fix(agents): fail over on billing/credits errors

src/agents/pi-embedded-helpers.test.ts

@@ -4,6 +4,7 @@ import { describe, expect, it } from "vitest";
 import {
   buildBootstrapContextFiles,
   formatAssistantErrorText,
+  isBillingErrorMessage,
   isContextOverflowError,
   isMessagingToolDuplicate,
   normalizeTextForComparison,
@@ -215,6 +216,28 @@ describe("isContextOverflowError", () => {
   });
 });
 
+describe("isBillingErrorMessage", () => {
+  it("matches credit / payment failures", () => {
+    const samples = [
+      "Your credit balance is too low to access the Anthropic API.",
+      "insufficient credits",
+      "Payment Required",
+      "HTTP 402 Payment Required",
+      "plans & billing",
+      "billing: please upgrade your plan",
+    ];
+    for (const sample of samples) {
+      expect(isBillingErrorMessage(sample)).toBe(true);
+    }
+  });
+
+  it("ignores unrelated errors", () => {
+    expect(isBillingErrorMessage("rate limit exceeded")).toBe(false);
+    expect(isBillingErrorMessage("invalid api key")).toBe(false);
+    expect(isBillingErrorMessage("context length exceeded")).toBe(false);
+  });
+});
+
 describe("formatAssistantErrorText", () => {
   const makeAssistantError = (errorMessage: string): AssistantMessage =>
     ({