I keep finding the same Stripe webhook bugs in SaaS launches

Most early SaaS billing bugs are not in Stripe Checkout itself. They are in the glue around it:

trusting the success redirect instead of the signed webhook
parsing JSON before signature verification
missing idempotency for retry events
reflecting verifier errors from unauthenticated webhook routes
updating subscription state without a replay/audit trail
letting "Pro" access drift from the payment source of truth

Over the last few days I have been shipping small public fixes around exactly this class of problem.

Recent examples:

Morphix: Cloudflare Worker Stripe webhook with signature verification, Supabase subscription sync, and event idempotency ledger

https://github.com/yiyuanlee/morphix/pull/25
Open Mercato: hardened unauthenticated payment/shipping provider webhooks against raw verifier error reflection and missing rate limiting

https://github.com/open-mercato/open-mercato/pull/2680
Covenant: webhook signatures hardened against replay and secret rotation gaps

https://github.com/wienerlabs/covenant/pull/229
Volunteerflow: made a Stripe invoice.paid Founders Circle counter update transactional instead of partially committing user/counter state

https://github.com/ppppowers/volunteerflow-project/pull/49

The pattern is boring in the best possible way: payment systems should be boring.

The 48-hour version

For a small SaaS that is about to turn on paid plans, I can take a bounded payment assurance sprint:

inspect Checkout / webhook / subscription state flow
verify signed webhook handling and raw-body behavior
add idempotency around Stripe retry events
ensure subscription status and entitlement state have one source of truth
add a small regression test or smoke script
leave a deploy/runbook note so the next failure is diagnosable

Fixed scopes I am taking:

$2,000 / 48 hours: one payment path hardened and documented
$5,000 / 5 days: full launch pass across Checkout, webhook, subscription mirror, Pro gate, pricing page handoff, and smoke test

I am not dropping a checkout link into a blog post. If you have a live Stripe/Supabase/Cloudflare/Vercel billing path and want me to take the first sprint, reply with: