test(a2a): cover registry version resolution; exclude optional-import guards from coverage

litellm/llms/a2a/chat/transformation.py

@@ -266,7 +266,7 @@ class A2AConfig(BaseConfig):
             from litellm.proxy.agent_endpoints.agent_registry import (
                 global_agent_registry,
             )
-        except ImportError:
+        except ImportError:  # pragma: no cover - registry only exists in a proxy context
             return None
 
         agent = global_agent_registry.get_agent_by_name(agent_name)
@@ -288,7 +288,7 @@ class A2AConfig(BaseConfig):
                 to_core_send_message_request,
             )
             from a2a.compat.v0_3.types import MessageSendParams, SendMessageRequest
-        except ImportError as e:
+        except ImportError as e:  # pragma: no cover - a2a-sdk is an optional dependency
             raise A2AError(
                 status_code=500,
                 message=(

tests/test_litellm/llms/a2a/chat/test_a2a_chat_transformation.py

@@ -99,6 +99,31 @@ def test_transform_request_reads_pinned_version_from_registry():
         global_agent_registry.agent_list = original_agents
 
 
+def test_transform_request_registry_agent_without_pinned_version_uses_0_3():
+    """An agent whose card omits ``protocolVersion`` keeps the legacy 0.3 method."""
+    try:
+        from litellm.proxy.agent_endpoints.agent_registry import global_agent_registry
+        from litellm.types.agents import AgentResponse
+    except ImportError:
+        import pytest
+
+        pytest.skip("Registry not available (not in proxy context)")
+
+    agent = AgentResponse(
+        agent_id="legacy-id",
+        agent_name="legacy-agent",
+        agent_card_params={"url": "http://agent.example.com:9999"},
+        litellm_params={},
+    )
+    original_agents = global_agent_registry.agent_list.copy()
+    global_agent_registry.register_agent(agent)
+    try:
+        request = A2AConfig().transform_request("legacy-agent", _MESSAGES, {}, {}, {})
+        assert request["method"] == "message/send"
+    finally:
+        global_agent_registry.agent_list = original_agents
+
+
 def test_transform_response_extracts_text_from_v1_message():
     """Regression for #32609: text must be extracted from a 1.0 protobuf-JSON
     message result whose parts carry no ``kind`` field."""