diff --git a/packages/openai-adapters/src/apis/AnthropicUtils.test.ts b/packages/openai-adapters/src/apis/AnthropicUtils.test.ts
index 7ed572c8057..29e7f79c5b3 100644
--- a/packages/openai-adapters/src/apis/AnthropicUtils.test.ts
+++ b/packages/openai-adapters/src/apis/AnthropicUtils.test.ts
@@ -93,14 +93,14 @@ describe("getAnthropicHeaders", () => {
       expect(headers["api-key"]).toBeUndefined();
     });
 
-    it("uses api-key for Azure AI Foundry endpoint", () => {
+    it("uses x-api-key for Azure AI Foundry endpoint", () => {
       const headers = getAnthropicHeaders(
         "azure-key",
         false,
         "https://my-resource.services.ai.azure.com/anthropic",
       );
-      expect(headers["api-key"]).toBe("azure-key");
-      expect(headers["x-api-key"]).toBeUndefined();
+      expect(headers["x-api-key"]).toBe("azure-key");
+      expect(headers["api-key"]).toBeUndefined();
     });
 
     it("uses api-key for Azure Cognitive Services endpoint", () => {
diff --git a/packages/openai-adapters/src/apis/AnthropicUtils.ts b/packages/openai-adapters/src/apis/AnthropicUtils.ts
index 46b28e5785c..4e279a5ea82 100644
--- a/packages/openai-adapters/src/apis/AnthropicUtils.ts
+++ b/packages/openai-adapters/src/apis/AnthropicUtils.ts
@@ -78,7 +78,10 @@ export function getAnthropicHeaders(
     );
   }
 
-  const authHeaderName = isAzure ? "api-key" : "x-api-key";
+  const authHeaderName =
+    isAzure && apiBase?.toLowerCase().includes("cognitiveservices.azure.com")
+      ? "api-key"
+      : "x-api-key";
 
   const headers: Record<string, string> = {
     "Content-Type": "application/json",