diff --git a/__pycache__/config.cpython-312.pyc b/__pycache__/config.cpython-312.pyc
index 272594c..f416cb9 100644
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diff --git a/__pycache__/crypto_utils.cpython-312.pyc b/__pycache__/crypto_utils.cpython-312.pyc
index aa20361..a9b545f 100644
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diff --git a/__pycache__/main.cpython-312.pyc b/__pycache__/main.cpython-312.pyc
index 9f5730c..83a2cdb 100644
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diff --git a/crypto_utils.py b/crypto_utils.py
index 096b69c..025568c 100644
--- a/crypto_utils.py
+++ b/crypto_utils.py
@@ -43,24 +43,36 @@ def aes_decrypt_base64(cipher_b64: str, encoding_aes_key: str) -> str:
     cipher = AES.new(aes_key, AES.MODE_CBC, iv)
     decrypted = cipher.decrypt(cipher_bytes)
     decrypted = pkcs5_unpadding(decrypted)
-    # 微信消息体格式：16B随机串 + 4B网络序长度 + 明文 + appid
-    if len(decrypted) < 20:
-        raise ValueError("解密后消息长度非法")
-    content = decrypted[16:]
-    msg_len = struct.unpack("!I", content[:4])[0]
-    msg_start = 4
-    msg_end = msg_start + msg_len
-    if msg_end > len(content):
-        raise ValueError("解密后消息长度字段越界")
-    msg = content[msg_start:msg_end]
-    return msg.decode("utf-8")
+    # 兼容两种格式：
+    # 1) 微信消息体：16B随机串 + 4B长度 + 明文 + appid
+    # 2) 纯文本：直接是明文 JSON/XML
+    try:
+        if len(decrypted) < 20:
+            raise ValueError("payload too short")
+        content = decrypted[16:]
+        msg_len = struct.unpack("!I", content[:4])[0]
+        msg_start = 4
+        msg_end = msg_start + msg_len
+        if msg_end > len(content):
+            raise ValueError("msg length out of range")
+        msg = content[msg_start:msg_end]
+        text = msg.decode("utf-8")
+        if text:
+            return text
+    except Exception:
+        pass
+    return decrypted.decode("utf-8")
 
 
-def aes_encrypt_base64(plaintext: str, encoding_aes_key: str, app_id: str) -> str:
+def aes_encrypt_base64(plaintext: str, encoding_aes_key: str, app_id: str | None = None) -> str:
     aes_key, iv = get_aes_key_and_iv(encoding_aes_key)
     raw = plaintext.encode("utf-8")
-    # 微信消息体格式：16B随机串 + 4B网络序长度 + 明文 + appid
-    data = os.urandom(16) + struct.pack("!I", len(raw)) + raw + app_id.encode("utf-8")
+    if app_id:
+        # 微信消息体格式：16B随机串 + 4B网络序长度 + 明文 + appid
+        data = os.urandom(16) + struct.pack("!I", len(raw)) + raw + app_id.encode("utf-8")
+    else:
+        # 纯明文格式
+        data = raw
     padded = pkcs5_padding(data)
     cipher = AES.new(aes_key, AES.MODE_CBC, iv)
     encrypted = cipher.encrypt(padded)
diff --git a/main.py b/main.py
index c8f1321..8d11934 100644
--- a/main.py
+++ b/main.py
@@ -597,10 +597,15 @@ async def _handle_wechat_request(request: Request, app_id: Optional[str], backgr
     logger.info("回包明文（加密前）: %s", resp_json_str)
 
     # 8. 加密响应
-    # XML 回调场景使用当前会话 appid（公众号 appid）加密，避免与开放 API appid 不一致导致平台解密失败。
-    response_app_id = APP_ID
+    # - /?app_id=... 的第三方服务接口请求通常使用纯AES明文加密（不拼接 appid）
+    # - XML 回调场景使用会话 appid 封装加密
+    # - 其余 JSON 场景默认使用纯AES，提升兼容性
+    response_app_id: Optional[str] = None
     if str(data.get("_payload_format", "")) == "xml":
         response_app_id = str(data.get("ChannelId", "") or data.get("appid", "")).strip() or APP_ID
+    elif app_id:
+        response_app_id = None
+    logger.info("响应加密模式: %s", "envelope" if response_app_id else "plain")
     try:
         encrypted_resp = aes_encrypt_base64(resp_json_str, ENCODING_AES_KEY, response_app_id)
     except Exception as e: