fix(a2a): accept semver protocolVersion values like 0.3.0 in agent cards

litellm/proxy/a2a/agent_card.py

@@ -8,22 +8,35 @@ and uses LiteLLM auth.
 """
 
 from copy import deepcopy
-from typing import Any, Dict, List, Mapping
+from typing import Any, Dict, List, Literal, Mapping
+
+SupportedA2AVersion = Literal["0.3", "1.0"]
 
 # Protocol versions LiteLLM can serve to A2A clients. The admin pins one per agent;
 # responses are normalized to it regardless of the upstream agent's own version.
-SUPPORTED_A2A_PROTOCOL_VERSIONS = ("0.3", "1.0")
+SUPPORTED_A2A_PROTOCOL_VERSIONS: tuple[SupportedA2AVersion, ...] = ("0.3", "1.0")
 
 # Default served version when the agent card does not pin one.
 LITELLM_A2A_PROTOCOL_VERSION = "1.0"
 
 
+def normalize_protocol_version(version: object) -> SupportedA2AVersion | None:
+    """Map a raw ``protocolVersion`` value to the supported canonical major.minor version.
+
+    Semver strings the A2A spec and Google a2a-sdk emit (e.g. ``"0.3.0"``, ``"1.0.1"``)
+    canonicalize to their major.minor (``"0.3"``, ``"1.0"``). Anything outside the
+    supported set, including non-strings, yields ``None``.
+    """
+    if not isinstance(version, str):
+        return None
+    major_minor = ".".join(version.split(".")[:2])
+    return next((supported for supported in SUPPORTED_A2A_PROTOCOL_VERSIONS if supported == major_minor), None)
+
+
 def resolve_served_protocol_version(card: Mapping[str, Any] | None) -> str:
     """Return the validated protocol version an agent card pins, else the default."""
-    version = card.get("protocolVersion") if card else None
-    if version in SUPPORTED_A2A_PROTOCOL_VERSIONS:
-        return version
-    return LITELLM_A2A_PROTOCOL_VERSION
+    normalized = normalize_protocol_version(card.get("protocolVersion") if card else None)
+    return normalized if normalized is not None else LITELLM_A2A_PROTOCOL_VERSION
 
 
 # Security scheme exposed by the LiteLLM-fronted agent card. Always replaces

litellm/proxy/a2a/version_convert.py

@@ -30,6 +30,7 @@ from typing import Callable, Literal, Union
 from pydantic import BaseModel
 
 from litellm._logging import verbose_proxy_logger
+from litellm.proxy.a2a.agent_card import normalize_protocol_version
 
 A2AVersion = Literal["0.3", "1.0"]
 RequestId = Union[str, int, None]
@@ -103,16 +104,14 @@ def normalize_request_params(params: JsonDict, served: A2AVersion, *, method: st
 def _detect_card_version(card: JsonDict) -> A2AVersion:
     """Infer the wire version of an agent card dict.
 
-    ``protocolVersion`` is the authoritative indicator; fall back to presence of
-    ``supportedInterfaces`` (a 1.0-only field) only when the explicit field is absent.
-    Cards that set ``protocolVersion: "0.3"`` or carry neither signal are treated as 0.3.
+    ``protocolVersion`` is the authoritative indicator; semver values normalize to
+    their major.minor (``"0.3.0"`` -> ``"0.3"``). Fall back to presence of
+    ``supportedInterfaces`` (a 1.0-only field) only when the explicit field is
+    absent or unrecognized; cards carrying neither signal are treated as 0.3.
     """
-    pv = card.get("protocolVersion")
-    if pv == "1.0":
-        return "1.0"
-    if pv == "0.3":
-        return "0.3"
-    # No protocolVersion field: use structural heuristic.
+    normalized = normalize_protocol_version(card.get("protocolVersion"))
+    if normalized is not None:
+        return normalized
     return "1.0" if "supportedInterfaces" in card else "0.3"
 
 

litellm/proxy/agent_endpoints/endpoints.py

@@ -23,6 +23,7 @@ from litellm.proxy._types import CommonProxyErrors, LitellmUserRoles, UserAPIKey
 from litellm.proxy.a2a.agent_card import (
     SUPPORTED_A2A_PROTOCOL_VERSIONS,
     merge_agent_card,
+    normalize_protocol_version,
 )
 from litellm.proxy.auth.user_api_key_auth import user_api_key_auth
 from litellm.proxy.common_utils.rbac_utils import check_feature_access_for_user
@@ -51,7 +52,7 @@ def _proxy_base_url(http_request: Request) -> str:
 def _validate_protocol_version(upstream_card: Mapping[str, Any] | None) -> None:
     """Reject an agent card pinning an unsupported A2A protocol version."""
     version = upstream_card.get("protocolVersion") if upstream_card else None
-    if version is not None and version not in SUPPORTED_A2A_PROTOCOL_VERSIONS:
+    if version is not None and normalize_protocol_version(version) is None:
         raise HTTPException(
             status_code=400,
             detail=(

tests/test_litellm/proxy/a2a/test_agent_card.py

@@ -1,10 +1,14 @@
 """Unit tests for the pure merge logic in litellm/proxy/a2a/agent_card.py."""
 
