diff --git a/src/agents/failover-error.test.ts b/src/agents/failover-error.test.ts
index 38e3530f01..9f312d5c92 100644
--- a/src/agents/failover-error.test.ts
+++ b/src/agents/failover-error.test.ts
@@ -70,8 +70,8 @@ describe("failover-error", () => {
     expect(resolveFailoverReasonFromError({ status: 499 })).toBe("timeout");
     expect(resolveFailoverReasonFromError({ status: 400 })).toBe("format");
     expect(resolveFailoverReasonFromError({ status: 422 })).toBe("format");
-    // Keep the status-only path behavior-preserving and conservative.
-    expect(resolveFailoverReasonFromError({ status: 500 })).toBeNull();
+    // Transient server errors (500/502/503/504) should trigger failover as timeout.
+    expect(resolveFailoverReasonFromError({ status: 500 })).toBe("timeout");
     expect(resolveFailoverReasonFromError({ status: 502 })).toBe("timeout");
     expect(resolveFailoverReasonFromError({ status: 503 })).toBe("timeout");
     expect(resolveFailoverReasonFromError({ status: 504 })).toBe("timeout");
diff --git a/src/agents/pi-embedded-helpers/errors.ts b/src/agents/pi-embedded-helpers/errors.ts
index ff94ea5883..0167e7f8d0 100644
--- a/src/agents/pi-embedded-helpers/errors.ts
+++ b/src/agents/pi-embedded-helpers/errors.ts
@@ -494,7 +494,7 @@ export function classifyFailoverReasonFromHttpStatus(
     }
     return "timeout";
   }
-  if (status === 502 || status === 504) {
+  if (status === 500 || status === 502 || status === 504) {
     return "timeout";
   }
   if (status === 529) {