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swap-integration

Stars42

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UpdatedMarch 23, 2026 at 11:57

Integrate PancakeSwap swaps into applications. Use when user says "integrate swaps", "pancakeswap", "smart router", "add swap functionality", "build a swap frontend", "create a swap script", "smart contract swap integration", "use Universal Router", or mentions swapping tokens via PancakeSwap.

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pancakeswap/pancakeswap-ai

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Software DevelopersComputer and Mathematical Occupations·SOC 15-1252

SKILL.md

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Swap Integration

Integrate PancakeSwap swaps into frontends, backends, and smart contracts.

Quick Decision Guide

Building...	Use This Method
Quick quote or prototype	PancakeSwap Routing API (Method 1)
Frontend with React/Next.js	Smart Router SDK + Universal Router (Method 2)
Backend script or trading bot	Smart Router SDK + Universal Router (Method 2)
Simple V2 swap, smart contract	Direct V2 Router contract calls (Method 3)
Need exact Universal Router encoding	Universal Router SDK directly (Method 2)
Swap through Infinity (v4) CL or Bin pools	Routing API (Method 1) or Smart Router SDK with Infinity pool types (Method 2)

Protocol Types

Protocol	Description	Fee Tiers (bps)	Chains
V2	Classic AMM (xy=k), constant product formula	25 (0.25%)	BSC only
V3	Concentrated liquidity (Uniswap V3-compatible)	1, 5, 25, 100 (0.01–1%)	All chains
StableSwap	Low-slippage for correlated/pegged assets	1, 4 (0.01–0.04%)	BSC only
Infinity CL	Concentrated liquidity in the v4 singleton PoolManager; supports hooks for custom logic	Same tiers as V3	BSC, Base
Infinity Bin	Fixed-price-bin liquidity (similar to Trader Joe v2); tight ranges, predictable bin-level prices	Configurable	BSC, Base
Mixed	Split route across any combination of the above protocols	N/A (composite)	BSC primarily

Supported Chains

Chain	Chain ID	V2	V3	StableSwap	Infinity CL	Infinity Bin	RPC
BNB Smart Chain	56	✅	✅	✅	✅	✅	`https://bsc-dataseed1.binance.org`
BNB Smart Chain Testnet	97	✅	❌	❌	❌	❌	`https://bsc-testnet-rpc.publicnode.com or https://bsc-testnet.drpc.org`
Ethereum	1	❌	✅	❌	❌	❌	`https://cloudflare-eth.com`
Arbitrum One	42161	❌	✅	❌	❌	❌	`https://arb1.arbitrum.io/rpc`
Base	8453	❌	✅	❌	✅	✅	`https://mainnet.base.org`
Polygon	137	❌	✅	❌	❌	❌	`https://polygon-rpc.com`
zkSync Era	324	❌	✅	❌	❌	❌	`https://mainnet.era.zksync.io`
Linea	59144	❌	✅	❌	❌	❌	`https://rpc.linea.build`
opBNB	204	❌	✅	❌	❌	❌	`https://opbnb-mainnet-rpc.bnbchain.org`

For testing: Use BSC Testnet (chain ID 97). Get free testnet BNB from https://testnet.bnbchain.org/faucet-smart. The Smart Router SDK does not index testnet pools — use Method 3 (Direct V2 Router) on testnet.

Key Token Addresses

BSC Mainnet (Chain ID: 56)

Token	Address
WBNB	`0xbb4CdB9CBd36B01bD1cBaEBF2De08d9173bc095c`
BUSD	`0xe9e7CEA3DedcA5984780Bafc599bD69ADd087D56`
USDT	`0x55d398326f99059fF775485246999027B3197955`
USDC	`0x8AC76a51cc950d9822D68b83fE1Ad97B32Cd580d`
CAKE	`0x0E09FaBB73Bd3Ade0a17ECC321fD13a19e81cE82`
ETH	`0x2170Ed0880ac9A755fd29B2688956BD959F933F8`
BTCB	`0x7130d2A12B9BCbFAe4f2634d864A1Ee1Ce3Ead9c`

BSC Testnet (Chain ID: 97)

