Idempotency

POST /gasless/submit is the only POST endpoint. It can be sent again without creating a second trade.

By trade hash

Every gasless trade has a tradeHash: the EIP-712 digest of trade.eip712, also returned as trade.hash by the quote.

Same `tradeHash` sent again	Answer
From the same app	`200` with the same body `{ tradeHash, type, zid }`
From another app	`400 TRADE_ALREADY_SUBMITTED`

A trade can be executed once: the Permit2 nonce inside the signature is spent by the trade.

Idempotency-Key header

The optional header Idempotency-Key adds request-level replay:

1 to 64 visible ASCII characters (^[\x21-\x7e]{1,64}$).
Kept for 24 hours per app.
Same key and same body: the stored answer is returned.
Same key and a different body: 400 IDEMPOTENCY_KEY_REUSED.

A good key is the tradeHash without its 0x prefix (64 hex characters), or your own order id.

curl -s https://api.qiguard.com/gasless/submit \
  -H "qg-api-key: $QG_API_KEY" -H "qg-version: v1" -H "content-type: application/json" \
  -H "Idempotency-Key: order-2026-10-24-0001" \
  --data @submit.json

GET requests

All other endpoints are GET and change nothing, so they can be repeated at any time.

This page as Markdown: idempotency.md. All pages for tools: llms.txt.