diff --git a/backend/packages/harness/deerflow/client.py b/backend/packages/harness/deerflow/client.py
index ece067c452..0203dc965d 100644
--- a/backend/packages/harness/deerflow/client.py
+++ b/backend/packages/harness/deerflow/client.py
@@ -254,7 +254,7 @@ class DeerFlowClient:
         self._checkpoint_channel_mode = freeze_checkpoint_channel_mode(self._app_config.database.checkpoint_channel_mode)
         self._checkpoint_snapshot_frequency = freeze_checkpoint_snapshot_frequency(self._app_config.database.checkpoint_delta.snapshot_frequency)
 
-        if agent_name is not None and not AGENT_NAME_PATTERN.match(agent_name):
+        if agent_name is not None and not AGENT_NAME_PATTERN.fullmatch(agent_name):
             raise ValueError(f"Invalid agent name '{agent_name}'. Must match pattern: {AGENT_NAME_PATTERN.pattern}")
 
         self._checkpointer = checkpointer
diff --git a/backend/tests/test_client.py b/backend/tests/test_client.py
index b49167c9d6..daccabdbf2 100644
--- a/backend/tests/test_client.py
+++ b/backend/tests/test_client.py
@@ -121,6 +121,13 @@ class TestClientInit:
             with pytest.raises(ValueError, match="Invalid agent name"):
                 DeerFlowClient(agent_name="../path/traversal")
 
+    def test_agent_name_with_trailing_newline_rejected(self, mock_app_config):
+        with patch("deerflow.client.get_app_config", return_value=mock_app_config):
+            # The client's own guard must reject this at construction; the
+            # memory store's later fullmatch check uses different phrasing.
+            with pytest.raises(ValueError, match="Must match pattern"):
+                DeerFlowClient(agent_name="reviewer\n")
+
     def test_custom_config_path(self, mock_app_config):
         with (
             patch("deerflow.client.reload_app_config") as mock_reload,