Token	Address	Notes
WBNB	`0xae13d989daC2f0dEbFf460aC112a837C89BAa7cd`
CAKE	`0xFa60D973f7642b748046464E165A65B7323b0C73`
BUSD	`0xeD24FC36d5Ee211Ea25A80239Fb8C4Cfd80f12Ee`
V2Router	`0x9Ac64Cc6e4415144C455BD8E4837Fea55603e5c3`	PancakeSwap testnet

Universal Router Addresses

Chain	Chain ID	Universal Router Address
BNB Smart Chain	56	`0x3fC91A3afd70395Cd496C647d5a6CC9D4B2b7FAD`
Ethereum	1	`0x3fC91A3afd70395Cd496C647d5a6CC9D4B2b7FAD`
Arbitrum	42161	`0x3fC91A3afd70395Cd496C647d5a6CC9D4B2b7FAD`
Base	8453	`0x198EF79F1F515F02dFE9e3115eD9fC07183f02fC`
Polygon	137	`0x3fC91A3afd70395Cd496C647d5a6CC9D4B2b7FAD`
zkSync Era	324	`0x3fC91A3afd70395Cd496C647d5a6CC9D4B2b7FAD`
Linea	59144	`0x3fC91A3afd70395Cd496C647d5a6CC9D4B2b7FAD`
opBNB	204	`0x3fC91A3afd70395Cd496C647d5a6CC9D4B2b7FAD`

Method 1: PancakeSwap Routing API (Simplest)

Best for: Quick quotes, prototypes, and situations where you don't want to manage on-chain pool data yourself. No SDK installation required.

Base URL: https://router.pancakeswap.finance/v0/quote

Get a Quote

# Exact input: 1 BNB → CAKE on BSC
curl -s "https://router.pancakeswap.finance/v0/quote?\
tokenInAddress=BNB\
&tokenInChainId=56\
&tokenOutAddress=0x0E09FaBB73Bd3Ade0a17ECC321fD13a19e81cE82\
&tokenOutChainId=56\
&amount=1000000000000000000\
&type=exactIn\
&maxHops=3\
&maxSplits=4" | jq '{
  amountOut: .trade.outputAmount,
  priceImpact: .trade.priceImpact,
  route: [.trade.routes[].type]
}'

API Parameters

Parameter	Type	Description
`tokenInAddress`	string	Input token address or `"BNB"` / `"ETH"` for native
`tokenInChainId`	number	Input chain ID
`tokenOutAddress`	string	Output token address
`tokenOutChainId`	number	Output chain ID
`amount`	string	Amount in raw units (wei for 18-decimal tokens)
`type`	string	`"exactIn"` or `"exactOut"`
`maxHops`	number	Max hops per route (default: 3)
`maxSplits`	number	Max route splits (default: 4)

Infinity (v4) support: The Routing API automatically considers Infinity CL and Infinity Bin pools on BSC and Base alongside V2/V3/StableSwap. No extra parameters are needed — the router selects the best route across all pool types.

TypeScript Fetch Example

interface PancakeRouteQuote {
  trade: {
    inputAmount: string
    outputAmount: string
    priceImpact: string
    routes: Array<{ type: 'V2' | 'V3' | 'STABLE' | 'MIXED'; pools: unknown[] }>
    blockNumber: number
  }
}

async function getQuote(params: {
  tokenIn: string
  tokenOut: string
  chainId: number
  amount: bigint
  type: 'exactIn' | 'exactOut'
}): Promise<PancakeRouteQuote> {
  const url = new URL('https://router.pancakeswap.finance/v0/quote')
  url.searchParams.set('tokenInAddress', params.tokenIn)
  url.searchParams.set('tokenInChainId', String(params.chainId))
  url.searchParams.set('tokenOutAddress', params.tokenOut)
  url.searchParams.set('tokenOutChainId', String(params.chainId))
  url.searchParams.set('amount', String(params.amount))
  url.searchParams.set('type', params.type)
  url.searchParams.set('maxHops', '3')
  url.searchParams.set('maxSplits', '4')

  const res = await fetch(url.toString())
  if (!res.ok) throw new Error(`Routing API error: ${res.status} ${await res.text()}`)
  return res.json()
}

// Usage
const quote = await getQuote({
  tokenIn: 'BNB',
  tokenOut: '0x0E09FaBB73Bd3Ade0a17ECC321fD13a19e81cE82', // CAKE
  chainId: 56,
  amount: BigInt('1000000000000000000'), // 1 BNB
  type: 'exactIn',
})

console.log('Output:', quote.trade.outputAmount, 'CAKE (raw)')
console.log('Price impact:', quote.trade.priceImpact, '%')

Quote freshness: Re-fetch if the quote is more than ~15 seconds old before broadcasting. Stale quotes frequently fail with INSUFFICIENT_OUTPUT_AMOUNT.

