test: cover billing override on HTTP 401

src/agents/failover-error.test.ts

@@ -527,6 +527,15 @@ describe("failover-error", () => {
     ).toBe("billing");
   });
 
+  it("401 billing-style message returns billing instead of generic auth", () => {
+    expect(
+      resolveFailoverReasonFromError({
+        status: 401,
+        message: "401 Key limit exceeded (monthly limit)",
+      }),
+    ).toBe("billing");
+  });
+
   it("resolveFailoverStatus maps auth_permanent to 403", () => {
     expect(resolveFailoverStatus("auth_permanent")).toBe(403);
   });

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

@@ -570,6 +570,12 @@ describe("classifyFailoverReasonFromHttpStatus", () => {
     ).toBeNull();
   });
 
+  it("lets billing-classified HTTP 401 responses bypass generic auth", () => {
+    expect(
+      classifyFailoverReasonFromHttpStatus(401, "401 Key limit exceeded (monthly limit)"),
+    ).toBe("billing");
+  });
+
   it("treats HTTP 499 as transient for structured errors", () => {
     expect(classifyFailoverReasonFromHttpStatus(499)).toBe("timeout");
     expect(classifyFailoverReasonFromHttpStatus(499, "499 Client Closed Request")).toBe("timeout");