fix(failover): narrow service-unavailable to require overload indicator

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

@@ -540,13 +540,22 @@ describe("classifyFailoverReason", () => {
         "This model is currently experiencing high demand. Please try again later.",
       ),
     ).toBe("rate_limit");
-    expect(classifyFailoverReason("LLM error: service unavailable")).toBe("rate_limit");
+    // "service unavailable" combined with overload indicator → rate_limit
+    expect(
+      classifyFailoverReason("service unavailable due to high demand and overloaded servers"),
+    ).toBe("rate_limit");
     expect(
       classifyFailoverReason(
         '{"error":{"code":503,"message":"The model is overloaded. Please try later","status":"UNAVAILABLE"}}',
       ),
     ).toBe("rate_limit");
   });
+  it("does not classify bare 'service unavailable' as rate_limit (#32828)", () => {
+    // A generic "service unavailable" from a proxy/CDN should not trigger
+    // provider-overload failover — it may be a transient proxy error or an
+    // unrelated upstream failure.
+    expect(classifyFailoverReason("LLM error: service unavailable")).toBeNull();
+  });
   it("classifies permanent auth errors as auth_permanent", () => {
     expect(classifyFailoverReason("invalid_api_key")).toBe("auth_permanent");
     expect(classifyFailoverReason("Your api key has been revoked")).toBe("auth_permanent");

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

@@ -15,7 +15,10 @@ const ERROR_PATTERNS = {
   overloaded: [
     /overloaded_error|"type"\s*:\s*"overloaded_error"/i,
     "overloaded",
-    "service unavailable",
+    // Match "service unavailable" only when combined with an explicit overload
+    // indicator — a generic 503 from a proxy/CDN should not be classified as
+    // provider-overload (#32828).
+    /service[_ ]unavailable.*(?:overload|capacity|high[_ ]demand)|(?:overload|capacity|high[_ ]demand).*service[_ ]unavailable/i,
     "high demand",
   ],
   timeout: [