fix(agents): classify insufficient_quota 400s as billing (#36783)

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

@@ -283,6 +283,11 @@ export function classifyFailoverReasonFromHttpStatus(
     return "rate_limit";
   }
   if (status === 400) {
+    // Some providers return quota/balance errors under HTTP 400, so do not
+    // let the generic format fallback mask an explicit billing signal.
+    if (message && isBillingErrorMessage(message)) {
+      return "billing";
+    }
     return "format";
   }
   return null;

src/agents/pi-embedded-helpers/failover-matches.ts

@@ -44,6 +44,7 @@ const ERROR_PATTERNS = {
     /["']?(?:status|code)["']?\s*[:=]\s*402\b|\bhttp\s*402\b|\berror(?:\s+code)?\s*[:=]?\s*402\b|\b(?:got|returned|received)\s+(?:a\s+)?402\b|^\s*402\s+payment/i,
     "payment required",
     "insufficient credits",
+    /insufficient[_ ]quota/i,
     "credit balance",
     "plans & billing",
     "insufficient balance",