diff --git a/src/blackboard/db.py b/src/blackboard/db.py
index 934866c..8a2ab8a 100644
--- a/src/blackboard/db.py
+++ b/src/blackboard/db.py
@@ -36,6 +36,78 @@ def _migrate_v261(conn: sqlite3.Connection) -> None:
         pass
 
 
+def _migrate_v27(conn: sqlite3.Connection) -> None:
+    """v2.7 数据迁移：cards 表 + 所有表加 card_id/stage"""
+    # 1. cards 表（CREATE IF NOT EXISTS 已处理）
+    for stmt in _CARDS_SCHEMA:
+        try:
+            conn.execute(stmt)
+        except sqlite3.OperationalError:
+            pass
+
+    # 2. 所有表加 card_id
+    for table in ("tasks", "outputs", "reviews", "comments", "events",
+                  "task_attempts", "routing_decisions"):
+        _safe_add_column(conn, table, "card_id", "TEXT")
+
+    # 3. tasks 加 stage
+    _safe_add_column(conn, "tasks", "stage", "TEXT")
+
+    # 4. card_id 索引
+    for table in ("tasks", "events"):
+        try:
+            conn.execute(
+                f"CREATE INDEX IF NOT EXISTS idx_{table}_card ON {table}(card_id)")
+        except sqlite3.OperationalError:
+            pass
+
+    # 5. 回填 card_id = 'default'（分批，避免大表锁太久）
+    for table in ("tasks", "outputs", "reviews", "comments", "events",
+                  "task_attempts", "routing_decisions"):
+        try:
+            row = conn.execute(
+                f"SELECT COUNT(*) as cnt FROM {table} WHERE card_id IS NULL"
+            ).fetchone()
+            if row and row["cnt"] > 0:
+                # 分批更新，每批 500 行
+                _batch_update_card_id(conn, table, "default", batch_size=500)
+        except sqlite3.OperationalError:
+            pass  # 表不存在则跳过
+
+    # 6. 创建 default Card（如果不存在）
+    try:
+        existing = conn.execute(
+            "SELECT id FROM cards WHERE id='default'"
+        ).fetchone()
+        if not existing:
+            conn.execute(
+                "INSERT INTO cards (id, name, status, card_type, stages_json, labels_json, created_at) "
+                "VALUES ('default', 'Default', 'active', 'default', '[]', '[]', datetime('now'))"
+            )
+    except sqlite3.OperationalError:
+        pass  # cards 表不存在则跳过（不应该发生）
+
+
+def _batch_update_card_id(conn: sqlite3.Connection, table: str,
+                           card_id: str, batch_size: int = 500) -> None:
+    """分批更新 card_id，避免大表长时间锁"""
+    while True:
+        conn.execute(
+            f"UPDATE {table} SET card_id=? WHERE rowid IN ("
+            f"SELECT rowid FROM {table} WHERE card_id IS NULL LIMIT {batch_size})",
+            (card_id,),
+        )
+        if conn.total_changes == 0:
+            break
+        conn.commit()
+        # 检查是否还有剩余
+        row = conn.execute(
+            f"SELECT COUNT(*) as cnt FROM {table} WHERE card_id IS NULL"
+        ).fetchone()
+        if not row or row["cnt"] == 0:
+            break
+
+
 def _safe_add_column(conn: sqlite3.Connection, table: str,
                      column: str, col_type: str) -> None:
     """安全添加列（已存在则跳过）"""