Method 2: Smart Router SDK + Universal Router SDK

Best for: Frontends and backends that need full programmatic control over routing and transaction encoding. Operates entirely on-chain — no external API dependency.

Installation

npm install @pancakeswap/smart-router @pancakeswap/sdk @pancakeswap/v3-sdk @pancakeswap/universal-router-sdk viem@2.37.13

Package Roles

Package	Role
`@pancakeswap/smart-router`	Pool fetching + best route finding
`@pancakeswap/sdk`	Core types: Token, CurrencyAmount, Percent, etc.
`@pancakeswap/v3-sdk`	V3-specific types: FeeAmount, pool encoding
`@pancakeswap/universal-router-sdk`	Encode calldata for the Universal Router contract
`viem@2.37.13`	Ethereum client (reads, writes, signing) — pin to this version for PancakeSwap compatibility

Step 1: Set Up Viem Clients

import { createPublicClient, createWalletClient, http } from 'viem'
import { bsc } from 'viem/chains'
import { privateKeyToAccount } from 'viem/accounts'

const publicClient = createPublicClient({
  chain: bsc,
  transport: http('https://bsc-dataseed1.binance.org'),
})

const account = privateKeyToAccount(process.env.PRIVATE_KEY as `0x${string}`)
const walletClient = createWalletClient({
  account,
  chain: bsc,
  transport: http('https://bsc-dataseed1.binance.org'),
})

Step 2: Define Tokens

import { ChainId, Token } from '@pancakeswap/sdk'
import { Native } from '@pancakeswap/swap-sdk-evm'

const chainId = ChainId.BSC // 56

// Native BNB (no address)
const BNB = Native.onChain(chainId)

// ERC-20 tokens
const CAKE = new Token(
  chainId,
  '0x0E09FaBB73Bd3Ade0a17ECC321fD13a19e81cE82',
  18,
  'CAKE',
  'PancakeSwap Token',
)

const USDT = new Token(
  chainId,
  '0x55d398326f99059fF775485246999027B3197955',
  18,
  'USDT',
  'Tether USD',
)

Step 3: Fetch Candidate Pools

import { SmartRouter, PoolType } from '@pancakeswap/smart-router'
import { TradeType } from '@pancakeswap/sdk'
import { CurrencyAmount } from '@pancakeswap/swap-sdk-core'

const amountIn = CurrencyAmount.fromRawAmount(
  BNB,
  BigInt('1000000000000000000'), // 1 BNB
)

// Fetch all relevant pool types in parallel
const [v2Pools, v3Pools, stablePools] = await Promise.all([
  SmartRouter.getV2CandidatePools({
    onChainProvider: () => publicClient,
    currencyA: BNB,
    currencyB: CAKE,
  }),
  SmartRouter.getV3CandidatePools({
    onChainProvider: () => publicClient,
    subgraphProvider: undefined, // optional — speeds up pool discovery
    currencyA: BNB,
    currencyB: CAKE,
  }),
  SmartRouter.getStableCandidatePools({
    onChainProvider: () => publicClient,
    currencyA: BNB,
    currencyB: CAKE,
  }),
])

const pools = [...v2Pools, ...v3Pools, ...stablePools]

Performance tip: If you're building a UI, consider caching pools for 30–60 seconds and only re-fetching when the user changes tokens or chain.

Infinity (v4) pool access: The Smart Router SDK's Infinity pool integration is still evolving. For reliable Infinity CL and Infinity Bin pool access today, use Method 1 (Routing API) — it automatically considers all pool types including Infinity on BSC and Base with no extra setup required.

