chore(a2a): update host per AppSec recommendation (#619)

Co-authored-by: jer <jerebill@amazon.com>

Author: jer96

src/strands/multiagent/a2a/server.py

@@ -31,7 +31,7 @@ def __init__(
         agent: SAAgent,
         *,
         # AgentCard
-        host: str = "0.0.0.0",
+        host: str = "127.0.0.1",
         port: int = 9000,
         http_url: str | None = None,
         serve_at_root: bool = False,
@@ -42,13 +42,12 @@ def __init__(
         queue_manager: QueueManager | None = None,
         push_config_store: PushNotificationConfigStore | None = None,
         push_sender: PushNotificationSender | None = None,
-
     ):
         """Initialize an A2A-compatible server from a Strands agent.
 
         Args:
             agent: The Strands Agent to wrap with A2A compatibility.
-            host: The hostname or IP address to bind the A2A server to. Defaults to "0.0.0.0".
+            host: The hostname or IP address to bind the A2A server to. Defaults to "127.0.0.1".
             port: The port to bind the A2A server to. Defaults to 9000.
             http_url: The public HTTP URL where this agent will be accessible. If provided,
                 this overrides the generated URL from host/port and enables automatic

tests/strands/multiagent/a2a/test_server.py

@@ -22,9 +22,9 @@ def test_a2a_agent_initialization(mock_strands_agent):
     assert a2a_agent.strands_agent == mock_strands_agent
     assert a2a_agent.name == "Test Agent"
     assert a2a_agent.description == "A test agent for unit testing"
-    assert a2a_agent.host == "0.0.0.0"
+    assert a2a_agent.host == "127.0.0.1"
     assert a2a_agent.port == 9000
-    assert a2a_agent.http_url == "http://0.0.0.0:9000/"
+    assert a2a_agent.http_url == "http://127.0.0.1:9000/"
     assert a2a_agent.version == "0.0.1"
     assert isinstance(a2a_agent.capabilities, AgentCapabilities)
     assert len(a2a_agent.agent_skills) == 1
@@ -85,7 +85,7 @@ def test_public_agent_card(mock_strands_agent):
     assert isinstance(card, AgentCard)
     assert card.name == "Test Agent"
     assert card.description == "A test agent for unit testing"
-    assert card.url == "http://0.0.0.0:9000/"
+    assert card.url == "http://127.0.0.1:9000/"
     assert card.version == "0.0.1"
     assert card.default_input_modes == ["text"]
     assert card.default_output_modes == ["text"]
@@ -448,7 +448,7 @@ def test_serve_with_starlette(mock_run, mock_strands_agent):
     mock_run.assert_called_once()
     args, kwargs = mock_run.call_args
     assert isinstance(args[0], Starlette)
-    assert kwargs["host"] == "0.0.0.0"
+    assert kwargs["host"] == "127.0.0.1"
     assert kwargs["port"] == 9000
 
 
@@ -462,7 +462,7 @@ def test_serve_with_fastapi(mock_run, mock_strands_agent):
     mock_run.assert_called_once()
     args, kwargs = mock_run.call_args
     assert isinstance(args[0], FastAPI)
-    assert kwargs["host"] == "0.0.0.0"
+    assert kwargs["host"] == "127.0.0.1"
     assert kwargs["port"] == 9000