fix: surface reviewer response failures

backend/src/bridge/session-bridge.ts

@@ -1,5 +1,19 @@
 import type { RpcClient } from "../rpc/rpc-client.js";
 
+const GENERIC_MODEL_FAILURE =
+  "Model request failed. Check provider connectivity, then Resume the session.";
+const SUBSCRIPTION_MODEL_FAILURE =
+  "The selected model is unavailable for the current subscription. Choose another model and start a new session.";
+
+function safeModelFailure(error: unknown): string {
+  const detail = typeof error === "string" ? error : "";
+  const isSubscriptionFailure =
+    /\b429\b/.test(detail) &&
+    /(subscription plan|code["':\s]+1311|does not yet include access)/i.test(detail);
+
+  return isSubscriptionFailure ? SUBSCRIPTION_MODEL_FAILURE : GENERIC_MODEL_FAILURE;
+}
+
 export type ToolActivity = {
   kind: "tool";
   toolCallId: string;
@@ -53,7 +67,7 @@ export class SessionBridge {
           this.fan({
             type: "info",
             level: "error",
-            text: "Model request failed. Check provider connectivity, then Resume the session.",
+            text: safeModelFailure(m.message.errorMessage),
           });
         }
       } else if (m.type === "extension_ui_request" && m.method === "notify") {