      mentions: [{ name: 'Alice', token: 'alice@example.com', source: 'human:alice@example.com', kind: 'human' }],
+    });
+  }
+  try {
+    await act(async () => root.render(createElement(Editor)));
+    const textarea = host.querySelector('textarea')!;
+    expect(textarea.value).toBe('@Alice replace');
+    textarea.setSelectionRange(7, 14);
+    const event = new Event('paste', { bubbles: true, cancelable: true });
+    Object.defineProperty(event, 'clipboardData', { value: { getData: (type: string) => type === 'text/html' ? '<strong>formatted</strong>' : '' } });
+    await act(async () => { textarea.dispatchEvent(event); });
+    expect(event.defaultPrevented).toBe(true);
+    expect(textarea.value).toBe('@Alice **formatted**');
+    expect(saved).toBe('@alice@example.com **formatted**');
+  } finally {
+    await act(async () => root.unmount());
+    host.remove();
+  }
+});
diff --git a/workspace/frontend/components/issues/issue-mention-input.tsx b/workspace/frontend/components/issues/issue-mention-input.tsx
index 7a3eb2d95..3c6e78b81 100644
--- a/workspace/frontend/components/issues/issue-mention-input.tsx
+++ b/workspace/frontend/components/issues/issue-mention-input.tsx
@@ -1,5 +1,6 @@
 'use client';
 import { useEffect, useId, useRef, useState, type ComponentProps } from 'react';
+import { clipboardMarkdown } from '@/lib/clipboard-markdown';
 import { Textarea } from '@/components/ui/textarea';
 import { useT } from '@/lib/i18n';
 import { cn } from '@/lib/utils';
@@ -26,6 +27,7 @@ export function IssueMentionInput({
   onKeyDown,
   onSelect,
   onBlur,
+  onPaste,
   ...props
 }: Props) {
   const t = useT();
@@ -86,6 +88,21 @@ export function IssueMentionInput({
         aria-activedescendant={
           open && items.length ? `${listId}-${active}` : undefined
         }
+        onPaste={(e) => {
+          onPaste?.(e);
+          if (e.defaultPrevented || props.disabled || props.readOnly) return;
+          const markdown = clipboardMarkdown(e.clipboardData);
+          if (markdown === null) return;
+          const { selectionStart: start, selectionEnd: end } = e.currentTarget;
+          const next = replaceMentionDraft(draft, start, end, markdown);
+          e.preventDefault();
+          if (props.maxLength !== undefined && next.length > props.maxLength) return;
+          onValueChange(next);
+          setRange(null);
+          requestAnimationFrame(() => {
+            input.current?.setSelectionRange(start + markdown.length, start + markdown.length);
+          });
+        }}
         onChange={(e) => {
           onValueChange(editMentionDraft(draft, e.target.value));
           detect(e.target);
diff --git a/workspace/frontend/lib/clipboard-markdown.test.ts b/workspace/frontend/lib/clipboard-markdown.test.ts
new file mode 100644
index 000000000..8419aa162
--- /dev/null
+++ b/workspace/frontend/lib/clipboard-markdown.test.ts
@@ -0,0 +1,24 @@
+// @vitest-environment jsdom
+import { expect, it } from 'vitest';
+import { clipboardMarkdown } from './clipboard-markdown';
+const clipboard = (html: string, markdown = '') => ({ getData: (type: string) => type === 'text/html' ? html : type === 'text/markdown' ? markdown : '' });
+it('preserves code blocks, bold, inline code and links from formatted text', () => {
+  const result = clipboardMarkdown(clipboard('<p>Login checker runs:</p><pre><code class="language-arduino">security find-generic-password -s "Claude Code-credentials" -w\n</code></pre><p>The <strong><code>-w</code> retrieves the stored secret itself</strong>. <a href="https://attack.mitre.org/techniques/T1555/001/">MITRE documents this technique</a>.</p>'));
+  expect(result).toContain('```arduino\nsecurity find-generic-password');
+  expect(result).toContain('**`-w` retrieves the stored secret itself**');
+  expect(result).toContain('[MITRE documents this technique](https://attack.mitre.org/techniques/T1555/001/)');
+});
+it('leaves plain-text Markdown to the native paste handler', () => {
+  expect(clipboardMarkdown(clipboard(''))).toBeNull();
+  expect(clipboardMarkdown(clipboard('<div>**bold** and `code`</div>'))).toBeNull();
+});
+it('prefers explicit Markdown over HTML', () => {
+  expect(clipboardMarkdown(clipboard('<strong>bold</strong>', '**original**'))).toBe('**original**');
+});
+it('preserves lists and headings while dropping active content and copy buttons', () => {
+  const result = clipboardMarkdown(clipboard('<h2>Steps</h2><ul><li>One</li><li><em>Two</em></li></ul><script>alert(1)</script><button>Copy code</button>'));
+  expect(result).toContain('## Steps');
+  expect(result).toMatch(/-\s+One/);
+  expect(result).toContain('_Two_');
+  expect(result).not.toMatch(/alert|Copy code/);
+});
diff --git a/workspace/frontend/lib/clipboard-markdown.ts b/workspace/frontend/lib/clipboard-markdown.ts
new file mode 100644
index 000000000..7fccbc667
--- /dev/null
+++ b/workspace/frontend/lib/clipboard-markdown.ts
@@ -0,0 +1,26 @@
+import TurndownService from 'turndown';
+
+/** Return Markdown for rich clipboard content, or null for native plain-text paste. */
+export function clipboardMarkdown(clipboard: Pick<DataTransfer, 'getData'>): string | null {
+  const markdown = clipboard.getData('text/markdown');
+  if (markdown) return markdown;
+  const html = clipboard.getData('text/html');
+  if (!html) return null;
+  try {
+    // Parse in an inert document; never mount clipboard HTML in the page.