Step 4: Find Best Trade

const trade = await SmartRouter.getBestTrade(amountIn, CAKE, TradeType.EXACT_INPUT, {
  gasPriceWei: () => publicClient.getGasPrice(),
  maxHops: 3,
  maxSplits: 4,
  poolProvider: SmartRouter.createStaticPoolProvider(pools),
  quoteProvider: SmartRouter.createQuoteProvider({
    onChainProvider: () => publicClient,
  }),
  allowedPoolTypes: [PoolType.V2, PoolType.V3, PoolType.STABLE],
})

// Always check price impact before proceeding
if (parseFloat(trade.priceImpact.toSignificant(4)) > 2) {
  console.warn(`⚠️  High price impact: ${trade.priceImpact.toSignificant(4)}%`)
}

console.log('Output:', trade.outputAmount.toSignificant(6), CAKE.symbol)
console.log('Route:', trade.routes.map((r) => r.type).join(' + '))

Step 5: Approve Tokens

Skip this step if the input currency is native BNB/ETH — native currency does not need approval.

import { erc20Abi } from 'viem'
import {
  PancakeSwapUniversalRouter,
  getUniversalRouterAddress,
} from '@pancakeswap/universal-router-sdk'

const PERMIT2_ADDRESS = '0x000000000022D473030F116dDEE9F6B43aC78BA3' as const

async function ensureTokenApproved(
  tokenAddress: `0x${string}`,
  owner: `0x${string}`,
  chainId: number,
) {
  // Step 1: Approve Permit2 contract (one-time per token, per wallet)
  const permit2Allowance = await publicClient.readContract({
    address: tokenAddress,
    abi: erc20Abi,
    functionName: 'allowance',
    args: [owner, PERMIT2_ADDRESS],
  })

  const MAX_UINT256 = BigInt('0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff')
  if (permit2Allowance < MAX_UINT256 / 2n) {
    const hash = await walletClient.writeContract({
      address: tokenAddress,
      abi: erc20Abi,
      functionName: 'approve',
      args: [PERMIT2_ADDRESS, MAX_UINT256],
    })
    await publicClient.waitForTransactionReceipt({ hash })
    console.log('✅ Permit2 approved')
  }

  // Step 2: Approve the Universal Router via Permit2 (per-swap, via signature OR transaction)
  // The Universal Router SDK handles this via inputTokenPermit in options.
  // For simplicity, approve the Universal Router directly instead:
  const routerAddress = getUniversalRouterAddress(chainId) as `0x${string}`
  const routerAllowance = await publicClient.readContract({
    address: tokenAddress,
    abi: erc20Abi,
    functionName: 'allowance',
    args: [owner, routerAddress],
  })

  if (routerAllowance < MAX_UINT256 / 2n) {
    const hash = await walletClient.writeContract({
      address: tokenAddress,
      abi: erc20Abi,
      functionName: 'approve',
      args: [routerAddress, MAX_UINT256],
    })
    await publicClient.waitForTransactionReceipt({ hash })
    console.log('✅ Universal Router approved')
  }
}

Step 6: Encode and Send the Transaction

import {
  PancakeSwapUniversalRouter,
  getUniversalRouterAddress,
} from '@pancakeswap/universal-router-sdk'
import { Percent } from '@pancakeswap/sdk'

const slippage = new Percent(50, 10000) // 0.5%
const deadline = BigInt(Math.floor(Date.now() / 1000) + 60 * 20) // 20 min

// Encode the swap calldata
const { calldata, value } = PancakeSwapUniversalRouter.swapERC20CallParameters(trade, {
  slippageTolerance: slippage,
  recipient: account.address,
  deadlineOrPreviousBlockhash: deadline,
})

// Send the transaction
const hash = await walletClient.sendTransaction({
  to: getUniversalRouterAddress(chainId) as `0x${string}`,
  data: calldata as `0x${string}`,
  value: BigInt(value), // Non-zero only when input is native BNB/ETH
  gas: 400000n, // Overestimate — unspent gas is refunded
})

const receipt = await publicClient.waitForTransactionReceipt({ hash })
if (receipt.status === 'reverted') {
  throw new Error(`Swap reverted: ${receipt.transactionHash}`)
}
console.log('✅ Swap confirmed:', receipt.transactionHash)

