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This tutorial teaches you how to perform a basic token swap on Tempo’s native stablecoin DEX. You’ll use tempo-foundry CLI tools to interact directly with the protocol-level exchange.
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TLDR:
  • Swap stablecoins directly on Tempo’s enshrined DEX precompile
  • Use tempo-foundry’s cast with the --fee-token flag for gas payment
  • Pay fees in the same stablecoin you’re swapping—no native gas token required
  • Execute swaps in seconds with sub-second finality

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Prerequisites

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Tempo stablecoin exchange overview

Tempo features an enshrined DEX—a precompiled contract built into the protocol at a fixed address. You interact with it directly using the cast command from tempo-foundry.

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Key addresses

ContractAddress
Stablecoin Exchange0xDEc0000000000000000000000000000000000000
pathUSD (quote token)0x20C0000000000000000000000000000000000000
AlphaUSD0x20C0000000000000000000000000000000000001
BetaUSD0x20C0000000000000000000000000000000000002
ThetaUSD0x20C0000000000000000000000000000000000003

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Testnet configuration

ParameterValue
Network nameTempo Testnet (Andantino)
Chain ID42429
RPC URLhttps://rpc.testnet.tempo.xyz
Explorerexplore.tempo.xyz

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Step 1. Install tempo-foundry

Tempo-foundry is a Foundry fork with Tempo-specific features, including the --fee-token flag for paying gas in stablecoins. 
foundryup -n tempo
Verify the installation: 
cast --version
You should see output containing tempo in the version string.

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Step 2. Fund your wallet

Get testnet stablecoins using the faucet RPC method: 
cast rpc tempo_fundAddress YOUR_ADDRESS --rpc-url https://rpc.testnet.tempo.xyz
Check your balance: 
cast call 0x20C0000000000000000000000000000000000001 \
  "balanceOf(address)(uint256)" \
  YOUR_ADDRESS \
  --rpc-url https://rpc.testnet.tempo.xyz
The faucet provides AlphaUSD tokens. All testnet stablecoins use 6 decimals, so 100000000 equals $100.

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Step 3. Get a swap quote

Before swapping, check the expected output. The DEX uses uint128 for amounts: 
cast call 0xDEc0000000000000000000000000000000000000 \
  "quoteSwapExactAmountIn(address,address,uint128)(uint128)" \
  0x20C0000000000000000000000000000000000001 \
  0x20C0000000000000000000000000000000000002 \
  100000000 \
  --rpc-url https://rpc.testnet.tempo.xyz
This quotes swapping 100 AlphaUSD for BetaUSD. Expected output: 100000000 (100 BetaUSD at 1:1 rate).

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Step 4. Approve the DEX

Set your private key as an environment variable: 
export PRIVATE_KEY=your_private_key_here
Approve the DEX to spend your tokens: 
cast send 0x20C0000000000000000000000000000000000001 \
  "approve(address,uint256)" \
  0xDEc0000000000000000000000000000000000000 \
  100000000 \
  --rpc-url https://rpc.testnet.tempo.xyz \
  --private-key $PRIVATE_KEY \
  --fee-token 0x20C0000000000000000000000000000000000001
The --fee-token flag specifies which TIP-20 token to use for gas payment. Here we’re paying gas in AlphaUSD—the same token we’re approving.

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Step 5. Execute the swap

Swap 100 AlphaUSD for BetaUSD with 1% slippage tolerance: 
cast send 0xDEc0000000000000000000000000000000000000 \
  "swapExactAmountIn(address,address,uint128,uint128)(uint128)" \
  0x20C0000000000000000000000000000000000001 \
  0x20C0000000000000000000000000000000000002 \
  100000000 \
  99000000 \
  --rpc-url https://rpc.testnet.tempo.xyz \
  --private-key $PRIVATE_KEY \
  --fee-token 0x20C0000000000000000000000000000000000001
The parameters are:
  • tokenIn — AlphaUSD address
  • tokenOut — BetaUSD address
  • amountIn — 100 tokens (100000000 with 6 decimals)
  • minAmountOut — minimum 99 tokens (1% slippage protection)

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Step 6. Verify the swap

Check your new BetaUSD balance: 
cast call 0x20C0000000000000000000000000000000000002 \
  "balanceOf(address)(uint256)" \
  YOUR_ADDRESS \
  --rpc-url https://rpc.testnet.tempo.xyz

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DEX interface reference

The stablecoin exchange provides these key functions: 
// Swap exact input for variable output
function swapExactAmountIn(
    address tokenIn,
    address tokenOut,
    uint128 amountIn,
    uint128 minAmountOut
) external returns (uint128 amountOut);

// Swap variable input for exact output
function swapExactAmountOut(
    address tokenIn,
    address tokenOut,
    uint128 amountOut,
    uint128 maxAmountIn
) external returns (uint128 amountIn);

// Quote functions (view, no gas)
function quoteSwapExactAmountIn(address tokenIn, address tokenOut, uint128 amountIn)
    external view returns (uint128 amountOut);

function quoteSwapExactAmountOut(address tokenIn, address tokenOut, uint128 amountOut)
    external view returns (uint128 amountIn);
The interface uses uint128 for amounts, not uint256. This is important when building Solidity contracts that interact with the DEX.

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How routing works

Each stablecoin has pathUSD as its quote token. When swapping AlphaUSD → BetaUSD, the DEX routes automatically:
  1. AlphaUSD → pathUSD
  2. pathUSD → BetaUSD
Both orderbooks need liquidity for the swap to succeed. The quote functions account for this routing when calculating output amounts.

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Slippage protection

Always set slippage bounds to protect against price movement:
  • minAmountOut — minimum tokens to receive (for exact input swaps)
  • maxAmountIn — maximum tokens to spend (for exact output swaps)
For stablecoin pairs, 0.5-1% is typical since prices are pegged.

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Fee payment

Tempo has no native gas token. Use --fee-token with any TIP-20 stablecoin to pay transaction fees. The Fee AMM converts your payment to the validator’s preferred token automatically.

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Integrating from Solidity

If you’re building a smart contract that needs to swap, import the interface from tempo-std: 
forge install tempoxyz/tempo-std

import {IStablecoinExchange} from "tempo-std/interfaces/IStablecoinExchange.sol";

IStablecoinExchange constant DEX = IStablecoinExchange(0xDEc0000000000000000000000000000000000000);

// Approve first, then:
uint128 amountOut = DEX.swapExactAmountIn(tokenIn, tokenOut, amountIn, minAmountOut);

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Troubleshooting

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Quote returns zero or fails

The orderbook may lack liquidity for the requested pair or amount. Try:
  • A smaller swap amount
  • Checking if orders exist for this token pair on the explorer

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Swap reverts

Common causes:
  • Insufficient token approval for the DEX
  • Slippage tolerance too tight for current liquidity
  • No liquidity in one leg of the route (tokenIn → pathUSD or pathUSD → tokenOut)

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Transaction fails with gas error

Ensure you’re using the --fee-token flag with a valid TIP-20 token address. Tempo requires stablecoin gas payment.

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Next steps

Now that you can execute basic swaps:
  • Build a swap aggregator that finds optimal routes
  • Monitor orderbook state with dex_getOrderbooks RPC method
  • Create limit orders by providing liquidity to the orderbook

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See also