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") {

backend/test/session-bridge.test.ts

@@ -105,6 +105,30 @@ test("assistant provider errors are sanitized and leave the turn failed", () =>
   expect(JSON.stringify(seen)).not.toContain("DO_NOT_LEAK");
 });
 
+test("subscription model errors become a safe actionable client message", () => {
+  const { rpc, fire } = fakeRpc();
+  const bridge = new SessionBridge(rpc);
+  const seen: any[] = [];
+  bridge.onClientEvent((event) => seen.push(event));
+
+  fire({
+    type: "message_end",
+    message: {
+      role: "assistant",
+      stopReason: "error",
+      errorMessage: "429: {\"code\":\"1311\",\"message\":\"Your current subscription plan does not yet include access to GLM-5.3\",\"secret\":\"DO_NOT_LEAK\"}",
+    },
+  });
+
+  expect(seen).toContainEqual({
+    type: "info",
+    level: "error",
+    text: "The selected model is unavailable for the current subscription. Choose another model and start a new session.",
+  });
+  expect(JSON.stringify(seen)).not.toContain("GLM-5.3");
+  expect(JSON.stringify(seen)).not.toContain("DO_NOT_LEAK");
+});
+
 test("markFailed records backend-detected failure without emitting raw detail", () => {
   const { rpc } = fakeRpc();
   const bridge = new SessionBridge(rpc);