diff --git a/digital-avatar-app/backend/services/__init__.py b/digital-avatar-app/backend/services/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/digital-avatar-app/backend/services/boxim_client.py b/digital-avatar-app/backend/services/boxim_client.py
new file mode 100644
index 0000000..ce3071b
--- /dev/null
+++ b/digital-avatar-app/backend/services/boxim_client.py
@@ -0,0 +1,74 @@
+"""盒子 IM 客户端 — 封装网易云信 IM 接口调用"""
+import hashlib
+import random
+import string
+from datetime import datetime
+from typing import Optional
+
+import httpx
+
+
+class BoxIMClient:
+    """盒子 IM 客户端，通过会会平台网关调用网易云信 IM"""
+
+    def __init__(self, config: dict):
+        self.base_url = config.get("HUIHUI_IM_BASE_URL", "http://192.168.1.200:60040")
+        self.app_id = config.get("HUIHUI_APP_ID", "")
+        self.access_id = config.get("HUIHUI_ACCESS_ID", "")
+        self.access_secret = config.get("HUIHUI_ACCESS_SECRET", "")
+
+    def _build_sign_params(self, extra: dict) -> dict:
+        """构建带签名的请求参数（复用 news_service 签名模式）"""
+        nonce = "".join(random.choices(string.ascii_lowercase + string.digits, k=12))
+        timestamp = datetime.now().strftime("%Y%m%d%H%M%S")  # 24小时制
+        params = {
+            "appId": self.app_id,
+            "accessId": self.access_id,
+            "nonce": nonce,
+            "timestamp": timestamp,
+            **extra,
+        }
+        # 计算签名 — 排序 key, 过滤空值, 拼接后加 accessSecret, MD5 大写
+        keys = sorted(params.keys())
+        sign_parts = []
+        for k in keys:
+            v = params.get(k)
+            if v and v != "" and v != []:
+                sign_parts.append(f"{k}={v}")
+        sign_str = "&".join(sign_parts) + f"&accessSecret={self.access_secret}"
+        signature = hashlib.md5(sign_str.encode("utf-8")).hexdigest().upper()
+        params["signature"] = signature
+        params["signType"] = "MD5"
+        params["signVersion"] = "1.0"
+        return params
+
+    async def get_credentials(self, user_id: str) -> Optional[dict]:
+        """获取用户的网易云信 IM 凭证 (accid, token)"""
+        params = self._build_sign_params({"userId": user_id})
+        async with httpx.AsyncClient(timeout=10) as client:
+            r = await client.post(
+                f"{self.base_url}/box/netease",
+                params=params,
+            )
+        data = r.json()
+        if data.get("code") in (0, 200):
+            return data.get("data", {})
+        return None
+
+    async def send_p2p_message(
+        self, from_accid: str, to_accid: str, content: str
+    ) -> bool:
+        """发送单聊消息（文本）"""
+        params = self._build_sign_params({
+            "from": from_accid,
+            "to": to_accid,
+            "msgType": "text",
+            "content": content,
+        })
+        async with httpx.AsyncClient(timeout=10) as client:
+            r = await client.post(
+                f"{self.base_url}/box/message/send/p2p",
+                params=params,
+            )
+        data = r.json()
+        return data.get("code") in (0, 200)
diff --git a/digital-avatar-app/backend/tests/test_boxim_client.py b/digital-avatar-app/backend/tests/test_boxim_client.py
new file mode 100644
index 0000000..230bde2
--- /dev/null
+++ b/digital-avatar-app/backend/tests/test_boxim_client.py
@@ -0,0 +1,112 @@
+"""Tests for the Box IM client (Netease Yunxin gateway wrapper)."""