Exact Output Swaps

To swap for a precise output amount (e.g., "I want exactly 100 USDT"):

const amountOut = CurrencyAmount.fromRawAmount(
  USDT,
  BigInt('100000000000000000000'), // 100 USDT (18 decimals)
)

const trade = await SmartRouter.getBestTrade(
  amountOut,
  BNB, // currencyIn — note: swapped argument order for EXACT_OUTPUT
  TradeType.EXACT_OUTPUT,
  {
    gasPriceWei: () => publicClient.getGasPrice(),
    maxHops: 3,
    maxSplits: 4,
    poolProvider: SmartRouter.createStaticPoolProvider(pools),
    quoteProvider: SmartRouter.createQuoteProvider({ onChainProvider: () => publicClient }),
  },
)

console.log('Max BNB to spend:', trade.inputAmount.toSignificant(6))

// Encode with maximumAmountIn applied automatically via slippageTolerance
const { calldata, value } = PancakeSwapUniversalRouter.swapERC20CallParameters(trade, {
  slippageTolerance: new Percent(50, 10000),
  recipient: account.address,
  deadlineOrPreviousBlockhash: deadline,
})

Method 3: Direct V2 Router Contract

Best for: Simple BSC swaps, Solidity integrations, or when you want zero SDK dependencies. Only supports V2 pools — no V3 or StableSwap.

V2 Router Address (BSC Mainnet)

0x10ED43C718714eb63d5aA57B78B54704E256024E

V2 Router ABI (subset)

const PANCAKE_V2_ROUTER_ABI = [
  {
    name: 'swapExactETHForTokens',
    type: 'function',
    stateMutability: 'payable',
    inputs: [
      { name: 'amountOutMin', type: 'uint256' },
      { name: 'path', type: 'address[]' },
      { name: 'to', type: 'address' },
      { name: 'deadline', type: 'uint256' },
    ],
    outputs: [{ name: 'amounts', type: 'uint256[]' }],
  },
  {
    name: 'swapExactTokensForETH',
    type: 'function',
    stateMutability: 'nonpayable',
    inputs: [
      { name: 'amountIn', type: 'uint256' },
      { name: 'amountOutMin', type: 'uint256' },
      { name: 'path', type: 'address[]' },
      { name: 'to', type: 'address' },
      { name: 'deadline', type: 'uint256' },
    ],
    outputs: [{ name: 'amounts', type: 'uint256[]' }],
  },
  {
    name: 'swapExactTokensForTokens',
    type: 'function',
    stateMutability: 'nonpayable',
    inputs: [
      { name: 'amountIn', type: 'uint256' },
      { name: 'amountOutMin', type: 'uint256' },
      { name: 'path', type: 'address[]' },
      { name: 'to', type: 'address' },
      { name: 'deadline', type: 'uint256' },
    ],
    outputs: [{ name: 'amounts', type: 'uint256[]' }],
  },
  // Fee-on-transfer variant (SafeMoon-style tokens)
  {
    name: 'swapExactTokensForTokensSupportingFeeOnTransferTokens',
    type: 'function',
    stateMutability: 'nonpayable',
    inputs: [
      { name: 'amountIn', type: 'uint256' },
      { name: 'amountOutMin', type: 'uint256' },
      { name: 'path', type: 'address[]' },
      { name: 'to', type: 'address' },
      { name: 'deadline', type: 'uint256' },
    ],
    outputs: [],
  },
  {
    name: 'getAmountsOut',
    type: 'function',
    stateMutability: 'view',
    inputs: [
      { name: 'amountIn', type: 'uint256' },
      { name: 'path', type: 'address[]' },
    ],
    outputs: [{ name: 'amounts', type: 'uint256[]' }],
  },
] as const

const V2_ROUTER = '0x10ED43C718714eb63d5aA57B78B54704E256024E' as const
const WBNB = '0xbb4CdB9CBd36B01bD1cBaEBF2De08d9173bc095c' as const
const CAKE = '0x0E09FaBB73Bd3Ade0a17ECC321fD13a19e81cE82' as const

V2 Swap Example (BNB → CAKE)

import { parseEther } from 'viem'

const slippageBps = 50n // 0.5%
const deadline = BigInt(Math.floor(Date.now() / 1000) + 60 * 20)

