---
title: "Register approval webhook callback"
method: POST
path: "/api/v1/approvals/{id}/callback"
tags: ["Approval Queue"]
---

# Register approval webhook callback

`POST /api/v1/approvals/{id}/callback`

Register a one-shot callback URL for a specific approval request. When resolved, AgentChain POSTs the result with dual-signature headers: `x-agentchain-signature` (HMAC-SHA256 for web2 verification) and `x-agentchain-eip712-sig` (EIP-712 for crypto-native verification). The callback fires once and is then deleted. Primary use case: Trigger.dev `wait.forToken()` integration for zero-cost checkpoint-resume approval flows.

## Path parameters

- `id` string, required

## Request body

- object
  - `callbackUrl` string, uri, required — URL to receive the webhook POST when the approval is resolved

## Response `201`

Callback registered

- object
  - `registered` boolean
  - `approvalId` string

## Other responses

- `403` — Not your approval request
- `404` — Approval request not found

---

[API](https://skmtc.net/humbleaf/apis/agentchain-prior-api.md) · [All operations](https://skmtc.net/humbleaf/apis/agentchain-prior-api/llms.txt) · [OpenAPI document](https://skmtc-service-staging.skmtc.workers.dev/v1/apis/humbleaf/agentchain-prior-api/versions/33dd194c5572/schema)