fix(webapp): absolute base marker wins over legacy-dollar heuristic

Author: kathiekiwi

apps/webapp/app/components/billing/billingAlertsFormat.ts

@@ -208,6 +208,11 @@ export function isLegacyDollarAmountField(
     return false;
   }
 
+  // The exact $1 absolute base marker always wins, even with levels below 100 (e.g. a $5 alert).
+  if (rawAmount === ABSOLUTE_ALERT_BASE_CENTS) {
+    return false;
+  }
+
   if (!Number.isFinite(rawAmount) || rawAmount < 10) {
     return false;
   }

apps/webapp/test/billingAlertsFormat.test.ts

@@ -163,6 +163,22 @@ describe("billingAlertsFormat", () => {
     );
   });
 
+  it("keeps seeded absolute defaults absolute when the plan limit is exactly $100", () => {
+    const normalized = normalizeBillingAlertsFromApi(
+      {
+        amount: 100,
+        emails: [],
+        alertLevels: [5, 100, 500, 1000, 2500],
+      },
+      { planLimitCents: 10_000, effectiveLimitCents: 10_000 }
+    );
+
+    expect(normalized.amount).toBe(1);
+    expect(storedAlertsToThresholds(normalized, "none", 10_000, 10_000)).toEqual([
+      5, 100, 500, 1000, 2500,
+    ]);
+  });
+
   it("normalizes cents-based alerts with whole-number levels when amount matches limit", () => {
     const normalized = normalizeBillingAlertsFromApi(
       {
@@ -186,14 +202,14 @@ describe("billingAlertsFormat", () => {
     expect(
       normalizeBillingAlertsFromApi(
         {
-          amount: 100,
+          amount: 300,
           emails: [],
           alertLevels: [10, 50, 80],
         },
-        { planLimitCents: 10_000, effectiveLimitCents: 10_000 }
+        { planLimitCents: 30_000, effectiveLimitCents: 30_000 }
       )
     ).toEqual({
-      amount: 100,
+      amount: 300,
       emails: [],
       alertLevels: [10, 50, 80],
     });