diff --git a/api/tests/unit_tests/services/enterprise/test_enterprise_service.py b/api/tests/unit_tests/services/enterprise/test_enterprise_service.py
new file mode 100644
index 0000000000..b4201aa061
--- /dev/null
+++ b/api/tests/unit_tests/services/enterprise/test_enterprise_service.py
@@ -0,0 +1,125 @@
+"""Unit tests for enterprise service integrations.
+
+This module covers the enterprise-only default workspace auto-join behavior:
+- Enterprise mode disabled: no external calls
+- Successful join / skipped join: no errors
+- Failures (network/invalid response/invalid UUID): soft-fail wrapper must not raise
+"""
+
+from unittest.mock import patch
+
+import pytest
+
+from services.enterprise.enterprise_service import (
+    DefaultWorkspaceJoinResult,
+    EnterpriseService,
+    try_join_default_workspace,
+)
+
+
+class TestJoinDefaultWorkspace:
+    def test_join_default_workspace_success(self):
+        account_id = "11111111-1111-1111-1111-111111111111"
+        response = {"workspace_id": "22222222-2222-2222-2222-222222222222", "joined": True, "message": "ok"}
+
+        with patch("services.enterprise.enterprise_service.EnterpriseRequest.send_request") as mock_send_request:
+            mock_send_request.return_value = response
+
+            result = EnterpriseService.join_default_workspace(account_id=account_id)
+
+            assert isinstance(result, DefaultWorkspaceJoinResult)
+            assert result.workspace_id == response["workspace_id"]
+            assert result.joined is True
+            assert result.message == "ok"
+
+            mock_send_request.assert_called_once_with(
+                "POST",
+                "/default-workspace/members",
+                json={"account_id": account_id},
+            )
+
+    def test_join_default_workspace_invalid_response_format_raises(self):
+        account_id = "11111111-1111-1111-1111-111111111111"
+
+        with patch("services.enterprise.enterprise_service.EnterpriseRequest.send_request") as mock_send_request:
+            mock_send_request.return_value = "not-a-dict"
+
+            with pytest.raises(ValueError, match="Invalid response format"):
+                EnterpriseService.join_default_workspace(account_id=account_id)
+
+    def test_join_default_workspace_invalid_account_id_raises(self):
+        with pytest.raises(ValueError):
+            EnterpriseService.join_default_workspace(account_id="not-a-uuid")
+
+
+class TestTryJoinDefaultWorkspace:
+    def test_try_join_default_workspace_enterprise_disabled_noop(self):
+        with (
+            patch("services.enterprise.enterprise_service.dify_config") as mock_config,
+            patch("services.enterprise.enterprise_service.EnterpriseService.join_default_workspace") as mock_join,
+        ):
+            mock_config.ENTERPRISE_ENABLED = False
+
+            try_join_default_workspace("11111111-1111-1111-1111-111111111111")
+
+            mock_join.assert_not_called()
+
+    def test_try_join_default_workspace_successful_join_does_not_raise(self):
+        account_id = "11111111-1111-1111-1111-111111111111"
+
+        with (
+            patch("services.enterprise.enterprise_service.dify_config") as mock_config,
+            patch("services.enterprise.enterprise_service.EnterpriseService.join_default_workspace") as mock_join,
+        ):
+            mock_config.ENTERPRISE_ENABLED = True
+            mock_join.return_value = DefaultWorkspaceJoinResult(
+                workspace_id="22222222-2222-2222-2222-222222222222",
+                joined=True,
+                message="ok",
+            )
+
+            # Should not raise
+            try_join_default_workspace(account_id)
+
+            mock_join.assert_called_once_with(account_id=account_id)
+
+    def test_try_join_default_workspace_skipped_join_does_not_raise(self):
+        account_id = "11111111-1111-1111-1111-111111111111"
+
+        with (
+            patch("services.enterprise.enterprise_service.dify_config") as mock_config,
+            patch("services.enterprise.enterprise_service.EnterpriseService.join_default_workspace") as mock_join,
+        ):
+            mock_config.ENTERPRISE_ENABLED = True
+            mock_join.return_value = DefaultWorkspaceJoinResult(
+                workspace_id="",
+                joined=False,
+                message="no default workspace configured",
+            )
+
+            # Should not raise
+            try_join_default_workspace(account_id)
+
+            mock_join.assert_called_once_with(account_id=account_id)
+
+    def test_try_join_default_workspace_api_failure_soft_fails(self):
+        account_id = "11111111-1111-1111-1111-111111111111"
+
+        with (
+            patch("services.enterprise.enterprise_service.dify_config") as mock_config,
+            patch("services.enterprise.enterprise_service.EnterpriseService.join_default_workspace") as mock_join,
+        ):
+            mock_config.ENTERPRISE_ENABLED = True
+            mock_join.side_effect = Exception("network failure")
+
+            # Should not raise
+            try_join_default_workspace(account_id)
+
+            mock_join.assert_called_once_with(account_id=account_id)
+
+    def test_try_join_default_workspace_invalid_account_id_soft_fails(self):
+        with patch("services.enterprise.enterprise_service.dify_config") as mock_config:
+            mock_config.ENTERPRISE_ENABLED = True
+
+            # Should not raise even though UUID parsing fails inside join_default_workspace
+            try_join_default_workspace("not-a-uuid")