Why does my AI-built app break when I add Stripe?
Diagnose checkout, webhook, and paid-access failures in an AI-built application.
When checkout works but paid access does not, trace the journey from the server creating Checkout through Stripe's payment result, webhook delivery, stored state, and the server's access check. An AI-generated app may contain any of the same integration mistakes as hand-written code. A success redirect alone does not prove that payment was received or access was saved.
Find the first broken link
Use Stripe test mode and a disposable test account in your application. Record the Checkout Session ID, the signed-in application's user ID, the provider customer and subscription IDs if present, and the expected plan. Do not put secret keys or customer details in public logs. Check Stripe's event delivery details and your server logs for the same attempt.
| Symptom | Inspect first | Expected result |
|---|---|---|
| Checkout will not open | Server error, test/live mode, selected price and provider account | A server-created session for an allowed price in the same mode |
| Payment succeeds, access stays locked | Webhook delivery, signature, persistence and account mapping | A verified event leads to stored state for the right user |
| Access appears before payment | Redirect handler and server authorization | Access stays closed until the server confirms the relevant payment state |
| Access changes twice or reverts | Duplicate and out-of-order delivery handling | Repeated delivery converges on the correct state without duplicate effects |
| One user receives another's access | Customer-to-user mapping and server query | Each request checks the authenticated user's own entitlement |
Stripe's fulfillment guidance explains why webhook-based fulfillment is necessary even when a customer never reaches the success page. The complete Next.js billing guide builds the integration; this page helps you locate a failure in one you already have.
Signature verification fails
A webhook endpoint must verify the signature using the endpoint's own signing secret and the unmodified request body. Parsing and reserializing JSON before verification can change the bytes. Stripe documents the raw-body requirement and signature troubleshooting. Check that the request reached the intended endpoint and that its signing secret matches the listener or hosted destination sending the event. Never print the secret while debugging.
A successful signature check is only the start: handle the relevant event, map it to the correct account, persist the result, and return a failure if required processing did not complete so delivery can be retried. Check the endpoint's response and the stored record, not just a log saying an event arrived.
The payment is recorded but the wrong plan or user is shown
Compare the selected application offer with the Price ID used to create the session. The server should choose from its own allowed catalog after validating the requested offer; do not trust a browser-supplied amount or arbitrary price as the authorization rule. Test and live catalogs are separate. Check the actual Stripe account and mode before changing IDs.
Then trace the customer mapping from the authenticated application user to the Stripe customer and the persisted subscription or purchase. A webhook may be valid yet not identify the intended account. Decide what happens for an unknown customer: do not silently assign a purchase to whichever user happens to be in the browser.
Access works briefly, twice, or for the wrong person
Stripe can retry webhook deliveries and does not guarantee event ordering; see its webhook delivery guidance. Make processing safe for repeated events and avoid applying stale state over newer state. A common approach is to record processed event IDs for one-time effects and reconcile the current provider object when handling subscription changes. The database write and any effects must be designed together: recording an event before a failed write can otherwise suppress a needed retry.
Protect the paid API or server-rendered data with an authorization check for the current user and stored entitlement. Hiding a button or setting a client-side paid flag only changes the interface. Test an unpaid account, a paid account, cancellation, a repeated delivery, and a direct request to the protected endpoint. Verify the expected allow or deny result and the persisted state for each.
Hikari's source provides one inspectable example for individual subscription access: verified events update persisted subscription state and server access checks consume it. CoreMVP adds supported lifetime and shared-organization paths; its documentation helps you configure the foundation, while your own product still needs its own entitlement rules and tests.