generated: '2026-08-06'
method: searched
source: https://api.arkestro.com/api-docs/v2/openapi.yaml
spec_type: Webhooks
asyncapi: null
asyncapi_note: >-
  Arkestro publishes no AsyncAPI document and no top-level OpenAPI 3.1 `webhooks` object.
  The entire outbound event contract is carried in prose, as an `x-traitTag` tag named
  "Webhooks" inside the REST OpenAPI. That is a real, detailed, machine-fetchable webhook
  specification — signing, replay window, retry schedule and delivery semantics are all
  precisely stated — but the event catalog itself (which events fire, and their payload
  schemas) is NOT in the public spec, so no channel or message schema can be recorded here
  without fabricating it.
transport: HTTP POST to a subscriber-supplied endpoint
security:
  signing:
    algorithm: HMAC-SHA256
    header: X-Arkestro-Signature
    format: sha256=<lowercase hex digest>
    multiple_signatures: >-
      One or more signatures, comma-joined with no whitespace. Multiple values appear during
      secret rotation, so verifiers must accept a match against any candidate.
    signed_payload: '{X-Arkestro-Timestamp}.{raw_request_body}'
    raw_body_required: true
    comparison: constant-time
  replay_protection:
    header: X-Arkestro-Timestamp
    format: Unix epoch seconds, as a string
    in_signed_payload: true
    recommended_tolerance_seconds: 300
  verification_examples_published:
  - node.js
  - python
  - ruby
delivery:
  idempotency:
    header: X-Arkestro-Idempotency-Key
    value: UUID identifying the delivery event
    stable_across_retries: true
    in_signed_payload: false
    purpose: >-
      Consumer-side deduplication of retried deliveries. Generated once when the event fires
      and constant across every retry attempt of that delivery, unlike `request_id` in the
      body which changes on every attempt.
    scope: inbound-webhook-delivery-only
    not_request_idempotency: >-
      IMPORTANT: this is delivery dedupe for Arkestro's outbound webhooks. It is NOT an
      idempotency-key contract for the REST API's own POST/PATCH writes, which have none.
  acknowledgement:
    success: any 2xx (200, 201, 202, 204 treated identically); response body ignored
    timeout_seconds: 10
    guidance: enqueue slow processing and return 2xx immediately
  retry:
    retried_on:
    - '429'
    - 5xx
    - transport errors (timeouts, connection failures)
    not_retried_on:
    - 4xx except 429 (treated as permanent failure, delivery discarded)
    max_attempts: 10
    strategy: exponential backoff
    final_attempt_after: approximately 4-5 hours after the initial attempt
    on_exhaustion: delivery permanently abandoned
events:
  catalog_published: false
  note: >-
    No event-type list, no payload schemas and no subscription-management endpoints appear
    in the public OpenAPI. Subscription is presumably configured in the tenant application
    behind app.arkestro.com. Nothing is asserted here about which events exist.
payload_fields_referenced:
- field: request_id
  location: body
  note: changes on every delivery attempt (contrast with X-Arkestro-Idempotency-Key)
gaps:
- No AsyncAPI document, so the event surface is not machine-readable as an event contract.
- No published event-type catalog or payload schemas.
- No webhook subscription/management operations in the public REST API.
x-evidence:
- url: https://api.arkestro.com/api-docs/v2/openapi.yaml
  http_status: 200
  fetched: '2026-08-06'
  locator: 'tags[] entry name="Webhooks", x-traitTag: true'