fix(agents): handle overloaded failover separately (#38301)

* fix(agents): skip auth-profile failure on overload

* fix(agents): note overload auth-profile fallback fix

* fix(agents): classify overloaded failures separately

* fix(agents): back off before overload failover

* fix(agents): tighten overload probe and backoff state

* fix(agents): persist overloaded cooldown across runs

* fix(agents): tighten overloaded status handling

* test(agents): add overload regression coverage

* fix(agents): restore runner imports after rebase

* test(agents): add overload fallback integration coverage

* fix(agents): harden overloaded failover abort handling

* test(agents): tighten overload classifier coverage

* test(agents): cover all-overloaded fallback exhaustion

* fix(cron): retry overloaded fallback summaries

* fix(cron): treat HTTP 529 as overloaded retry

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

@@ -293,13 +293,17 @@ export function classifyFailoverReasonFromHttpStatus(
   if (status === 408) {
     return "timeout";
   }
-  // Keep the status-only path conservative and behavior-preserving.
-  // Message-path HTTP heuristics are broader and should not leak in here.
-  if (status === 502 || status === 503 || status === 504) {
+  if (status === 503) {
+    if (message && isOverloadedErrorMessage(message)) {
+      return "overloaded";
+    }
+    return "timeout";
+  }
+  if (status === 502 || status === 504) {
     return "timeout";
   }
   if (status === 529) {
-    return "rate_limit";
+    return "overloaded";
   }
   if (status === 400) {
     // Some providers return quota/balance errors under HTTP 400, so do not
@@ -854,13 +858,6 @@ export function classifyFailoverReason(raw: string): FailoverReason | null {
   if (isModelNotFoundErrorMessage(raw)) {
     return "model_not_found";
   }
-  if (isTransientHttpError(raw)) {
-    // Treat transient 5xx provider failures as retryable transport issues.
-    return "timeout";
-  }
-  if (isJsonApiInternalServerError(raw)) {
-    return "timeout";
-  }
   if (isPeriodicUsageLimitErrorMessage(raw)) {
     return isBillingErrorMessage(raw) ? "billing" : "rate_limit";
   }
@@ -868,7 +865,19 @@ export function classifyFailoverReason(raw: string): FailoverReason | null {
     return "rate_limit";
   }
   if (isOverloadedErrorMessage(raw)) {
-    return "rate_limit";
+    return "overloaded";
+  }
+  if (isTransientHttpError(raw)) {
+    // 529 is always overloaded, even without explicit overload keywords in the body.
+    const status = extractLeadingHttpStatus(raw.trim());
+    if (status?.code === 529) {
+      return "overloaded";
+    }
+    // Treat remaining transient 5xx provider failures as retryable transport issues.
+    return "timeout";
+  }
+  if (isJsonApiInternalServerError(raw)) {
+    return "timeout";
   }
   if (isCloudCodeAssistFormatError(raw)) {
     return "format";

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

@@ -5,6 +5,7 @@ export type FailoverReason =
   | "auth_permanent"
   | "format"
   | "rate_limit"
+  | "overloaded"
   | "billing"
   | "timeout"
   | "model_not_found"