+    const document = new DOMParser().parseFromString(html, 'text/html');
+    document.querySelectorAll('script, style, iframe, object, button, input, select, textarea').forEach(node => node.remove());
+    // Plain text copied from editors is often wrapped in a div or span. Keep it
+    // verbatim rather than escaping Markdown syntax that the user already wrote.
+    if (!document.body.querySelector('strong, b, em, i, s, del, a, pre, code, h1, h2, h3, h4, h5, h6, ul, ol, blockquote, hr, img')) return null;
+    const converter = new TurndownService({ headingStyle: 'atx', codeBlockStyle: 'fenced', bulletListMarker: '-' });
+    converter.addRule('strikethrough', {
+      filter: ['s', 'del'],
+      replacement: content => `~~${content}~~`,
+    });
+    const result = converter.turndown(document.body);
+    return result.trim() ? result : null;
+  } catch {
+    return null; // Clipboard formats vary; ordinary paste must still work.
+  }
+}
diff --git a/workspace/frontend/package-lock.json b/workspace/frontend/package-lock.json
index 7b7ca0fc6..4e1c40dcc 100644
--- a/workspace/frontend/package-lock.json
+++ b/workspace/frontend/package-lock.json
@@ -30,6 +30,7 @@
         "remark-gfm": "^4.0.1",
         "sonner": "^2.0.7",
         "tailwind-merge": "^3.4.0",
+        "turndown": "^7.2.4",
         "tw-animate-css": "^1.4.0",
         "vaul": "^1.1.2"
       },
@@ -41,6 +42,7 @@
         "@types/node": "^24.3.0",
         "@types/react": "^19.2.7",
         "@types/react-dom": "^19.2.3",
+        "@types/turndown": "^5.0.6",
         "@vitejs/plugin-react": "^5.2.0",
         "jsdom": "^29.1.1",
         "postcss": "^8.5.6",
@@ -2481,6 +2483,12 @@
         "@chevrotain/types": "~11.1.1"
       }
     },
+    "node_modules/@mixmark-io/domino": {
+      "version": "2.2.0",
+      "resolved": "https://registry.npmjs.org/@mixmark-io/domino/-/domino-2.2.0.tgz",
+      "integrity": "sha512-Y28PR25bHXUg88kCV7nivXrP2Nj2RueZ3/l/jdx6J9f8J4nsEGcgX0Qe6lt7Pa+J79+kPiJU3LguR6O/6zrLOw==",
+      "license": "BSD-2-Clause"
+    },
     "node_modules/@napi-rs/lzma-linux-x64-gnu": {
       "version": "1.5.1",
       "resolved": "https://registry.npmjs.org/@napi-rs/lzma-linux-x64-gnu/-/lzma-linux-x64-gnu-1.5.1.tgz",
@@ -5843,6 +5851,13 @@
       "license": "MIT",
       "optional": true
     },
+    "node_modules/@types/turndown": {
+      "version": "5.0.6",
+      "resolved": "https://registry.npmjs.org/@types/turndown/-/turndown-5.0.6.tgz",
+      "integrity": "sha512-ru00MoyeeouE5BX4gRL+6m/BsDfbRayOskWqUvh7CLGW+UXxHQItqALa38kKnOiZPqJrtzJUgAC2+F0rL1S4Pg==",
+      "dev": true,
+      "license": "MIT"
+    },
     "node_modules/@types/unist": {
       "version": "3.0.3",
       "resolved": "https://registry.npmjs.org/@types/unist/-/unist-3.0.3.tgz",
@@ -10225,6 +10240,19 @@
       "integrity": "sha512-oJFu94HQb+KVduSUQL7wnpmqnfmLsOA/nAh6b6EH0wCEoK0/mPeXU6c3wKDV83MkOuHPRHtSXKKU99IBazS/2w==",
       "license": "0BSD"
     },
+    "node_modules/turndown": {
+      "version": "7.2.4",
+      "resolved": "https://registry.npmjs.org/turndown/-/turndown-7.2.4.tgz",
+      "integrity": "sha512-I8yFsfRzmzK0WV1pNNOA4A7y4RDfFxPRxb3t+e3ui14qSGOxGtiSP6GjeX+Y6CHb7HYaFj7ECUD7VE5kQMZWGQ==",
+      "license": "MIT",
+      "dependencies": {
+        "@mixmark-io/domino": "^2.2.0"
+      },
+      "engines": {
+        "node": ">=18",
+        "npm": ">=9"
+      }
+    },
     "node_modules/tw-animate-css": {
       "version": "1.4.0",
       "resolved": "https://registry.npmjs.org/tw-animate-css/-/tw-animate-css-1.4.0.tgz",
diff --git a/workspace/frontend/package.json b/workspace/frontend/package.json
index 51c7cc4d4..c36a18d72 100644
--- a/workspace/frontend/package.json
+++ b/workspace/frontend/package.json
@@ -34,6 +34,7 @@
     "remark-gfm": "^4.0.1",
     "sonner": "^2.0.7",
     "tailwind-merge": "^3.4.0",
+    "turndown": "^7.2.4",
     "tw-animate-css": "^1.4.0",
     "vaul": "^1.1.2"
   },
@@ -45,6 +46,7 @@
     "@types/node": "^24.3.0",
     "@types/react": "^19.2.7",
     "@types/react-dom": "^19.2.3",
+    "@types/turndown": "^5.0.6",
     "@vitejs/plugin-react": "^5.2.0",
     "jsdom": "^29.1.1",
     "postcss": "^8.5.6",