// 1. Get quote
const amounts = await publicClient.readContract({
  address: V2_ROUTER,
  abi: PANCAKE_V2_ROUTER_ABI,
  functionName: 'getAmountsOut',
  args: [parseEther('0.1'), [WBNB, CAKE]],
})
const expectedOut = amounts[1]
const minOut = (expectedOut * (10000n - slippageBps)) / 10000n

// 2. Approve router for the input token (skip for BNB input)

// 3. Execute
const hash = await walletClient.writeContract({
  address: V2_ROUTER,
  abi: PANCAKE_V2_ROUTER_ABI,
  functionName: 'swapExactETHForTokens',
  args: [minOut, [WBNB, CAKE], account.address, deadline],
  value: parseEther('0.1'),
})

Multi-hop V2 (BNB → USDT → CAKE)

// Simply extend the path array
const amounts = await publicClient.readContract({
  address: V2_ROUTER,
  abi: PANCAKE_V2_ROUTER_ABI,
  functionName: 'getAmountsOut',
  args: [parseEther('0.1'), [WBNB, USDT_BSC, CAKE]],
})

Token Approval Reference

Scenario	What to Approve	Where
Smart Router / Universal Router	Token → Permit2	One-time per token
Smart Router / Universal Router	Permit2 → Universal Router	Per session (or use sig)
Direct V2 Router	Token → V2 Router	One-time per token
Native BNB/ETH input	No approval needed	—

V3 Fee Tiers

import { FeeAmount } from '@pancakeswap/v3-sdk'

FeeAmount.LOWEST // 100   bps = 0.01%  — stablecoin pairs (USDT/USDC)
FeeAmount.LOW // 500   bps = 0.05%  — stable-ish pairs
FeeAmount.MEDIUM // 2500  bps = 0.25%  — most standard pairs (default)
FeeAmount.HIGH // 10000 bps = 1%     — exotic or highly volatile pairs

Critical Implementation Notes

TypeScript Import Conventions

Use import type (or inline type modifier) for any import that is only used as a TypeScript type — never at runtime. This keeps bundles clean and avoids circular-dependency issues.

// ✅ Correct — Currency is only used in a type annotation
import { type Currency, TradeType, Percent } from '@pancakeswap/sdk'
import type { SmartRouterTrade } from '@pancakeswap/smart-router'

// ❌ Wrong — Currency is only a type, don't import it as a value
import { Currency, TradeType, Percent } from '@pancakeswap/sdk'

Slippage Guidelines

Token Type	Recommended Slippage
Stablecoins (USDT/USDC/BUSD pairs)	0.01–0.1%
Large caps (CAKE, BNB, ETH)	0.3–0.5%
Mid/small caps	0.5–2%
Fee-on-transfer / reflection tokens	5–12%
New meme tokens	5–15%

Never set 0% slippage in production. Every block's price movement will cause the transaction to revert.

Native BNB/ETH Handling

Pass Native.onChain(chainId) as the currency — the Smart Router and Universal Router handle WRAP_ETH / UNWRAP_WETH commands automatically.
For direct V2 calls: use swapExactETHForTokens with value: amountIn.
value in the encoded calldata will be non-zero only when the input is native. Always pass it when sending the transaction.

Fee-on-Transfer Tokens (Reflection Tokens)

These tokens deduct a fee on every transfer, so the router receives less than amountIn.
On V2: use swapExactTokensForTokensSupportingFeeOnTransferTokens or swapExactETHForTokensSupportingFeeOnTransferTokens.
The Smart Router detects these automatically and routes accordingly.
Always set slippage ≥ the token's transfer fee (e.g., 5% token fee → use ≥5% slippage).

Quote Staleness

Re-fetch the trade quote if it is more than 15–30 seconds old before sending.
Stale quotes frequently revert with INSUFFICIENT_OUTPUT_AMOUNT.

Gas Estimates

Swap Type	Approx. Gas
V2 single-hop	~150,000
V3 single-hop	~180,000
V2+V3 two-hop	~300,000
Mixed 3-hop	~400,000–600,000
With Permit2 signature	+~40,000

Always use publicClient.estimateGas() in production; hard-coded values can under-estimate on complex routes.

