Sume Format webhook: verify the timestamp, register the final URL
Sume signs format.run.terminal with HMAC-SHA256, expects a response in 10 seconds, retries up to 10 times and does not follow redirects. Register the final URL.
Sume signs the format.run.terminal webhook with HMAC-SHA256 over <timestamp>.<raw_body>. Reject any delivery whose timestamp is outside your tolerance window; the docs call five minutes reasonable. Answer within 10 seconds, because slower responses count as a failed attempt, and register the final URL, because Sume does not follow redirects. Dedupe on request_id. Sources: Webhooks and Formats errors and spend, read 2026-10-06.
What are the delivery rules?
The rules that decide whether your endpoint works.
| Rule | Value |
|---|---|
| Signature header | x-sume-webhook-signature: sume-v1=<hex> |
| Timestamp header | x-sume-webhook-timestamp |
| Secret check | x-sume-webhook-secret-fingerprint |
| Response limit | 10 seconds |
| Attempts | Up to 10, backoff capped at one hour |
| Redirects | Not followed |
| Large receipt | payload is null when the receipt exceeds 1 MiB |
What if a delivery failed?
Read the receipt at result_url, correct the endpoint, and send POST /v1/format-runs/{id}/webhook/redeliver. During a secret rotation the signature header carries one sume-v1= entry per live secret, so accept the delivery when any entry matches. If nothing verifies, compare the fingerprint header with the one on the receipt.
Sources
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