diff --git a/plugins/platforms/teams/adapter.py b/plugins/platforms/teams/adapter.py
index 2729de8f41..cdec7e3f1e 100644
--- a/plugins/platforms/teams/adapter.py
+++ b/plugins/platforms/teams/adapter.py
@@ -512,7 +512,14 @@ class TeamsAdapter(BasePlatformAdapter):
                 if reply_to and reply_to.isdigit() and reply_to != "0":
                     try:
                         result = await self._app.reply(chat_id, reply_to, chunk)
-                    except Exception:
+                    except Exception as reply_err:
+                        # Group chats 400 on threaded sends; the Teams SDK
+                        # doesn't expose typed HTTP errors, so fall back on
+                        # any exception and log for diagnostics.
+                        logger.debug(
+                            "Teams reply() failed, falling back to flat send: %s",
+                            reply_err,
+                        )
                         result = await self._app.send(chat_id, chunk)
                 else:
                     result = await self._app.send(chat_id, chunk)
diff --git a/website/docs/user-guide/messaging/index.md b/website/docs/user-guide/messaging/index.md
index c68bdae91c..25e8e4598f 100644
--- a/website/docs/user-guide/messaging/index.md
+++ b/website/docs/user-guide/messaging/index.md
@@ -60,9 +60,9 @@ flowchart TB
     bb[BlueBubbles]
     qq[QQ]
     yb[Yuanbao]
-            ms[Microsoft Teams]
-            api["API Server<br/>(OpenAI-compatible)"]
-            wh[Webhooks]
+    ms[Microsoft Teams]
+    api["API Server<br/>(OpenAI-compatible)"]
+    wh[Webhooks]
         end
 
         store["Session store<br/>per chat"]