+import pytest
+from unittest.mock import AsyncMock, MagicMock, patch
+
+
+@pytest.fixture
+def mock_config():
+    return {
+        "HUIHUI_IM_BASE_URL": "http://192.168.1.200:60040",
+        "HUIHUI_APP_ID": "test_app",
+        "HUIHUI_ACCESS_ID": "test_access",
+        "HUIHUI_ACCESS_SECRET": "test_secret",
+    }
+
+
+def _make_mock_response(json_data: dict):
+    """Create a properly configured mock for httpx.Response."""
+    mock_response = MagicMock()
+    mock_response.json.return_value = json_data
+    return mock_response
+
+
+def _patch_httpx_client(json_data: dict):
+    """Patch httpx.AsyncClient so that `async with httpx.AsyncClient() as c: await c.post(...)` returns json_data."""
+    mock_client = AsyncMock()
+    mock_client.post.return_value = _make_mock_response(json_data)
+
+    mock_cm = AsyncMock()
+    mock_cm.__aenter__.return_value = mock_client
+    mock_cm.__aexit__.return_value = None
+
+    return patch("httpx.AsyncClient", return_value=mock_cm)
+
+
+@pytest.mark.asyncio
+async def test_get_credentials(mock_config):
+    """get_credentials should return accid and token from the gateway response."""
+    with _patch_httpx_client({"code": 200, "data": {"accid": "user123", "token": "tok_xyz"}}):
+        from services.boxim_client import BoxIMClient
+
+        client = BoxIMClient(mock_config)
+        result = await client.get_credentials("user123")
+
+        assert result["accid"] == "user123"
+        assert result["token"] == "tok_xyz"
+
+
+@pytest.mark.asyncio
+async def test_send_p2p_message_success(mock_config):
+    """send_p2p_message should return True when the gateway responds with code 200."""
+    with _patch_httpx_client({"code": 200}):
+        from services.boxim_client import BoxIMClient
+
+        client = BoxIMClient(mock_config)
+        result = await client.send_p2p_message("owner_acc", "target_acc", "Hello")
+
+        assert result is True
+
+
+@pytest.mark.asyncio
+async def test_send_p2p_message_failure(mock_config):
+    """send_p2p_message should return False when the gateway responds with a non-200 code."""
+    with _patch_httpx_client({"code": 500, "message": "error"}):
+        from services.boxim_client import BoxIMClient
+
+        client = BoxIMClient(mock_config)
+        result = await client.send_p2p_message("owner_acc", "target_acc", "Hello")
+
+        assert result is False
+
+
+@pytest.mark.asyncio
+async def test_get_credentials_returns_none_on_error(mock_config):
+    """get_credentials should return None when the gateway responds with an error code."""
+    with _patch_httpx_client({"code": 500, "message": "user not found"}):
+        from services.boxim_client import BoxIMClient
+
+        client = BoxIMClient(mock_config)
+        result = await client.get_credentials("nonexistent")
+
+        assert result is None
+
+
+def test_build_sign_params_contains_required_fields(mock_config):
+    """_build_sign_params should produce appId, accessId, nonce, timestamp, signature, signType, signVersion."""
+    from services.boxim_client import BoxIMClient
+
+    client = BoxIMClient(mock_config)
+    params = client._build_sign_params({"userId": "u1"})
+
+    assert "appId" in params
+    assert "accessId" in params
+    assert "nonce" in params
+    assert "timestamp" in params
+    assert "signature" in params
+    assert params["signType"] == "MD5"
+    assert params["signVersion"] == "1.0"
+    assert len(params["nonce"]) == 12
+
+
+def test_build_sign_params_signature_is_deterministic(mock_config):
+    """Same inputs should produce valid MD5 signatures."""
+    from services.boxim_client import BoxIMClient
+
+    client = BoxIMClient(mock_config)
+
+    params1 = client._build_sign_params({"userId": "u1"})
+    params2 = client._build_sign_params({"userId": "u1"})
+
+    assert params1["signature"] is not None
+    assert params2["signature"] is not None
+    assert len(params1["signature"]) == 32  # MD5 hex length