diff --git a/src/api/server.ts b/src/api/server.ts
index 45dbc95..58bb210 100644
--- a/src/api/server.ts
+++ b/src/api/server.ts
@@ -25,6 +25,70 @@ function dataDir(): string {
   return process.env.MAESTRO_DATA_DIR ?? join(homedir(), '.maestro');
 }
 
+/** 常见 MIME → 落盘扩展名（无前导点）。剪贴板粘贴 blob 常无扩展名，据此补齐。 */
+const MIME_EXT: Record<string, string> = {
+  'image/png': 'png',
+  'image/jpeg': 'jpg',
+  'image/jpg': 'jpg',
+  'image/gif': 'gif',
+  'image/webp': 'webp',
+  'image/svg+xml': 'svg',
+  'image/bmp': 'bmp',
+  'image/x-icon': 'ico',
+  'image/vnd.microsoft.icon': 'ico',
+  'image/tiff': 'tiff',
+  'image/heic': 'heic',
+  'image/heif': 'heif',
+  'image/avif': 'avif',
+  'application/pdf': 'pdf',
+  'application/zip': 'zip',
+  'application/json': 'json',
+  'application/xml': 'xml',
+  'text/plain': 'txt',
+  'text/markdown': 'md',
+  'text/csv': 'csv',
+  'text/html': 'html',
+};
+
+/** MIME 类型 → 扩展名（无点）。未知映射时对 image/<subtype> 兜底取 subtype；其余返回 ''。 */
+export function extFromMime(mimetype: string | undefined): string {
+  if (!mimetype) return '';
+  const key = mimetype.split(';')[0].trim().toLowerCase();
+  if (MIME_EXT[key]) return MIME_EXT[key];
+  const m = key.match(/^image\/([a-z0-9.+-]+)$/);
+  if (m) return m[1].replace(/[^a-z0-9]/g, '');
+  return '';
+}
+
+/** basename 末尾是否带「看起来像扩展名」的后缀（1-8 位字母数字）。 */
+function hasExtension(name: string): boolean {
+  return /\.[A-Za-z0-9]{1,8}$/.test(name);
+}
+
+/**
+ * 计算附件落盘安全文件名。规则：
+ * 1. 仅取 basename，净化非法字符（`[^\w.\-]` → `_`），剥掉前导点（防隐藏/空名）。
+ * 2. 主名为空或为占位名（blob/image/file/unknown/untitled/paste）→ 视为「无名粘贴 blob」，
+ *    生成唯一名 `paste-<ts>-<seq>`，扩展名优先取 mimetype 推断、其次保留原扩展名。
+ * 3. 有正常主名但缺扩展名 → 按 mimetype 补扩展名（mimetype 未知则保持原样）。
+ * 返回值保证非空。
+ */
+export function safeAttachmentName(rawName: string | undefined, mimetype: string | undefined, seq = 0): string {
+  const ext = extFromMime(mimetype);
+  const sanitized = basename((rawName ?? '').trim()).replace(/[^\w.\-]/g, '_').replace(/^\.+/, '');
+  const withExt = hasExtension(sanitized);
+  const stem = withExt ? sanitized.replace(/\.[A-Za-z0-9]{1,8}$/, '') : sanitized;
+  const isPlaceholder = stem === '' || /^(blob|image|file|unknown|untitled|paste)$/i.test(stem);
+  if (isPlaceholder) {
+    const origExt = withExt ? sanitized.slice(sanitized.lastIndexOf('.') + 1) : '';
+    const useExt = ext || origExt;
+    const base = `paste-${Date.now()}-${seq}`;
+    return useExt ? `${base}.${useExt}` : base;
+  }
+  if (!withExt && ext) return `${sanitized}.${ext}`;
+  return sanitized;
+}
+
 /** Project 出参：附加 hasTodoJson（<repoPath>/todo/todo.json 是否存在，每次序列化时算） */
 function projectOut(p: Project, store: Store): Project & { hasTodoJson: boolean; summary: ReturnType<Store['projectSummary']> } {
   return { ...p, hasTodoJson: hasTodoJson(p.repoPath), summary: store.projectSummary(p.id) };
@@ -280,11 +344,13 @@ export function buildServer(opts: ApiOptions): FastifyInstance {
     const dir = join(dataDir(), 'tasks', id, 'attachments');
     mkdirSync(dir, { recursive: true });
     const saved: Array<{ name: string; type: string; path: string }> = [];
+    let seq = 0;
     for await (const part of req.files()) {
-      const safe = basename(part.filename).replace(/[^\w.\-]/g, '_') || `file-${Date.now()}`;
+      // 无名/无扩展名（如剪贴板粘贴 blob）→ 按 mimetype 生成安全文件名+扩展名
+      const safe = safeAttachmentName(part.filename, part.mimetype, seq++);
       await pipeline(part.file, createWriteStream(join(dir, safe)));
-      if (part.file.truncated) return reply.code(400).send({ error: `文件 ${part.filename} 超过 25MB 上限` });
-      saved.push({ name: part.filename, type: part.mimetype, path: `tasks/${id}/attachments/${safe}` });
+      if (part.file.truncated) return reply.code(400).send({ error: `文件 ${part.filename || safe} 超过 25MB 上限` });
+      saved.push({ name: part.filename || safe, type: part.mimetype, path: `tasks/${id}/attachments/${safe}` });
     }
     if (saved.length === 0) return reply.code(400).send({ error: '未收到文件' });
     return { attachments: store.addAttachments(id, saved) };