Bridge limits and fees

This guide shows you how to read the bridge’s current limits and fees from the contracts, so your app never relies on a number that has changed.

Everything on this page uses testnet (chain 968). Get free test tokens from the faucet.

What you can read

Value	Where	Unit
Paused	Router `getBridgePause()`	`true` or `false`
Minimum fee	Router `getMinFee()`	Whole USDT
Minimum amount	Router `getMinAmountUsd()`	Whole USDT
Maximum amount	Router `getMaxAmountUsd()`	Whole USDT
Supported destinations	Bridge `getSupportedDestinationChains(srcChainId)`	Chain IDs
Fee per destination	Bridge `chainAndTokenFee(destChainId, resourceId)`	Basis points

The router’s Bridge() function returns the bridge contract’s address. The limits are in whole USDT, not base units. Convert them with parseUnits(value.toString(), 6) before comparing with an amount.

Steps

Set up the project

Use the bot-defi project from Wrap BOT. This script only reads, so it needs no key.

Write the script

bridge-limits.ts

import { createPublicClient, formatUnits, http, parseAbi } from "viem";
import { botChainTestnet } from "@uzolabs/sdk/chains";
import { botBridgeAbi, getAddresses, USDT_RESOURCE_ID } from "@uzolabs/sdk/contracts";

const publicClient = createPublicClient({ chain: botChainTestnet, transport: http() });
const { bridgeRouter } = getAddresses(botChainTestnet.id);
const bridgeAbi = parseAbi([
  "function getSupportedDestinationChains(uint256 srcChainId) view returns (uint256[])",
  "function chainAndTokenFee(uint256 destChainId, bytes32 resourceId) view returns (uint256)",
]);

const [bridge, paused, minFee, minUsd, maxUsd] = await Promise.all([
  publicClient.readContract({ address: bridgeRouter, abi: botBridgeAbi, functionName: "Bridge" }),
  publicClient.readContract({ address: bridgeRouter, abi: botBridgeAbi, functionName: "getBridgePause" }),
  publicClient.readContract({ address: bridgeRouter, abi: botBridgeAbi, functionName: "getMinFee" }),
  publicClient.readContract({ address: bridgeRouter, abi: botBridgeAbi, functionName: "getMinAmountUsd" }),
  publicClient.readContract({ address: bridgeRouter, abi: botBridgeAbi, functionName: "getMaxAmountUsd" }),
]);
const destinations = await publicClient.readContract({ address: bridge, abi: bridgeAbi, functionName: "getSupportedDestinationChains", args: [BigInt(botChainTestnet.id)] });

console.log(`Router ${bridgeRouter}, bridge ${bridge}`);
console.log(`Paused: ${paused}`);
console.log(`Min fee: ${minFee} USDT, min amount: ${minUsd} USDT, max amount: ${maxUsd} USDT`);
for (const dest of destinations) {
  const bps = await publicClient.readContract({ address: bridge, abi: bridgeAbi, functionName: "chainAndTokenFee", args: [dest, USDT_RESOURCE_ID] });
  console.log(`To chain ${dest}: fee ${bps} bps (${formatUnits(bps, 2)}%)`);
}

botBridgeAbi and USDT_RESOURCE_ID come from @uzolabs/sdk/contracts. The two bridge functions aren’t in that ABI, so the script declares them with parseAbi.

Run it

npx tsx bridge-limits.ts

Verify it worked

On testnet on 2026-10-02:

Output

Router 0x6239404Aa276ba68486E2Fa40E90CDd36ff8ec3A, bridge 0xB6Aa106b8FC187779F9cdD5590018C479A166e9a
Paused: false
Min fee: 1 USDT, min amount: 10 USDT, max amount: 50000 USDT
To chain 97: fee 10 bps (0.1%)
To chain 11155111: fee 10 bps (0.1%)
To chain 3448148188: fee 10 bps (0.1%)

To read mainnet, import botChain instead of botChainTestnet and use botChain in both places. The same day, mainnet returned the same fee and minimums, a maximum of 30150 USDT, and destinations 56, 1 and 728126428. Mainnet and testnet limits differ, so always read the network you’re sending on.

Work out the fee

The fee is the percentage or the minimum fee, whichever is larger, and comes out of the amount you send:

bridge-fee.ts

import { parseUnits } from "viem";

export function bridgeFee(amount: bigint, feeBps: bigint, minFeeUsdt: bigint): bigint {
  const percentFee = (amount * feeBps) / 10_000n;
  const minFee = parseUnits(minFeeUsdt.toString(), 6);
  return percentFee > minFee ? percentFee : minFee;
}

This matches real testnet transfers: a 1,000 USDT deposit delivered 999, a 500 USDT deposit delivered 499, and an 11 USDT deposit delivered 10, because 0.1% of 500 or 11 is below the 1 USDT minimum. BOT Chain’s fee docs describe the same rule for bridging out and say bridging in is free of bridge fees.

Check before every transfer

Stop if getBridgePause() is true.
Check the amount is between the minimum and maximum.
Check the destination is in the supported list.
Show the user the fee and the amount that will arrive.

Troubleshooting

The limits look 10^6 times too small

They’re whole USDT, not base units. 10 means 10 USDT.

chainAndTokenFee returns 0 or reverts

Call it on the bridge address from Bridge(), not on the router, and pass the USDT resource ID from Contract addresses.

Development environment

Deploy and verify

Frontend

DeFi

Bridge

Gasless transactions

AI agents

Data and indexing

Bridge limits and fees

What you can read

Steps

Verify it worked

Work out the fee

Check before every transfer

Troubleshooting

Next steps

Bridge USDT out

Track a transfer

​What you can read

​Steps

​Verify it worked

​Work out the fee

​Check before every transfer

​Troubleshooting

​Next steps

Bridge USDT out

Track a transfer

What you can read

Steps

Verify it worked

Work out the fee

Check before every transfer

Troubleshooting

Next steps