Error Handling

Common Revert Reasons

Error String	Cause	Fix
`INSUFFICIENT_OUTPUT_AMOUNT`	Slippage exceeded (price moved)	Increase `slippageTolerance` or re-quote
`EXCESSIVE_INPUT_AMOUNT`	Slippage exceeded for exact-output swap	Increase `slippageTolerance` or re-quote
`EXPIRED`	`deadline` timestamp is in the past	Re-fetch quote with a fresh deadline
`TRANSFER_FAILED`	Fee-on-transfer token, incorrect method	Use `SupportingFeeOnTransferTokens` variant
`STF` (SafeTransferFrom failed)	Token not approved to router or Permit2	Run `ensureTokenApproved()` first
`TransactionExecutionError`	General on-chain failure	Decode with `publicClient.call()` below

Debugging a Revert

// Simulate the transaction to get the revert reason
try {
  await publicClient.call({
    to: getUniversalRouterAddress(chainId) as `0x${string}`,
    data: calldata as `0x${string}`,
    value: BigInt(value),
    account: account.address,
  })
} catch (err: unknown) {
  // viem throws with the decoded revert reason
  console.error('Revert reason:', (err as Error).message)
}

Frontend Integration (React + wagmi)

For React frontends, use wagmi hooks alongside the Smart Router SDK:

npm install wagmi@2.17.5 viem@2.37.13 @tanstack/react-query

import { useWalletClient, usePublicClient, useChainId } from 'wagmi'
import { useMutation } from '@tanstack/react-query'
import { type Currency, TradeType, Percent } from '@pancakeswap/sdk'
import { CurrencyAmount } from '@pancakeswap/swap-sdk-core'
import { SmartRouter } from '@pancakeswap/smart-router'
import {
  PancakeSwapUniversalRouter,
  getUniversalRouterAddress,
} from '@pancakeswap/universal-router-sdk'

type SwapVariables = { amountIn: bigint; tokenIn: Currency; tokenOut: Currency }

function useSwap() {
  const chainId = useChainId()
  const { data: walletClient } = useWalletClient()
  const publicClient = usePublicClient()

  return useMutation<`0x${string}`, Error, SwapVariables>({
    mutationFn: async ({ amountIn, tokenIn, tokenOut }) => {
      if (!walletClient || !publicClient) throw new Error('Wallet not connected')

      // 1. Fetch pools
      const pools = await fetchPancakePools(publicClient, tokenIn, tokenOut, chainId)

      // 2. Get best trade
      const trade = await SmartRouter.getBestTrade(
        CurrencyAmount.fromRawAmount(tokenIn, amountIn),
        tokenOut,
        TradeType.EXACT_INPUT,
        {
          gasPriceWei: () => publicClient.getGasPrice(),
          maxHops: 3,
          maxSplits: 4,
          poolProvider: SmartRouter.createStaticPoolProvider(pools),
          quoteProvider: SmartRouter.createQuoteProvider({ onChainProvider: () => publicClient }),
        },
      )
      if (!trade) throw new Error('No route found for this token pair')

      // 3. Encode
      const { calldata, value } = PancakeSwapUniversalRouter.swapERC20CallParameters(trade, {
        slippageTolerance: new Percent(50, 10000),
        recipient: walletClient.account.address,
        deadlineOrPreviousBlockhash: BigInt(Math.floor(Date.now() / 1000) + 1200),
      })

      // 4. Send
      return walletClient.sendTransaction({
        to: getUniversalRouterAddress(chainId) as `0x${string}`,
        data: calldata as `0x${string}`,
        value: BigInt(value),
      })
    },
  })
}

Complete Working Example: BNB → CAKE

import { createPublicClient, createWalletClient, http } from 'viem'
import { bsc } from 'viem/chains'
import { privateKeyToAccount } from 'viem/accounts'
import { ChainId, Token, TradeType, Percent } from '@pancakeswap/sdk'
import { Native } from '@pancakeswap/swap-sdk-evm'
import { CurrencyAmount } from '@pancakeswap/swap-sdk-core'
import { SmartRouter, PoolType } from '@pancakeswap/smart-router'
import {
  PancakeSwapUniversalRouter,
  getUniversalRouterAddress,
} from '@pancakeswap/universal-router-sdk'

