fix: MCP DBCache 使用固定文件名 + 持久化缓存，重启秒恢复

- 缓存文件改用 md5(rel_key) 固定命名，放在 Temp/wechat_mcp_cache/
- mtime 映射持久化到 _mtimes.json，重启后验证一致直接复用
- 避免 mkstemp 随机文件名导致崩溃后临时文件堆积

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

mcp_server.py

@@ -120,10 +120,59 @@ def decrypt_wal(wal_path, out_path, enc_key):
 # ============ DB 缓存 ============
 
 class DBCache:
-    """缓存解密后的 DB，通过 mtime 检测变化"""
+    """缓存解密后的 DB，通过 mtime 检测变化。使用固定文件名，重启后可复用。"""
+
+    CACHE_DIR = os.path.join(tempfile.gettempdir(), "wechat_mcp_cache")
+    MTIME_FILE = os.path.join(tempfile.gettempdir(), "wechat_mcp_cache", "_mtimes.json")
 
     def __init__(self):
         self._cache = {}  # rel_key -> (db_mtime, wal_mtime, tmp_path)
+        os.makedirs(self.CACHE_DIR, exist_ok=True)
+        self._load_persistent_cache()
+
+    def _cache_path(self, rel_key):
+        """rel_key -> 固定的缓存文件路径"""
+        h = hashlib.md5(rel_key.encode()).hexdigest()[:12]
+        return os.path.join(self.CACHE_DIR, f"{h}.db")
+
+    def _load_persistent_cache(self):
+        """启动时从磁盘恢复缓存映射，验证 mtime 后复用"""
+        if not os.path.exists(self.MTIME_FILE):
+            return
+        try:
+            with open(self.MTIME_FILE) as f:
+                saved = json.load(f)
+        except (json.JSONDecodeError, OSError):
+            return
+        reused = 0
+        for rel_key, info in saved.items():
+            tmp_path = info["path"]
+            if not os.path.exists(tmp_path):
+                continue
+            rel_path = rel_key.replace('\\', os.sep)
+            db_path = os.path.join(DB_DIR, rel_path)
+            wal_path = db_path + "-wal"
+            try:
+                db_mtime = os.path.getmtime(db_path)
+                wal_mtime = os.path.getmtime(wal_path) if os.path.exists(wal_path) else 0
+            except OSError:
+                continue
+            if db_mtime == info["db_mt"] and wal_mtime == info["wal_mt"]:
+                self._cache[rel_key] = (db_mtime, wal_mtime, tmp_path)
+                reused += 1
+        if reused:
+            print(f"[DBCache] reused {reused} cached decrypted DBs from previous run", flush=True)
+
+    def _save_persistent_cache(self):
+        """持久化缓存映射到磁盘"""
+        data = {}
+        for rel_key, (db_mt, wal_mt, path) in self._cache.items():
+            data[rel_key] = {"db_mt": db_mt, "wal_mt": wal_mt, "path": path}
+        try:
+            with open(self.MTIME_FILE, 'w') as f:
+                json.dump(data, f)
+        except OSError:
+            pass
 
     def get(self, rel_key):
         if rel_key not in ALL_KEYS:
@@ -144,27 +193,19 @@ class DBCache:
             c_db_mt, c_wal_mt, c_path = self._cache[rel_key]
             if c_db_mt == db_mtime and c_wal_mt == wal_mtime and os.path.exists(c_path):
                 return c_path
-            try:
-                os.unlink(c_path)
-            except OSError:
-                pass
 
+        tmp_path = self._cache_path(rel_key)
         enc_key = bytes.fromhex(ALL_KEYS[rel_key]["enc_key"])
-        fd, tmp_path = tempfile.mkstemp(suffix='.db')
-        os.close(fd)
         full_decrypt(db_path, tmp_path, enc_key)
         if os.path.exists(wal_path):
             decrypt_wal(wal_path, tmp_path, enc_key)
         self._cache[rel_key] = (db_mtime, wal_mtime, tmp_path)
+        self._save_persistent_cache()
         return tmp_path
 
     def cleanup(self):
-        for _, _, path in self._cache.values():
-            try:
-                os.unlink(path)
-            except OSError:
-                pass
-        self._cache.clear()
+        """正常退出时保存缓存映射（不删文件，下次启动可复用）"""
+        self._save_persistent_cache()
 
 
 _cache = DBCache()