[Bug] Stripe webhook returns HTTP 200 on processing failure, preventing Stripe retries

[rohansx]

Bug

The Stripe webhook handler in backend/core/billing/external/stripe/webhooks.py returns HTTP 200 with {'status': 'success'} even when webhook processing fails with an exception (line 107).

# Line 91-107
except Exception as e:
    logger.error(f"[WEBHOOK] Error processing webhook: {e}")
    # ...error logging...
    if event and hasattr(event, 'id'):
        await WebhookLock.mark_webhook_failed(event.id, error_message)

    return {'status': 'success', 'error': 'processed_with_errors', 'message': 'Webhook logged as failed internally'}

The endpoint in backend/core/billing/endpoints/webhooks.py directly returns this dict, so FastAPI sends a 200 response to Stripe.

Impact

• Stripe stops retrying failed webhooks — Stripe interprets any 2xx response as successful delivery and will not attempt redelivery (Stripe docs: retry behavior)
• Billing events are silently lost — failed checkout.session.completed, customer.subscription.updated, invoice.payment_succeeded, etc. events are never retried
• Users may pay but not receive their subscription — if the CheckoutHandler or SubscriptionHandler throws an exception, the payment went through on Stripe's side but Suna never processes it
• The failure IS logged internally and marked via WebhookLock.mark_webhook_failed(), but there is no automatic recovery path since Stripe won't retry

Expected behavior

When webhook processing fails, the handler should return a non-2xx status code (e.g., 500) so that Stripe retries the event delivery using its exponential backoff schedule (up to 3 days). The handler should still log the failure internally, but the HTTP response must signal failure to Stripe.

Suggested fix

Replace the return on line 107 with an HTTP 500 response:

except Exception as e:
    logger.error(f"[WEBHOOK] Error processing webhook: {e}")
    # ...existing error logging...
    if event and hasattr(event, 'id'):
        await WebhookLock.mark_webhook_failed(event.id, error_message)

    raise HTTPException(status_code=500, detail="Webhook processing failed")

This ensures Stripe retries the event while still preserving the internal failure tracking via WebhookLock.

[linear]

SUNA-1085