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Python A2A: Expose supported_protocol_bindings as configurable parameter (#6098)

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* Expose supported_protocol_bindings as configurable parameter on A2AAgent

Add supported_protocol_bindings parameter to A2AAgent.__init__() allowing
users to configure which A2A protocol bindings (JSONRPC, GRPC, HTTP+JSON)
the client prefers when connecting to remote agents.

- Defaults to ["JSONRPC"] matching current behavior
- Passes through to ClientConfig for transport negotiation
- Replaces 4 hardcoded references with the configurable value

Closes #6057

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Fix empty list falsy trap and add fallback path test coverage

- Use 'is not None' check instead of 'or' to preserve explicit empty list
- Add test verifying empty list is not silently replaced with defaults
- Add test verifying fallback path uses custom bindings

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Document known protocol binding values in docstring

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Use Literal union for protocol binding type hint

Provides IDE autocomplete for known values while keeping the type
open for custom bindings (Literal is str at runtime).

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

---------

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
This commit is contained in:
Giles Odigwe
2026-05-28 12:05:13 -07:00
committed by GitHub
Unverified
parent d2f79930d5
commit e9a606344a
2 changed files with 97 additions and 5 deletions
Download Patch File Download Diff File Expand all files Collapse all files
python/packages/a2a/agent_framework_a2a/_agent.py
+9 -4
View File
@@ -176,6 +176,7 @@ class A2AAgent(AgentTelemetryLayer, BaseAgent):
http_client: httpx.AsyncClient | None = None,
auth_interceptor: AuthInterceptor | None = None,
timeout: float | httpx.Timeout | None = None,
supported_protocol_bindings: list[Literal["JSONRPC", "GRPC", "HTTP+JSON"] | str] | None = None,
**kwargs: Any,
) -> None:
"""Initialize the A2AAgent.
@@ -193,6 +194,9 @@ class A2AAgent(AgentTelemetryLayer, BaseAgent):
timeout: Request timeout configuration. Can be a float (applied to all timeout components),
httpx.Timeout object (for full control), or None (uses 10.0s connect, 60.0s read,
10.0s write, 5.0s pool - optimized for A2A operations).
supported_protocol_bindings: List of protocol bindings to use for transport negotiation.
Known values: "JSONRPC", "GRPC", "HTTP+JSON". Defaults to ["JSONRPC"].
The A2A spec treats this as an open-form string, so custom bindings are also accepted.
kwargs: any additional properties, passed to BaseAgent.
"""
# Default name/description from agent_card when not explicitly provided
@@ -205,6 +209,7 @@ class A2AAgent(AgentTelemetryLayer, BaseAgent):
super().__init__(id=id, name=name, description=description, **kwargs)
self._http_client: httpx.AsyncClient | None = http_client
self._timeout_config = self._create_timeout_config(timeout)
bindings = supported_protocol_bindings if supported_protocol_bindings is not None else ["JSONRPC"]
if client is not None:
self.client = client
self._non_streaming_client: Client | None = None
@@ -214,7 +219,7 @@ class A2AAgent(AgentTelemetryLayer, BaseAgent):
if url is None:
raise ValueError("Either agent_card or url must be provided")
# Create minimal agent card from URL
agent_card = minimal_agent_card(url, ["JSONRPC"])
agent_card = minimal_agent_card(url, bindings)
# Create or use provided httpx client
if http_client is None:
@@ -229,13 +234,13 @@ class A2AAgent(AgentTelemetryLayer, BaseAgent):
streaming_config = ClientConfig(
httpx_client=http_client,
streaming=True,
supported_protocol_bindings=["JSONRPC"],
supported_protocol_bindings=bindings,
)
# Create non-streaming client (single request/response for stream=False)
non_streaming_config = ClientConfig(
httpx_client=http_client,
streaming=False,
supported_protocol_bindings=["JSONRPC"],
supported_protocol_bindings=bindings,
)
streaming_factory = ClientFactory(streaming_config)
non_streaming_factory = ClientFactory(non_streaming_config)
@@ -256,7 +261,7 @@ class A2AAgent(AgentTelemetryLayer, BaseAgent):
