Fix client_credentials providers to set client_info in _initialize

The base class _initialize() loads client_info from storage, which
overwrites any value set in the constructor. Move client_info setup
to _initialize override so it's properly set after tokens are loaded.

Also update tests to call _initialize() before checking client_info.

Author: pcarleton

src/mcp/client/auth/extensions/client_credentials.py

@@ -66,8 +66,8 @@ def __init__(
             scope=scopes,
         )
         super().__init__(server_url, client_metadata, storage, None, None, 300.0)
-        # Set client_info directly - no need for dynamic registration
-        self.context.client_info = OAuthClientInformationFull(
+        # Store client_info to be set during _initialize - no dynamic registration needed
+        self._fixed_client_info = OAuthClientInformationFull(
             redirect_uris=None,
             client_id=client_id,
             client_secret=client_secret,
@@ -76,6 +76,12 @@ def __init__(
             scope=scopes,
         )
 
+    async def _initialize(self) -> None:
+        """Load stored tokens and set pre-configured client_info."""
+        self.context.current_tokens = await self.context.storage.get_tokens()
+        self.context.client_info = self._fixed_client_info
+        self._initialized = True
+
     async def _perform_authorization(self) -> httpx.Request:
         """Perform client_credentials authorization."""
         return await self._exchange_token_client_credentials()
@@ -275,15 +281,21 @@ def __init__(
         )
         super().__init__(server_url, client_metadata, storage, None, None, 300.0)
         self._assertion_provider = assertion_provider
-        # Set client_info directly - no need for dynamic registration
-        self.context.client_info = OAuthClientInformationFull(
+        # Store client_info to be set during _initialize - no dynamic registration needed
+        self._fixed_client_info = OAuthClientInformationFull(
             redirect_uris=None,
             client_id=client_id,
             grant_types=["client_credentials"],
             token_endpoint_auth_method="private_key_jwt",
             scope=scopes,
         )
 
+    async def _initialize(self) -> None:
+        """Load stored tokens and set pre-configured client_info."""
+        self.context.current_tokens = await self.context.storage.get_tokens()
+        self.context.client_info = self._fixed_client_info
+        self._initialized = True
+
     async def _perform_authorization(self) -> httpx.Request:
         """Perform client_credentials authorization with private_key_jwt."""
         return await self._exchange_token_client_credentials()

tests/client/auth/extensions/test_client_credentials.py

@@ -177,22 +177,27 @@ async def test_token_exchange_request_jwt(self, rfc7523_oauth_provider: RFC7523O
 class TestClientCredentialsOAuthProvider:
     """Test ClientCredentialsOAuthProvider."""
 
-    def test_init_sets_client_info(self, mock_storage: MockTokenStorage):
-        """Test that constructor sets client_info directly."""
+    @pytest.mark.anyio
+    async def test_init_sets_client_info(self, mock_storage: MockTokenStorage):
+        """Test that _initialize sets client_info."""
         provider = ClientCredentialsOAuthProvider(
             server_url="https://api.example.com",
             storage=mock_storage,
             client_id="test-client-id",
             client_secret="test-client-secret",
         )
 
+        # client_info is set during _initialize
+        await provider._initialize()
+
         assert provider.context.client_info is not None
         assert provider.context.client_info.client_id == "test-client-id"
         assert provider.context.client_info.client_secret == "test-client-secret"
         assert provider.context.client_info.grant_types == ["client_credentials"]
         assert provider.context.client_info.token_endpoint_auth_method == "client_secret_basic"
 
-    def test_init_with_scopes(self, mock_storage: MockTokenStorage):
+    @pytest.mark.anyio
+    async def test_init_with_scopes(self, mock_storage: MockTokenStorage):
         """Test that constructor accepts scopes."""
         provider = ClientCredentialsOAuthProvider(
             server_url="https://api.example.com",
@@ -202,9 +207,11 @@ def test_init_with_scopes(self, mock_storage: MockTokenStorage):
             scopes="read write",
         )
 
+        await provider._initialize()
         assert provider.context.client_info.scope == "read write"
 
-    def test_init_with_client_secret_post(self, mock_storage: MockTokenStorage):
+    @pytest.mark.anyio
+    async def test_init_with_client_secret_post(self, mock_storage: MockTokenStorage):
         """Test that constructor accepts client_secret_post auth method."""
         provider = ClientCredentialsOAuthProvider(
             server_url="https://api.example.com",
@@ -214,6 +221,7 @@ def test_init_with_client_secret_post(self, mock_storage: MockTokenStorage):
             token_endpoint_auth_method="client_secret_post",
         )
 
+        await provider._initialize()
         assert provider.context.client_info.token_endpoint_auth_method == "client_secret_post"
 
     @pytest.mark.anyio
@@ -270,8 +278,9 @@ async def test_exchange_token_without_scopes(self, mock_storage: MockTokenStorag
 class TestPrivateKeyJWTOAuthProvider:
     """Test PrivateKeyJWTOAuthProvider."""
 
-    def test_init_sets_client_info(self, mock_storage: MockTokenStorage):
-        """Test that constructor sets client_info directly."""
+    @pytest.mark.anyio
+    async def test_init_sets_client_info(self, mock_storage: MockTokenStorage):
+        """Test that _initialize sets client_info."""
 
         async def mock_assertion_provider(audience: str) -> str:
             return "mock-jwt"
@@ -283,6 +292,9 @@ async def mock_assertion_provider(audience: str) -> str:
             assertion_provider=mock_assertion_provider,
         )
 
+        # client_info is set during _initialize
+        await provider._initialize()
+
         assert provider.context.client_info is not None
         assert provider.context.client_info.client_id == "test-client-id"
         assert provider.context.client_info.grant_types == ["client_credentials"]