Inventory adjusted (Snapcaster → Platform)

Sent when an Order commits units on Snapcaster: one `inventory.adjusted` event per Order, carrying a signed per-sku `delta` for every line, so the Platform moves its on-hand with one handler (`on_hand += delta`). Each event carries `seller_id` so the Platform can route it to the right store. Signing, verification, and delivery semantics are identical to `order.created` (see https://developers.snapcaster.ca/guide/webhook-signing); only the `data` body differs. Dedup on `event_id`: delivery is at-least-once, and an undeduped `on_hand += delta` double-applies on a retry. **Ack = durably applied**: return 2xx only after the stock change is durably written (or durably enqueued). Snapcaster releases its Committed hold on your 2xx; if you cannot apply the delta, return non-2xx so it retries. Fields are tagged STABLE / PROVISIONAL; treat the payload as open and ignore unknown fields.

Delivery payload

The signed `inventory.adjusted` event.

{
  "event_id": "evt_sandbox_01K4A91J43MTZ8C2E7P5X6Q9NV",
  "type": "inventory.adjusted",
  "created_at": "2026-09-04T18:42:18.000Z",
  "data": {
    "seller_id": 42,
    "lines": [
      {
        "sku_id": 427286,
        "external_ref": "platform-listing-1042",
        "delta": -1
      }
    ],
    "reason": "sale",
    "order_ref": "ord_sandbox_01K4A8Y6D4QJH2N3P5R7S9T0VW"
  },
  "api_version": "2026-07"
}

Signature headers

Field	In	Type	Constraints	Meaning	Example
`X-Snapcaster-Timestamp`required	header	string	None	Unix seconds when the request was signed; reject if outside a ±5 minute window.	`string` (generated)
`X-Snapcaster-Signature`required	header	string	None	`sha256=` + lowercase hex of HMAC_SHA256(signingSecret, timestamp ‖ raw request body).	`string` (generated)

Envelope fields

Field	Type	Constraints	Meaning	Example
`event_id`required	string	None	Globally unique, stable across retries; the idempotency/dedup key (STABLE).	`evt_sandbox_01K4A91J43MTZ8C2E7P5X6Q9NV`
`type`required	string	allowed values: inventory.adjusted	Event discriminator; future inventory events reuse this envelope (STABLE).	`inventory.adjusted`
`created_at`required	string	None	ISO-8601 UTC instant the event was generated; unchanged across retries (STABLE).	`2026-09-04T18:42:18.000Z`
`data`required	object	None	The operation or event payload.	`{ "seller_id": 42, "lines": [ { "sku_id": 427286, "external_ref": "platform-listing-1042", "delta": -1 } ], "reason": "sale", "order_ref": "ord_sandbox_01K4A8Y6D4QJH2N3P5R7S9T0VW" }`
`api_version`required	string	allowed values: 2026-07	The dated partner API version this payload was serialized at: the version frozen when the delivery was enqueued (never the live pin), so every retry carries the same value and byte-identical bytes. Added additively per the tolerant-reader rule; see https://developers.snapcaster.ca/guide/api-versioning (STABLE).	`2026-07`

Receiver response

200 - Receiver acked: the delta is durably applied (or durably enqueued to apply), not merely received. Snapcaster releases the matching Committed hold against this acknowledgement.