diff --git a/src/blackboard/db.py b/src/blackboard/db.py
index 2d9edd6..e1b9ab3 100644
--- a/src/blackboard/db.py
+++ b/src/blackboard/db.py
@@ -48,7 +48,7 @@ def _migrate_v27(conn: sqlite3.Connection) -> None:
 
 
 def _migrate_v28(conn: sqlite3.Connection) -> None:
-    """v2.8 数据迁移：3 新状态 + 归档字段 + CHECK 约束更新"""
+    """v2.8 数据迁移：3 新状态 + 归档字段 + CHECK 约束更新 + checkpoints 表"""
     # 1. 添加归档字段
     _safe_add_column(conn, "tasks", "archived", "INTEGER DEFAULT 0")
     _safe_add_column(conn, "tasks", "archived_at", "TEXT")
@@ -104,6 +104,29 @@ def _migrate_v28(conn: sqlite3.Connection) -> None:
             CREATE INDEX IF NOT EXISTS idx_tasks_current_agent ON tasks(current_agent);
         """)
 
+    # 3. checkpoints 表（M3）
+    conn.execute("""CREATE TABLE IF NOT EXISTS checkpoints (
+        id TEXT PRIMARY KEY,
+        task_id TEXT NOT NULL REFERENCES tasks(id),
+        type TEXT NOT NULL CHECK (type IN ('verify', 'decision', 'action')),
+        title TEXT NOT NULL,
+        description TEXT,
+        status TEXT NOT NULL DEFAULT 'pending' CHECK (status IN ('pending', 'approved', 'rejected')),
+        payload TEXT NOT NULL,
+        created_at TEXT NOT NULL DEFAULT (datetime('now')),
+        resolved_at TEXT,
+        resolved_by TEXT,
+        resolve_note TEXT
+    )""")
+    conn.execute("CREATE INDEX IF NOT EXISTS idx_checkpoints_task ON checkpoints(task_id)")
+    conn.execute("CREATE INDEX IF NOT EXISTS idx_checkpoints_status ON checkpoints(status)")
+
+    # 4. outputs 扩展字段（M3 成果物）
+    _safe_add_column(conn, "outputs", "file_name", "TEXT")
+    _safe_add_column(conn, "outputs", "file_size", "INTEGER")
+    _safe_add_column(conn, "outputs", "file_path", "TEXT")
+    _safe_add_column(conn, "outputs", "mime_type", "TEXT")
+
 
 def _safe_add_column(conn: sqlite3.Connection, table: str,
                      column: str, col_type: str) -> None: