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

# Register approval webhook 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.



## OpenAPI

````yaml POST /api/v1/approvals/{id}/callback
openapi: 3.0.0
info:
  title: AgentChain & PRIOR API
  description: The centralized gateway for the decentralized compute network.
  version: '1.0'
  contact: {}
servers:
  - url: https://api.agentchain.xyz
    description: Production
security: []
tags: []
paths:
  /api/v1/approvals/{id}/callback:
    post:
      tags:
        - Approval Queue
      summary: Register approval webhook callback
      description: >-
        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.
      operationId: ApprovalController_registerCallback
      parameters:
        - name: id
          required: true
          in: path
          description: Approval request ID
          schema:
            type: string
      requestBody:
        required: true
        description: Callback registration payload
        content:
          application/json:
            schema:
              type: object
              required:
                - callbackUrl
              properties:
                callbackUrl:
                  type: string
                  format: uri
                  description: >-
                    URL to receive the webhook POST when the approval is
                    resolved
                  example: https://api.trigger.dev/wait/token/abc123
      responses:
        '201':
          description: Callback registered
          content:
            application/json:
              schema:
                type: object
                properties:
                  registered:
                    type: boolean
                    example: true
                  approvalId:
                    type: string
        '403':
          description: Not your approval request
        '404':
          description: Approval request not found
      security:
        - x-api-key: []
        - bearer: []
components:
  securitySchemes:
    x-api-key:
      type: apiKey
      in: header
      name: x-api-key
    bearer:
      scheme: bearer
      bearerFormat: JWT
      type: http

````