POST /v1/responses, POST /v1/chat/completions, or POST /v1/messages, you can provide a completion webhook in request metadata. When processing finishes, Sail will POST the full response payload to your URL so you can process it without polling.
Enabling a completion webhook
Include acompletion_webhook URL in the metadata object of your create request. The URL must be http or https.
metadata.completion_webhook is omitted or invalid, no webhook request is sent. The create call and the response itself are unchanged; webhooks are optional and best-effort.
For Chat Completions and Anthropic Messages, pass the same metadata keys (completion_webhook, webhook_token) on the request body.
Webhook payload
Sail sends a POST request to your URL with:- Content-Type:
application/json - Body: The same general JSON object returned by
GET /v1/responses/{response_id}. Webhook payloads can omitmetadata.supercached_input_tokensandmetadata.supercache_write_input_tokens.
status: "completed" or
status: "incomplete". An incomplete payload is a successful webhook delivery,
not a webhook error. Its body preserves usage, incomplete_details, and any
partial output. Process that payload once and do not keep polling the response
for another status.
Securing webhooks with a token
To verify that incoming requests are from Sail, setwebhook_token in the metadata. Sail will send the value of webhook_token as a Bearer token in the Authorization header of the webhook POST.
Authorization: Bearer your-secret-token and reject requests that don’t match.
Delivery behavior
- Duplicates: Sail may occasionally deliver the same webhook more than once. Log the response
idfrom the webhook body and ignore events you have already processed. - Retries: Sail retries failed deliveries (a non-2xx status or a network error) in rounds. A round makes up to 3 attempts back to back within a 30-second budget, and failed rounds are repeated with increasing delays of up to a few minutes, for at most 20 rounds. A persistently failing endpoint can receive up to 60 requests for one response. Respond with a 2xx status as soon as you have accepted the payload so that Sail stops retrying.
- Best-effort: Webhook failures are logged but do not affect the response or the API. The response remains available via
GET /v1/responses/{response_id}even if the webhook never succeeds.
Full example
Here’s a full, end-to-end example using ngrok: 1. Start a local webhook listener that prints the payload and returns 200:https://xxxx.ngrok-free.app forwarding URL from the output.
3. In a third terminal, create a response with the webhook: