Gas Quotes

Overview

Every Cashmere transfer needs a fee quote signed by the Gas API: the contracts check the signature before they burn any USDC. A quote covers one route, fee mode and CCTP version, and expires about 100 seconds after it is issued.

Source chain	Endpoint
EVM chains	`GET /getEcdsaSig_native`
Solana, Aptos, Sui	`GET /getEd25519Sig_native`

`GET /getEcdsaSig_native`

An ECDSA quote for the EVM contracts: transferV2 and transferV2WithPermit, or the V1 transfer and transferWithPermit.

GET https://gas.cashmere.exchange/getEcdsaSig_native

Query Parameters

Name	Type	Required	Description
`localDomain`	number	Yes	Source CCTP domain (Ethereum `0`, Arbitrum `3`, Base `6`…)
`destinationDomain`	number	Yes	Destination CCTP domain
`isV2`	boolean	Yes	`true` for all new integrations (`transferV2`). `false` signs the V1 `transfer`, which Circle stops accepting on 1 December 2026
`isNative`	boolean	Yes	`true` to pay the fee in the source chain’s gas token, `false` to take it from the USDC. Without it the API answers 500

Example

curl "https://gas.cashmere.exchange/getEcdsaSig_native?localDomain=0&destinationDomain=3&isV2=true&isNative=false"

{
  "fee": "190000",
  "deadline": "1793034101",
  "signature": "0x8b6a…1b",
  "isNative": false,
  "cctpVersion": 2
}

Response Fields

Field	Description
`fee`	Cashmere’s fee, as a string: USDC base units with `isNative=false`, wei with `isNative=true`. It covers the destination mint, so it depends mostly on the destination chain
`deadline`	Unix seconds, about 100 seconds after the quote. The contract reverts after it
`signature`	65-byte ECDSA signature over `keccak256(abi.encodePacked(uint32 localDomain, uint32 destinationDomain, uint128 fee, uint64 deadline, bool isNative, uint8 cctpVersion))`, with no `\x19Ethereum Signed Message` prefix
`isNative`	The fee mode the quote was signed for
`cctpVersion`	`2` for `transferV2`, `1` for `transfer`

Gas drop is not offered: pass gasDropAmount: 0. With isNative=true, send at least fee as the transaction’s value (the contract refunds any excess); otherwise the contract takes the fee out of amount.

`GET /getEd25519Sig_native`

An Ed25519 quote for the Solana program and the Aptos and Sui modules.

GET https://gas.cashmere.exchange/getEd25519Sig_native

Query Parameters

Name	Type	Required	Description
`localDomain`	number	Yes	`5` Solana, `8` Sui, `9` Aptos
`destinationDomain`	number	Yes	Destination CCTP domain
`isNative`	boolean	Yes	`true` to pay in SOL, SUI or APT, `false` to take the fee from the USDC
`version`	number	For V2	`2` for the V2 entry points (`transfer_v2`, `transfer_v2_outer`, `prepare_deposit_for_burn_v2`), `1` for Solana V1. Leave it out only for the V1 Aptos and Sui calls

Example

curl "https://gas.cashmere.exchange/getEd25519Sig_native?localDomain=5&destinationDomain=0&isNative=false&version=2"

{
  "signature": "0x6c80…d4",
  "message": "0x020500000000000000ab981600000000007587df6a0000000000",
  "publicKey": "0x93ab…af",
  "destinationDomain": "0",
  "fee": "1480875",
  "deadline": "1793034101",
  "isNative": false,
  "version": 2
}

Response Fields

Field	Description
`signature`	64-byte Ed25519 signature, hex
`message`	The signed bytes, hex (see Message Layout)
`publicKey`	The Gas API’s Ed25519 key, which the contracts store
`destinationDomain`	The requested destination, as a string
`fee`	Cashmere’s fee, as a string: USDC base units with `isNative=false`; lamports (Solana), octas (Aptos) or MIST (Sui) with `isNative=true`
`deadline`	Unix seconds, about 100 seconds after the quote
`isNative`	The fee mode the quote was signed for
`version`	The requested version; absent if you left it out

Message Layout

Little-endian, 26 bytes (25 without version):

version (u8), only if you passed version
localDomain (u32)
destinationDomain (u32)
fee (u64)
deadline (u64)
isNative (bool)

The Solana program reads these bytes from the Ed25519Program instruction placed before the transfer. The Aptos and Sui modules rebuild them as the BCS encoding of TransferParamsV2 and verify the signature you pass. See Signed Payloads.

Token Pricing

GET https://gas.cashmere.exchange/tokenPrices

The USD price of each chain’s gas token, as decimal strings keyed by chain name:

{
  "ethereum": "2315.28",
  "solana": "100.99",
  "aptos": "0.692416",
  "sui": "0.91108"
}

WebSocket Updates

wss://gas.cashmere.exchange/subscribe

The socket sends the current fees and token prices as soon as you connect:

{ "type": "fees", "data": { <sourceChain>: { fee: { <destinationChain>: { native, usd } }, gas: { native, usd } } } }
{ "type": "tokenPrices", "data": { <chain>: "<USD price>" } }

Keys are chain names, not domain IDs. native is in the source chain’s smallest native unit, and usd in USDC base units ("190000" is 0.19 USDC).

const socket = new WebSocket('wss://gas.cashmere.exchange/subscribe');

socket.onmessage = (event) => {
  const { type, data } = JSON.parse(event.data);
  if (type === 'fees') {
    console.log('Base → Arbitrum fee:', Number(data.base.fee.arbitrum.usd) / 1e6, 'USDC');
  }
};

Use the socket for display only: a transfer still needs a signed quote from the REST endpoints.

Failure Modes

HTTP Status	Body	Meaning
`500`	`{"error":"Internal Server Error"}`	Bad input (a missing `isNative`, an unknown domain, `TRUE` instead of `true`), or the route can’t be priced right now

The Gas API doesn’t answer 400. Check the parameters first, then retry with backoff, and never sign with an expired quote.

Welcome

Overview

Products

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Developer Resources

API Reference

Overview

`GET /getEcdsaSig_native`

Query Parameters

Example

Response Fields

`GET /getEd25519Sig_native`

Query Parameters

Example

Response Fields

Message Layout

Token Pricing

WebSocket Updates

Failure Modes

​Overview

​GET /getEcdsaSig_native

​Query Parameters

​Example

​Response Fields

​GET /getEd25519Sig_native

​Query Parameters

​Example

​Response Fields

​Message Layout

​Token Pricing

​WebSocket Updates

​Failure Modes

Overview

`GET /getEcdsaSig_native`

Query Parameters

Example

Response Fields

`GET /getEd25519Sig_native`

Query Parameters

Example

Response Fields

Message Layout

Token Pricing

WebSocket Updates

Failure Modes