fix: normalize OAuth redirect URI URL subtypes

Author: he-yufeng

src/mcp/shared/auth.py

@@ -85,6 +85,13 @@ def _empty_string_optional_url_to_none(cls, v: object) -> object:
             return None
         return v
 
+    @field_validator("redirect_uris", mode="before")
+    @classmethod
+    def _normalize_redirect_uris(cls, v: object) -> object:
+        if isinstance(v, list):
+            return [str(uri) for uri in v]
+        return v
+
     def validate_scope(self, requested_scope: str | None) -> list[str] | None:
         if requested_scope is None:
             return None

tests/shared/test_auth.py

@@ -1,7 +1,7 @@
 """Tests for OAuth 2.0 shared code."""
 
 import pytest
-from pydantic import ValidationError
+from pydantic import AnyHttpUrl, AnyUrl, ValidationError
 
 from mcp.shared.auth import OAuthClientInformationFull, OAuthClientMetadata, OAuthMetadata
 
@@ -109,6 +109,18 @@ def test_valid_url_passes_through_unchanged():
     assert str(metadata.client_uri) == "https://udemy.com/"
 
 
+def test_redirect_uri_url_subtypes_are_normalized():
+    info = OAuthClientInformationFull(
+        client_id="abc123",
+        redirect_uris=[AnyHttpUrl("https://example.com/callback")],
+    )
+
+    incoming = AnyUrl("https://example.com/callback")
+
+    assert info.validate_redirect_uri(incoming) == incoming
+    assert info.model_dump(mode="json")["redirect_uris"] == ["https://example.com/callback"]
+
+
 def test_information_full_inherits_coercion():
     """OAuthClientInformationFull subclasses OAuthClientMetadata, so the
     same coercion applies to DCR responses parsed via the full model."""