"Provide a 'url' argument or ensure 'agent_card.supported_interfaces' "
"contains at least one interface with a URL."
) from transport_error
fallback_card = minimal_agent_card(fallback_url, ["JSONRPC"])
fallback_card = minimal_agent_card(fallback_url, bindings)
try:
self.client = streaming_factory.create(fallback_card, interceptors=interceptors) # type: ignore
self._non_streaming_client = non_streaming_factory.create(
python/packages/a2a/tests/test_a2a_agent.py
+88 -1
View File
@@ -703,7 +703,94 @@ def test_a2a_agent_initialization_with_timeout_parameter() -> None:
assert isinstance(timeout_arg, httpx.Timeout)
# region Continuation Token Tests
def test_a2a_agent_initialization_with_supported_protocol_bindings() -> None:
"""Test A2AAgent initialization with custom supported_protocol_bindings."""
with (
patch("agent_framework_a2a._agent.httpx.AsyncClient") as mock_async_client,
patch("agent_framework_a2a._agent.ClientConfig") as mock_config,
patch("agent_framework_a2a._agent.ClientFactory") as mock_factory,
):
mock_async_client.return_value = MagicMock()
mock_client_instance = MagicMock()
mock_factory.return_value.create.return_value = mock_client_instance
A2AAgent(
name="Test Agent",
url="https://test-agent.example.com",
supported_protocol_bindings=["GRPC", "JSONRPC"],
)
# Verify ClientConfig was called with our custom bindings for both streaming and non-streaming
assert mock_config.call_count == 2
for call in mock_config.call_args_list:
assert call.kwargs["supported_protocol_bindings"] == ["GRPC", "JSONRPC"]
def test_a2a_agent_initialization_defaults_to_jsonrpc() -> None:
"""Test A2AAgent defaults to JSONRPC when supported_protocol_bindings is not provided."""
with (
patch("agent_framework_a2a._agent.httpx.AsyncClient") as mock_async_client,
patch("agent_framework_a2a._agent.ClientConfig") as mock_config,
patch("agent_framework_a2a._agent.ClientFactory") as mock_factory,
):
mock_async_client.return_value = MagicMock()
mock_client_instance = MagicMock()
mock_factory.return_value.create.return_value = mock_client_instance
A2AAgent(name="Test Agent", url="https://test-agent.example.com")
# Verify ClientConfig was called with default JSONRPC bindings
assert mock_config.call_count == 2
for call in mock_config.call_args_list:
assert call.kwargs["supported_protocol_bindings"] == ["JSONRPC"]
def test_a2a_agent_initialization_empty_list_preserved() -> None:
"""Test that an explicit empty list is preserved and not replaced with defaults."""
with (
patch("agent_framework_a2a._agent.httpx.AsyncClient") as mock_async_client,
patch("agent_framework_a2a._agent.ClientConfig") as mock_config,
patch("agent_framework_a2a._agent.ClientFactory") as mock_factory,
):
mock_async_client.return_value = MagicMock()
mock_client_instance = MagicMock()
mock_factory.return_value.create.return_value = mock_client_instance
A2AAgent(
name="Test Agent",
url="https://test-agent.example.com",
supported_protocol_bindings=[],
)
# Verify ClientConfig was called with the explicit empty list, not the default
assert mock_config.call_count == 2
for call in mock_config.call_args_list:
assert call.kwargs["supported_protocol_bindings"] == []
def test_a2a_agent_fallback_uses_custom_bindings() -> None:
"""Test that transport fallback path uses custom bindings."""
mock_agent_card = MagicMock()
mock_agent_card.supported_interfaces = [MagicMock(url="https://fallback.example.com")]
mock_factory = MagicMock()
# First create() call fails (primary streaming), then fallback calls succeed
primary_error = Exception("no compatible transports found")
mock_factory.create.side_effect = [primary_error, MagicMock(), MagicMock()]
with (
patch("agent_framework_a2a._agent.ClientFactory", return_value=mock_factory),
patch("agent_framework_a2a._agent.minimal_agent_card") as mock_minimal_card,
patch("agent_framework_a2a._agent.httpx.AsyncClient"),
):
A2AAgent(
name="test-agent",
agent_card=mock_agent_card,
supported_protocol_bindings=["GRPC", "HTTP+JSON"],
)
# Verify minimal_agent_card was called with the custom bindings
mock_minimal_card.assert_called_once_with("https://fallback.example.com", ["GRPC", "HTTP+JSON"])
async def test_working_task_emits_continuation_token(a2a_agent: A2AAgent, mock_a2a_client: MockA2AClient) -> None: