diff --git a/apps/web/src/components/ChatComposer.tsx b/apps/web/src/components/ChatComposer.tsx
index d63300c89..4607e3a7a 100644
--- a/apps/web/src/components/ChatComposer.tsx
+++ b/apps/web/src/components/ChatComposer.tsx
@@ -1962,6 +1962,37 @@ export const ChatComposer = forwardRef<ChatComposerHandle, Props>(
               }}
             />
             <div className="composer-tools-wrap">
+              <button
+                type="button"
+                className="icon-btn"
+                onClick={() => {
+                  const ta = textareaRef.current;
+                  if (!ta) return;
+                  const cursor = ta.selectionStart;
+                  const before = draft.slice(0, cursor);
+                  const after = draft.slice(cursor);
+                  const next = before + '@' + after;
+                  setDraft(next);
+                  // Manually open the mention popover, same as handleChange
+                  // does when it detects a fresh @ in the typed input.
+                  const pos = cursor + 1;
+                  const textBefore = next.slice(0, pos);
+                  const m = /(^|\\s)@([^\\s@]*)$/.exec(textBefore);
+                  if (m) {
+                    setMention({ q: m[2] ?? '', cursor: pos });
+                  } else {
+                    setMention(null);
+                  }
+                  requestAnimationFrame(() => {
+                    ta.focus();
+                    ta.setSelectionRange(pos, pos);
+                  });
+                }}
+                title={t('chat.mentionButtonTitle')}
+                aria-label={t('chat.mentionButtonAria')}
+              >
+                <span style={{ fontFamily: 'monospace', fontSize: 15 }}>@</span>
+              </button>
               <button
                 ref={toolsTriggerRef}
                 type="button"
diff --git a/apps/web/src/i18n/locales/en.ts b/apps/web/src/i18n/locales/en.ts
index f2cd3cd78..91e67fc0e 100644
--- a/apps/web/src/i18n/locales/en.ts
+++ b/apps/web/src/i18n/locales/en.ts
@@ -1517,6 +1517,8 @@ export const en: Dict = {
   'chat.send': 'Send',
   'chat.stop': 'Stop',
   'chat.removeAria': 'Remove {name}',
+  'chat.mentionButtonTitle': 'Mention a file',
+  'chat.mentionButtonAria': 'Open file mention picker',
   'chat.example1Title': 'Editorial pitch deck',
   'chat.example1Tag': 'Magazine',
   'chat.example1Prompt':
diff --git a/apps/web/src/i18n/locales/zh-CN.ts b/apps/web/src/i18n/locales/zh-CN.ts
index 115f85b82..703ddf604 100644
--- a/apps/web/src/i18n/locales/zh-CN.ts
+++ b/apps/web/src/i18n/locales/zh-CN.ts
@@ -1508,6 +1508,8 @@ export const zhCN: Dict = {
   'chat.send': '发送',
   'chat.stop': '停止',
   'chat.removeAria': '移除 {name}',
+  'chat.mentionButtonTitle': '引用文件',
+  'chat.mentionButtonAria': '打开文件引用选择器',
   'chat.example1Title': '编辑风路演 PPT',
   'chat.example1Tag': '杂志',
   'chat.example1Prompt':
diff --git a/apps/web/src/i18n/types.ts b/apps/web/src/i18n/types.ts
index 967c33ef3..b7c9ad925 100644
--- a/apps/web/src/i18n/types.ts
+++ b/apps/web/src/i18n/types.ts
@@ -1842,6 +1842,8 @@ export interface Dict {
   'chat.send': string;
   'chat.stop': string;
   'chat.removeAria': string;
+  'chat.mentionButtonTitle': string;
+  'chat.mentionButtonAria': string;
   'chat.example1Title': string;
   'chat.example1Tag': string;
   'chat.example1Prompt': string;