fix(email): prevent double email for free users at 80%, fix subject line

Author: waleedlatif1

apps/sim/components/emails/subjects.ts

@@ -51,7 +51,7 @@ export function getEmailSubject(type: EmailSubjectType): string {
     case 'usage-threshold':
       return `You're nearing your monthly budget on ${brandName}`
     case 'free-tier-upgrade':
-      return `You're at 90% of your free credits on ${brandName}`
+      return `You're at 80% of your free credits on ${brandName}`
     case 'plan-welcome-pro':
       return `Your Pro plan is now active on ${brandName}`
     case 'plan-welcome-team':

apps/sim/lib/billing/core/usage.ts

@@ -715,18 +715,16 @@ export async function maybeSendUsageThresholdEmail(params: {
     const baseUrl = getBaseUrl()
     const isFreeUser = params.planName === 'Free'
 
-    // Check for 80% threshold (all users)
+    // Check for 80% threshold (paid users only — free users get a more specific email below)
     const crosses80 = params.percentBefore < 80 && params.percentAfter >= 80
-    // Check for 80% threshold (free users only)
-    const crosses80Free = params.percentBefore < 80 && params.percentAfter >= 80
     // Check for 100% threshold (free users only — credits exhausted)
     const crosses100 = params.percentBefore < 100 && params.percentAfter >= 100
 
     // Skip if no thresholds crossed
-    if (!crosses80 && !crosses80Free && !crosses100) return
+    if (!crosses80 && !crosses100) return
 
-    // For 80% threshold email (all users)
-    if (crosses80) {
+    // For 80% threshold email (paid users only)
+    if (crosses80 && !isFreeUser) {
       const ctaLink = `${baseUrl}/workspace?billing=usage`
       const sendTo = async (email: string, name?: string) => {
         const prefs = await getEmailPreferences(email)
@@ -781,7 +779,7 @@ export async function maybeSendUsageThresholdEmail(params: {
     }
 
     // For 80% threshold email (free users only)
-    if (crosses80Free && isFreeUser) {
+    if (crosses80 && isFreeUser) {
       const upgradeLink = `${baseUrl}/workspace?billing=upgrade`
       const sendFreeTierEmail = async (email: string, name?: string) => {
         const prefs = await getEmailPreferences(email)