From 008f91d84b6ff239929a76af58b1b9d4b59556b3 Mon Sep 17 00:00:00 2001 From: Jeremiah Lowin <153965+jlowin@users.noreply.github.com> Date: Wed, 22 Apr 2026 09:30:37 -0400 Subject: [PATCH] fix: narrow _token_validator with isinstance for ty in AzureProvider.from_b2c (#4007) Co-authored-by: Claude --- src/fastmcp/server/auth/providers/azure.py | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/src/fastmcp/server/auth/providers/azure.py b/src/fastmcp/server/auth/providers/azure.py index 11d75db98..66b3c8a66 100644 --- a/src/fastmcp/server/auth/providers/azure.py +++ b/src/fastmcp/server/auth/providers/azure.py @@ -351,7 +351,8 @@ class AzureProvider(OAuthProxy): token_issuer=token_issuer, **kwargs, ) - provider._token_validator.issuer = token_issuer # type: ignore[union-attr] + if isinstance(provider._token_validator, JWTVerifier): + provider._token_validator.issuer = token_issuer provider._obo_supported = False return provider