> ## Documentation Index
> Fetch the complete documentation index at: https://docs.eco.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Cross-stable RFQ

> Swap one stablecoin for another (USDC ↔ USDT, USDC ↔ USDG) across chains, with competitive solver pricing and atomic settlement.

A **cross-stable RFQ** is an intent where the input and output stablecoins differ, for example, paying USDC on Optimism and receiving USDT on Base. Solvers compete on pricing in real time; the user gets the best quote without manual route comparison.

## When to use

* Accepting payment in any major stablecoin and settling to one preferred currency
* Moving from a chain-native stable (e.g. USDbC) to the canonical version (e.g. USDC) on the destination
* Cross-chain stable-to-stable swaps that would otherwise require routing through a DEX

## How quoting works

1. Your app submits a candidate intent (with `source`, `destination`, input token, and desired output token) to the [Quotes API](/api-reference/introduction#quotes).
2. Eco fans the request out to all registered solvers in parallel.
3. The aggregator returns ranked quotes, best price first.
4. Your app picks a quote, populates `intent.reward.tokens` from it, and publishes.

Quotes specify the reward tokens the user must lock in the source vault. Settlement is conditional on solver-provided proof.

## Properties

* **Best execution by competition.** Multiple solvers, ranked offers, no monopoly LP.
* **Atomic.** The user signs once. Either the swap lands or the reward is refunded.
* **No DEX exposure.** Solvers source the destination stable however they like; the user holds no DEX risk.

## Example pairs

| Source (chain → token) | Destination (chain → token) |
| ---------------------- | --------------------------- |
| Optimism USDC          | Base USDT                   |
| Arbitrum USDT0         | Polygon USDC                |
| Base USDC              | Solana USDG                 |
| Ethereum USDC          | Optimism oUSDT              |

See [Supported chains & tokens](/resources/supported-chains-tokens) for the full matrix.