diff --git a/packages/ai/src/provider-error.ts b/packages/ai/src/provider-error.ts
index dcdf68aeb39..000e0d40d3b 100644
--- a/packages/ai/src/provider-error.ts
+++ b/packages/ai/src/provider-error.ts
@@ -109,7 +109,8 @@ const QUOTA_CODES = new Set([
   "freeusagelimiterror",
   "creditlimitexceeded",
 ])
-const AUTH_CODES = new Set(["authentication_error", "permission_error"])
+// Google reports an invalid API key as HTTP 400 INVALID_ARGUMENT with this `details[].reason`.
+const AUTH_CODES = new Set(["authentication_error", "permission_error", "api_key_invalid"])
 const SERVER_CODES = new Set([
   "api_error",
   "internal_error",
@@ -259,6 +260,10 @@ function providerCodes(value: unknown) {
     error?.type,
     error?.status,
     error?.error_type,
+    // Google `google.rpc.ErrorInfo` details carry the specific reason.
+    ...(Array.isArray(error?.details)
+      ? error.details.map((detail) => (isRecord(detail) ? detail.reason : undefined))
+      : []),
     inner?.code,
     metadata?.error_type,
     responseError?.code,
diff --git a/packages/ai/test/provider-error.test.ts b/packages/ai/test/provider-error.test.ts
index 66001973931..457f8a4de8b 100644
--- a/packages/ai/test/provider-error.test.ts
+++ b/packages/ai/test/provider-error.test.ts
@@ -355,6 +355,32 @@ describe("provider error rawBody classification", () => {
     }
   })
 
+  test("classifies Google invalid API keys as authentication failures", () => {
+    const rawBody = JSON.stringify({
+      error: {
+        code: 400,
+        message: "API key not valid. Please pass a valid API key.",
+        status: "INVALID_ARGUMENT",
+        details: [
+          {
+            "@type": "type.googleapis.com/google.rpc.ErrorInfo",
+            reason: "API_KEY_INVALID",
+            domain: "googleapis.com",
+          },
+          {
+            "@type": "type.googleapis.com/google.rpc.LocalizedMessage",
+            locale: "en-US",
+            message: "API key not valid. Please pass a valid API key.",
+          },
+        ],
+      },
+    })
+    expect(
+      classifyProviderFailure({ message: "API key not valid. Please pass a valid API key.", status: 400, rawBody })
+        ._tag,
+    ).toBe("Authentication")
+  })
+
   test("classifies overflow signals buried in the raw payload when the summary is vague", () => {
     const reason = classifyProviderFailure({
       message: "Request failed",