Cancel a delivery (status cancelled, reason manual): no further attempts. From pending, retrying or in_progress; a terminal row is 422. On an in_progress row the attempt in flight may still land as success, which wins over the cancel (result.in_flight_attempt_pending true: read the row again). expected_status is a compare-and-set guard (409 on a mismatch).

Contract:

• MCP tool cancel_webhook_log, registry package mcp.integrations/webhook_logs, mount integrations.webhooks.
• Operation action, response envelope action.
• Flags: dangerous: the MCP layer gates it behind a preview/commit token, and the effect cannot be undone through this API.