feat(dingtalk): prefix group replies with sender mention

In group chats, prefix the outbound markdown reply with an H1 naming the sender (# @<nick>) so the addressed user can spot it in a busy group. Private replies are sent verbatim.

Visual only: DingTalk markdown robot messages do not push real @ notifications (that would require staffId plumbing and a different message type). sender_name is read from OutboundMessage.metadata, which the agent loop already propagates from inbound metadata.

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

nanobot/channels/dingtalk/runtime.py

@@ -713,8 +713,15 @@ class DingTalkChannel(BaseChannel):
         if not token:
             raise RuntimeError("DingTalk access token unavailable")
 
-        if msg.content and msg.content.strip():
+        content = msg.content.strip() if msg.content else ""
-            if not await self._send_markdown_text(token, msg.chat_id, msg.content.strip()):
+        if content:
+            # In group chats, prefix the reply with a markdown header naming the
+            # sender so the addressed user can spot the reply. Visual only —
+            # DingTalk's markdown robot messages do not push real @ notifications.
+            sender_name = msg.metadata.get("sender_name") if msg.metadata else None
+            if msg.chat_id.startswith("group:") and sender_name:
+                content = f"# @{sender_name}\n\n{content}"
+            if not await self._send_markdown_text(token, msg.chat_id, content):
                 raise RuntimeError("DingTalk text message was not delivered")
 
         for media_ref in msg.media or []:

nanobot/channels/dingtalk/tests/test_dingtalk_channel.py

@@ -1,4 +1,5 @@
 import asyncio
+import json
 import zipfile
 from io import BytesIO
 from types import SimpleNamespace
@@ -252,6 +253,56 @@ async def test_group_send_uses_group_messages_api() -> None:
     assert call["json"]["msgKey"] == "sampleMarkdown"
 
 
+@pytest.mark.asyncio
+async def test_group_send_prepends_sender_mention(monkeypatch) -> None:
+    """Group replies are prefixed with a markdown header naming the sender."""
+    config = DingTalkConfig(client_id="app", client_secret="secret", allow_from=["*"])
+    channel = DingTalkChannel(config, MessageBus())
+    channel._http = _FakeHttp()
+
+    async def _fake_token() -> str:
+        return "token"
+
+    monkeypatch.setattr(channel, "_get_access_token", _fake_token)
+
+    await channel.send(
+        OutboundMessage(
+            channel="dingtalk",
+            chat_id="group:conv123",
+            content="hello",
+            metadata={"sender_name": "Alice"},
+        )
+    )
+
+    sent_text = json.loads(channel._http.calls[0]["json"]["msgParam"])["text"]
+    assert sent_text == "# @Alice\n\nhello"
+
+
+@pytest.mark.asyncio
+async def test_private_send_does_not_prepend_mention(monkeypatch) -> None:
+    """Private replies are sent verbatim, without the sender header."""
+    config = DingTalkConfig(client_id="app", client_secret="secret", allow_from=["*"])
+    channel = DingTalkChannel(config, MessageBus())
+    channel._http = _FakeHttp()
+
+    async def _fake_token() -> str:
+        return "token"
+
+    monkeypatch.setattr(channel, "_get_access_token", _fake_token)
+
+    await channel.send(
+        OutboundMessage(
+            channel="dingtalk",
+            chat_id="user1",  # private chat: no "group:" prefix
+            content="hello",
+            metadata={"sender_name": "Alice"},
+        )
+    )
+
+    sent_text = json.loads(channel._http.calls[0]["json"]["msgParam"])["text"]
+    assert sent_text == "hello"
+
+
 @pytest.mark.asyncio
 async def test_handler_uses_voice_recognition_text_when_text_is_empty(monkeypatch) -> None:
     bus = MessageBus()