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Contract calls & approvals

From a web3 vault you can make arbitrary EVM contract calls and ERC-20 approvals. ZenVault signs them and (for the transfer path) broadcasts them; you supply gas and chainId, ZenVault owns the nonce.

Approve a spender​

POST /v1/transfers/approve
Idempotency-Key: <uuid>
{
  "srcAccountId": "8f1c...",
  "tokenAssetCanonical": "USDT_ETHEREUM",
  "spender": "0xdef1c0ded9bec7f1a1670819833240f027b25eff",
  "amount": "1000000",
  "evm": { "chainId": 1, "gasLimit": 60000,
           "maxFeePerGas": "30000000000", "maxPriorityFeePerGas": "1500000000" }
}

Call a contract​

POST /v1/transfers/contract-call
Idempotency-Key: <uuid>
{
  "srcAccountId": "8f1c...",
  "chainAssetCanonical": "ETH_ETHEREUM",
  "contractAddress": "0xdef1c0ded9bec7f1a1670819833240f027b25eff",
  "data": "0x38ed1739...",
  "value": "0",
  "evm": { "chainId": 1, "gasLimit": 220000,
           "maxFeePerGas": "30000000000", "maxPriorityFeePerGas": "1500000000" }
}
  • Supply one of gasPrice (legacy) or maxFeePerGas + maxPriorityFeePerGas (EIP-1559).
  • chainId and gasLimit are mandatory; nonce is server-assigned.

Get the signed bytes (self-broadcast paths)​

If you broadcast yourself (swap fills, atomic windows), poll for the raw signed transaction after creating the call:

GET /v1/transfers/{id}/signed-tx
→ { "signedTransaction": "0x02f86a01...", "txHash": "0xaa11...", "state": "broadcasting" }

signedTransaction is null while signing is in flight — poll every couple of seconds until it's a hex string, then submit it through your own RPC.

Time-sensitive swaps: pre-gas first​

A web3 vault must hold native gas before its swap can broadcast. If the vault is cold, the reactive top-up can take a minute — long enough to expire an RFQ quote. Call POST /v1/gas/ensure before you request the quote so the signed swap broadcasts immediately, inside the quote window.

:::note Raw signing is different If you need to sign a message or a fully self-managed transaction (your own nonce, your own broadcast), use raw signing instead — it has no amount/destination policy, so gate it yourself. :::