From e7136005ebc06e635d609f144df4f903b9076735 Mon Sep 17 00:00:00 2001
From: Vincent Koc <vincentkoc@ieee.org>
Date: Wed, 10 Jun 2026 23:33:57 +0900
Subject: [PATCH] fix(types): narrow provider auth metadata

---
 src/llm/providers/anthropic.ts | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/llm/providers/anthropic.ts b/src/llm/providers/anthropic.ts
index 4f6fb964210b..23b4a03106b2 100644
--- a/src/llm/providers/anthropic.ts
+++ b/src/llm/providers/anthropic.ts
@@ -945,7 +945,11 @@ function createClient(
     return { client, isOAuthToken: false };
   }
 
-  if (model.provider === "microsoft-foundry" && model.authHeader === true) {
+  const foundryAuthHeader =
+    model.provider === "microsoft-foundry"
+      ? (model as Model<"anthropic-messages"> & { authHeader?: unknown }).authHeader
+      : undefined;
+  if (foundryAuthHeader === true) {
     const client = new Anthropic({
       apiKey: null,
       authToken: apiKey,