+import pytest
+
 from litellm.proxy.a2a.agent_card import (
     LITELLM_A2A_PROTOCOL_VERSION,
     LITELLM_SECURITY_REQUIREMENTS,
     LITELLM_SECURITY_SCHEMES,
     merge_agent_card,
+    normalize_protocol_version,
+    resolve_served_protocol_version,
 )
 
 PROXY_URL = "https://proxy.example/a2a/agent-xyz"
@@ -205,3 +209,47 @@ def test_strips_additional_interfaces_to_prevent_backend_url_leak():
     ]
     merged = merge_agent_card(upstream, proxy_url=PROXY_URL, proxy_base_url=PROXY_BASE)
     assert "additionalInterfaces" not in merged
+
+
+@pytest.mark.parametrize(
+    ("raw", "expected"),
+    [
+        ("0.3", "0.3"),
+        ("0.3.0", "0.3"),
+        ("1.0", "1.0"),
+        ("1.0.0", "1.0"),
+        ("1.0.1", "1.0"),
+        ("0.2.6", None),
+        ("2.0", None),
+        ("0.30", None),
+        ("garbage", None),
+        ("", None),
+        (None, None),
+        (1.0, None),
+    ],
+)
+def test_normalize_protocol_version(raw, expected):
+    assert normalize_protocol_version(raw) == expected
+
+
+def test_resolve_served_protocol_version_canonicalizes_semver_pins():
+    assert resolve_served_protocol_version({"protocolVersion": "0.3.0"}) == "0.3"
+    assert resolve_served_protocol_version({"protocolVersion": "1.0.0"}) == "1.0"
+    assert resolve_served_protocol_version({"protocolVersion": "0.3"}) == "0.3"
+    assert resolve_served_protocol_version({"protocolVersion": "1.0"}) == "1.0"
+
+
+def test_resolve_served_protocol_version_falls_back_for_unsupported():
+    assert (
+        resolve_served_protocol_version({"protocolVersion": "0.2.6"})
+        == LITELLM_A2A_PROTOCOL_VERSION
+    )
+    assert resolve_served_protocol_version(None) == LITELLM_A2A_PROTOCOL_VERSION
+
+
+def test_serves_semver_pinned_protocol_version_as_major_minor():
+    card = _full_upstream_card()
+    card["protocolVersion"] = "0.3.0"
+    merged = merge_agent_card(card, proxy_url=PROXY_URL, proxy_base_url=PROXY_BASE)
+    assert merged["protocolVersion"] == "0.3"
+    assert merged["supportedInterfaces"][0]["protocolVersion"] == "0.3"

tests/test_litellm/proxy/a2a/test_version_convert.py

@@ -313,3 +313,13 @@ def test_agent_card_with_0_3_pin_and_supported_interfaces_is_lowered():
 def test_agent_card_same_version_passthrough():
     card = _extended_card_1_0()
     assert normalize_agent_card(card, "1.0") is card
+
+
+def test_detect_card_version_normalizes_semver_protocol_version():
+    from litellm.proxy.a2a.version_convert import _detect_card_version
+
+    assert _detect_card_version({"protocolVersion": "1.0.0"}) == "1.0"
+    assert (
+        _detect_card_version({"protocolVersion": "0.3.0", "supportedInterfaces": []})
+        == "0.3"
+    )

tests/test_litellm/proxy/agent_endpoints/test_endpoints.py

@@ -540,6 +540,47 @@ class TestAgentRBACProxyAdmin:
             assert resp.status_code == 200
 
 
+class TestAgentProtocolVersionValidation:
+    """Registration accepts spec-default semver protocolVersion values and still
+    rejects genuinely unsupported versions."""
+
+    @pytest.fixture(autouse=True)
+    def _setup(self, monkeypatch):
+        self.admin_client = _make_app_with_role(LitellmUserRoles.PROXY_ADMIN)
+        self.mock_registry = MagicMock()
+        monkeypatch.setattr(agent_endpoints, "AGENT_REGISTRY", self.mock_registry)
+
+    def _create_agent_with_protocol_version(self, protocol_version: str):
+        config = _sample_agent_config()
+        config["agent_card_params"]["protocolVersion"] = protocol_version
+        with patch("litellm.proxy.proxy_server.prisma_client"):
+            self.mock_registry.get_agent_by_name = MagicMock(return_value=None)
+            self.mock_registry.add_agent_to_db = AsyncMock(
+                return_value=_sample_agent_response()
+            )
+            self.mock_registry.register_agent = MagicMock()
+            return self.admin_client.post(
+                "/v1/agents",
+                json=config,
+                headers={"Authorization": "Bearer k"},
+            )
+
+    def test_semver_protocol_version_registers_and_stores_major_minor(self):
+        resp = self._create_agent_with_protocol_version("0.3.0")
+        assert resp.status_code == 200
+        stored_card = self.mock_registry.add_agent_to_db.await_args.kwargs["agent"][
+            "agent_card_params"
+        ]
+        assert stored_card["protocolVersion"] == "0.3"
+        assert stored_card["supportedInterfaces"][0]["protocolVersion"] == "0.3"
+
+    def test_unsupported_protocol_version_is_rejected(self):
+        resp = self._create_agent_with_protocol_version("0.2.6")
+        assert resp.status_code == 400
+        assert "Unsupported protocolVersion '0.2.6'" in resp.json()["detail"]
+        self.mock_registry.add_agent_to_db.assert_not_awaited()
+
+
 class TestCheckAgentManagementPermission:
     """Unit tests for the _check_agent_management_permission helper."""