Fix combinator serialization issue (#3726)

* Fix combinator serialization issue

* CI

Author: vincent0426

ee/vellum_ee/workflows/display/nodes/vellum/conditional_node.py

@@ -188,6 +188,7 @@ def serialize_rule(
                 rule_ids = self._get_rule_ids()
                 condition_rule = serialize_rule(port._condition, [idx], rule_ids[idx] if len(rule_ids) > idx else None)
                 rules = condition_rule["rules"] if condition_rule["rules"] else [condition_rule]
+                combinator = condition_rule.get("combinator") or "AND"
                 if port._condition_type is None:
                     raise ValueError("Condition type is None, but a valid ConditionType is expected.")
                 conditions.append(
@@ -198,7 +199,7 @@ def serialize_rule(
                         "data": {
                             "id": rule_group_id,
                             "rules": rules,
-                            "combinator": "AND",
+                            "combinator": combinator,
                             "negated": False,
                             "field_node_input_id": None,
                             "operator": None,

ee/vellum_ee/workflows/display/tests/workflow_serialization/test_basic_conditional_node_serialization.py

@@ -1,4 +1,5 @@
 import pytest
+from typing import Any, cast
 
 from deepdiff import DeepDiff
 
@@ -23,7 +24,10 @@
 from vellum_ee.workflows.display.workflows.get_vellum_workflow_display_class import get_workflow_display
 
 from tests.workflows.basic_conditional_node.workflow import CategoryWorkflow
-from tests.workflows.basic_conditional_node.workflow_with_only_one_conditional_node import create_simple_workflow
+from tests.workflows.basic_conditional_node.workflow_with_only_one_conditional_node import (
+    Inputs as SimpleInputs,
+    create_simple_workflow,
+)
 
 
 def test_serialize_workflow():
@@ -924,3 +928,26 @@ def test_conditional_node_serialize_all_operators_with_value_and_start_and_end(d
         conditional_node,
         ignore_order=True,
     )
+
+
+def test_conditional_node_serialize_or_combinator_preserves_or():
+    """Regression test: OR conditions (A | B) must serialize with combinator 'OR', not 'AND'."""
+    # GIVEN a conditional node with an OR condition: text == "foo" OR text == "bar"
+    or_condition = SimpleInputs.text.equals("foo") | SimpleInputs.text.equals("bar")
+    workflow_cls = create_simple_workflow(or_condition)
+
+    workflow_display = get_workflow_display(workflow_class=workflow_cls)
+    serialized_workflow = cast(dict[str, Any], workflow_display.serialize())
+
+    # WHEN we extract the conditional node's IF condition
+    conditional_node = next(
+        n
+        for n in serialized_workflow["workflow_raw_data"]["nodes"]
+        if (n.get("base") or {}).get("name") == "ConditionalNode"
+    )
+    if_condition = next(c for c in conditional_node["data"]["conditions"] if c["type"] == "IF")
+
+    # THEN the combinator must be "OR" (not "AND")
+    assert (
+        if_condition["data"]["combinator"] == "OR"
+    ), "OR conditions were incorrectly serialized as AND - top-level OrExpression must produce combinator 'OR'"