fix(agents): classify upstream transport errors as fallback-worthy (#95519)

maweibin · claude · maweibin · commit ed6dd665433d · 2026-06-25T09:30:27.000+08:00
classifyBusinessDenialErrorPayloadReason now also returns timeout,
overloaded, and server_error failover reasons, so provider upstream
errors (e.g. HTTP 500, timeout, overloaded) correctly trigger model
fallback instead of being silently ignored.

Co-Authored-By: Claude Sonnet 4.6 &lt;noreply@anthropic.com&gt;
diff --git a/src/agents/embedded-agent-runner/result-fallback-classifier.test.ts b/src/agents/embedded-agent-runner/result-fallback-classifier.test.ts
@@ -282,7 +282,7 @@ describe("classifyEmbeddedAgentRunResultForModelFallback", () => {
     expect(result).toBeNull();
   });
 
-  it("does not retry non-business transport error payloads", () => {
+  it("retries transport error payloads as fallback-worthy", () => {
     const result = classifyEmbeddedAgentRunResultForModelFallback({
       provider: "custom",
       model: "llama-3.1",
@@ -299,7 +299,12 @@ describe("classifyEmbeddedAgentRunResultForModelFallback", () => {
       },
     });
 
-    expect(result).toBeNull();
+    expect(result).toEqual({
+      message: "custom/llama-3.1 ended with a provider error: HTTP 500: internal server error",
+      reason: "timeout",
+      code: "embedded_error_payload",
+      rawError: "HTTP 500: internal server error",
+    });
   });
 
   it("keeps tool-authored incomplete summaries fallback-eligible", () => {
diff --git a/src/agents/embedded-agent-runner/result-fallback-classifier.ts b/src/agents/embedded-agent-runner/result-fallback-classifier.ts
@@ -150,7 +150,10 @@ function classifyHarnessResult(params: {
 function classifyBusinessDenialErrorPayloadReason(
   errorText: string,
   provider: string,
-): Extract<FailoverReason, "auth" | "auth_permanent" | "billing" | "rate_limit"> | null {
+): Extract<
+  FailoverReason,
+  "auth" | "auth_permanent" | "billing" | "rate_limit" | "timeout" | "overloaded" | "server_error"
+> | null {
   if (!errorText.trim()) {
     return null;
   }
@@ -160,6 +163,9 @@ function classifyBusinessDenialErrorPayloadReason(
     case "auth_permanent":
     case "billing":
     case "rate_limit":
+    case "timeout":
+    case "overloaded":
+    case "server_error":
       return failoverReason;
     default:
       return null;
