Receive and verify CircleCI outbound webhooks. Use when setting up a CircleCI webhook handler, debugging `circleci-signature` verification, or handling the `workflow-completed` and `job-completed` events CircleCI sends when a workflow or job reaches a terminal state. CircleCI signs the raw body with HMAC-SHA256 and sends a hex digest in a comma-separated versioned list (`v1=<hex>`) — only the latest version (`v1`) should ever be checked. Not Circle (circle.com, USDC/Circle Mint, ECDSA `X-Circle-Signature`) — unrelated company. Not CircleCI custom webhooks, which are inbound pipeline triggers going the other direction.