Cancel a Stripe subscription that completes after the account is deleted

src/test/stripe-account-presence.test.ts

@@ -0,0 +1,18 @@
+import { describe, expect, it } from "vitest";
+import { accountPresence } from "../../supabase/functions/stripe-webhook/account-presence";
+
+describe("checkout after account deletion", () => {
+  it("keeps a checkout whose account is still there", () => {
+    expect(accountPresence({ user: { id: "user-1" } })).toBe("present");
+  });
+
+  it("treats a deleted account as missing so billing can be canceled", () => {
+    expect(accountPresence({ user: null, errorStatus: 404, errorMessage: "User not found" })).toBe("missing");
+    expect(accountPresence({ user: null, errorMessage: "User not found" })).toBe("missing");
+  });
+
+  it("retries when the account lookup itself failed", () => {
+    expect(accountPresence({ user: null, errorStatus: 500, errorMessage: "timeout" })).toBe("unknown");
+    expect(accountPresence({ user: null })).toBe("unknown");
+  });
+});

supabase/functions/stripe-webhook/account-presence.ts

@@ -0,0 +1,16 @@
+export type AccountPresence = "present" | "missing" | "unknown";
+
+/**
+ * A checkout can finish after the account is gone. Only an explicit
+ * not-found is safe to treat as deleted; anything else should retry.
+ */
+export function accountPresence(lookup: {
+  user: unknown;
+  errorStatus?: number | null;
+  errorMessage?: string | null;
+}): AccountPresence {
+  if (lookup.user) return "present";
+  const message = lookup.errorMessage ?? "";
+  if (lookup.errorStatus === 404 || /not found/i.test(message)) return "missing";
+  return "unknown";
+}

supabase/functions/stripe-webhook/index.ts

@@ -8,6 +8,7 @@ import {
   processWebhookEvent,
   webhookFailureResponse,
 } from "./webhook-event-lifecycle.ts";
+import { accountPresence, type AccountPresence } from "./account-presence.ts";
 
 // Validate required environment variables
 const STRIPE_SECRET_KEY = Deno.env.get("STRIPE_SECRET_KEY");
@@ -175,6 +176,19 @@ async function handleCheckoutCompleted(session: Stripe.Checkout.Session) {
 
   console.log(`[WEBHOOK] Checkout completed for user ${userId}, sub: ${subscriptionId}`);
 
+  // Deleting an account cancels billing it can see. A Checkout that finishes
+  // in that window would otherwise keep charging a subscription with no user,
+  // and the database insert fails forever. Cancel it and acknowledge the event.
+  const presence = await lookupAccount(userId);
+  if (presence === "unknown") {
+    throw new Error("Could not confirm the account for this checkout");
+  }
+  if (presence === "missing") {
+    console.warn(`[WEBHOOK] Checkout completed after the account was deleted; canceling ${subscriptionId}`);
+    await cancelSubscriptionIfPresent(subscriptionId);
+    return;
+  }
+
   // Fetch the full subscription from Stripe
   const subscription = await stripe.subscriptions.retrieve(subscriptionId);
 
@@ -217,6 +231,28 @@ async function handleCheckoutCompleted(session: Stripe.Checkout.Session) {
   console.log(`[WEBHOOK] User ${userId} upgraded to Pro`);
 }
 
+async function lookupAccount(userId: string): Promise<AccountPresence> {
+  const { data, error } = await supabase.auth.admin.getUserById(userId);
+  const status = error && typeof error === "object" && "status" in error && typeof error.status === "number"
+    ? error.status
+    : null;
+  return accountPresence({
+    user: data?.user ?? null,
+    errorStatus: status,
+    errorMessage: error?.message ?? null,
+  });
+}
+
+async function cancelSubscriptionIfPresent(subscriptionId: string): Promise<void> {
+  try {
+    await stripe.subscriptions.cancel(subscriptionId);
+  } catch (error) {
+    const code = error && typeof error === "object" && "code" in error ? String(error.code) : "";
+    if (code === "resource_missing") return;
+    throw error;
+  }
+}
+
 async function handlePaymentSucceeded(invoice: Stripe.Invoice) {
   const subscriptionId = invoice.subscription as string;
   if (!subscriptionId) return;