Claude Fable 5.1 & GPT-6 Astra packages are live

webhooks

API

Sending and receiving webhooks reliably — HMAC signatures, replay protection, at-least-once delivery, retries with backoff, and idempotent consumers.

Choose your model

Available for 11 model families. The engineering substance is the same in each; the structure, checklist phrasing and constraint ordering are tuned per family.