500 means 'retry me.' Everything else that isn't a duplicate should be 200.

A webhook ingest path should do exactly three things -- verify, persist, 2xx -- and the only case that should ever return 500 is the database write itself failing (D4).

This is one of the things Webhook Durability & Replay already handles. Receive webhooks without losing, duplicating or misordering them when the sender retries.

Buy for $1493 of 3 clean-room builds passed · full refund if it fails on your machine

Is this you?

Returning 4xx or 5xx for an event type the app doesn't handle yet is how Shopify deletes a subscription and how Svix disables an endpoint -- providers read repeated non-2xx as a broken integration, not a shrug. Conversely, doing real business logic inline before responding risks blowing past a provider's response budget (Shopify's is 5 seconds total, 1 second to connect) under any load spike.

Why this one is easy to get wrong

Returning an error status for "I don't recognize this event type" feels like honest, defensive coding -- surfacing the unknown case rather than silently accepting it. Nothing in a quick manual test reveals that the provider interprets that honesty as endpoint failure and starts disabling the very channel the code is trying to protect.

What you get instead

D4 pins the whole contract: an unknown provider path is 404 (nothing written); a missing or invalid signature is 401 (nothing written); a payload that verifies but fails to parse is still 200 with a dead row persisted (D5); a new or already-seen delivery is 200 either way; and 500 is reserved exclusively for the database write failing, since that's the one case a provider retrying actually helps. 200, specifically -- not 202 -- because 200 is the only code inside every one of the five providers' documented success bands.

Source: ARCHITECTURE.md D4 — checkable in the pack you receive

How you actually use this

You don’t install a library or wire up an SDK. Your own coding agent builds the code in your project, and you keep it — no runtime dependency on us.

Step 1
Download and unzip
You get a folder: the docs that tell an agent what to build, a starting skeleton, and the test suite that decides when it's done.
Step 2
Open it in Claude Code or Cursor
Point your coding agent at the folder. Nothing to install, no account with us, no API key.
Step 3
Paste one prompt
The pack contains the exact prompt. Paste it as your first message and leave it alone — it works through the build itself, choosing a cheaper or stronger model per task.
Step 4
Run ./verify.sh
One command. It prints a pass or fail for every check. Green means the build is done — the same script we ran to produce the receipt on this page.

Typical build: about 40 minutes of your agent working, mostly unattended. Then you integrate the working module into your app the way you would any code you’d written yourself.

Why you can believe this

3 of 3 runs passed

We ran this pack from an empty folder 3 times and published exactly what happened — every check, the model, the token cost, the wall time. Not a testimonial, and not our opinion: the same verify.sh you run yourself. Read the full receipt →

Buy for $149 14-day refund if verify.sh fails →