> ## Documentation Index
> Fetch the complete documentation index at: https://docs.apistable.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Task webhooks

> Receive terminal task notifications.

> Operations are enabled individually by server configuration. Disabled operations return 503 without a task. Music credit deduction is currently disabled.

## Terminal notification contract

Successful song callbacks send the SongResult object directly, matching the complete object in query data.result. Other terminal callbacks use the task response envelope; result is object/null. Delivery retries never create another generation task.

The design places event ID, timestamp and HMAC-SHA256 signature in X-APIstable-\* headers. The signer must cover timestamp + "." + raw body. Receivers return 2xx quickly, deduplicate events, and query tasks if delivery is missed. Delivery errors never trigger generation or another charge. Outbound delivery pins a validated public IP and rejects redirects. Retrieve the account signing secret from GET /api/v1/webhooks/secret.


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