From 2ef6b00581fb66a16bf5bf4d45f6bd520c51cb2f Mon Sep 17 00:00:00 2001
From: Khushi Kathuria <khushi.kathuria@37848692.corp-partner.google.com>
Date: Mon, 13 Oct 2025 11:53:16 +0530
Subject: [PATCH] fix(client_library): External Authentication bug fix

---
 google/cloud/internal/unified_grpc_credentials.cc | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/google/cloud/internal/unified_grpc_credentials.cc b/google/cloud/internal/unified_grpc_credentials.cc
index b1c82e99f2586..ee8005dee59ec 100644
--- a/google/cloud/internal/unified_grpc_credentials.cc
+++ b/google/cloud/internal/unified_grpc_credentials.cc
@@ -121,10 +121,14 @@ std::shared_ptr<GrpcAuthenticationStrategy> CreateAuthenticationStrategy(
       grpc::SslCredentialsOptions ssl_options;
       auto cainfo = LoadCAInfo(options);
       if (cainfo) ssl_options.pem_root_certs = std::move(*cainfo);
-      result = std::make_unique<GrpcChannelCredentialsAuthentication>(
-          grpc::CompositeChannelCredentials(
-              grpc::SslCredentials(ssl_options),
-              GrpcExternalAccountCredentials(cfg)));
+    auto call_creds = GrpcExternalAccountCredentials(cfg);
+     auto channel_creds = grpc::SslCredentials(ssl_options);
+      if (call_creds) {
+        result = std::make_unique<GrpcChannelCredentialsAuthentication>(
+            grpc::CompositeChannelCredentials(channel_creds, call_creds));
+      } else {
+        result = std::make_unique<GrpcChannelCredentialsAuthentication>(channel_creds);
+      }
     }
     void visit(ApiKeyConfig const& cfg) override {
       result = std::make_unique<GrpcApiKeyAuthentication>(cfg.api_key());