const chainId = ChainId.BSC
const account = privateKeyToAccount(process.env.PRIVATE_KEY as `0x${string}`)

const publicClient = createPublicClient({
  chain: bsc,
  transport: http('https://bsc-dataseed1.binance.org'),
})
const walletClient = createWalletClient({
  account,
  chain: bsc,
  transport: http('https://bsc-dataseed1.binance.org'),
})

const BNB = Native.onChain(chainId)
const CAKE = new Token(chainId, '0x0E09FaBB73Bd3Ade0a17ECC321fD13a19e81cE82', 18, 'CAKE')

async function swapBNBforCAKE(bnbAmountWei: bigint) {
  const amountIn = CurrencyAmount.fromRawAmount(BNB, bnbAmountWei)

  // 1. Fetch candidate pools (V2 + V3; stable not relevant for BNB/CAKE)
  const [v2Pools, v3Pools] = await Promise.all([
    SmartRouter.getV2CandidatePools({
      onChainProvider: () => publicClient,
      currencyA: BNB,
      currencyB: CAKE,
    }),
    SmartRouter.getV3CandidatePools({
      onChainProvider: () => publicClient,
      subgraphProvider: undefined,
      currencyA: BNB,
      currencyB: CAKE,
    }),
  ])

  // 2. Find best route
  const trade = await SmartRouter.getBestTrade(amountIn, CAKE, TradeType.EXACT_INPUT, {
    gasPriceWei: () => publicClient.getGasPrice(),
    maxHops: 3,
    maxSplits: 4,
    poolProvider: SmartRouter.createStaticPoolProvider([...v2Pools, ...v3Pools]),
    quoteProvider: SmartRouter.createQuoteProvider({ onChainProvider: () => publicClient }),
    allowedPoolTypes: [PoolType.V2, PoolType.V3],
  })

  const impact = parseFloat(trade.priceImpact.toSignificant(4))
  if (impact > 2) console.warn(`⚠️  High price impact: ${impact}%`)

  console.log(
    `Swapping ${amountIn.toSignificant(4)} BNB → ~${trade.outputAmount.toSignificant(4)} CAKE`,
  )

  // 3. Encode calldata
  const { calldata, value } = PancakeSwapUniversalRouter.swapERC20CallParameters(trade, {
    slippageTolerance: new Percent(50, 10000), // 0.5%
    recipient: account.address,
    deadlineOrPreviousBlockhash: BigInt(Math.floor(Date.now() / 1000) + 1200),
  })

  // 4. Send (no token approval needed — input is native BNB)
  const hash = await walletClient.sendTransaction({
    to: getUniversalRouterAddress(chainId) as `0x${string}`,
    data: calldata as `0x${string}`,
    value: BigInt(value),
    gas: 400000n,
  })

  const receipt = await publicClient.waitForTransactionReceipt({ hash })
  if (receipt.status === 'reverted') throw new Error(`Swap reverted: ${hash}`)

  console.log('✅ Confirmed:', receipt.transactionHash)
  return receipt
}

await swapBNBforCAKE(BigInt('100000000000000000')) // 0.1 BNB

name	swap-integration
slug	pcs-swap-integration
description	Integrate PancakeSwap swaps into applications. Use when user says "integrate swaps", "pancakeswap", "smart router", "add swap functionality", "build a swap frontend", "create a swap script", "smart contract swap integration", "use Universal Router", or mentions swapping tokens via PancakeSwap.
homepage	https://github.com/pancakeswap/pancakeswap-ai
allowed-tools	Read, Write, Edit, Glob, Grep, Bash(npm:), Bash(npx:), Bash(yarn:), Bash(curl:), WebFetch, Task(subagent_type:swap-integration-expert)
model	opus
license	MIT
metadata	{"author":"pancakeswap","version":"1.0.0","openclaw":{"homepage":"https://github.com/pancakeswap/pancakeswap-ai","os":["macos","linux"],"requires":{"bins":["curl","jq"],"anyBins":["cast","python3","node","open","xdg-open"]},"install":[{"kind":"brew","formula":"curl","bins":["curl"]},{"kind":"brew","formula":"jq","bins":["jq"]},{"kind":"brew","formula":"foundry","bins":["cast"]}]}}

name	swap-integration
slug	pcs-swap-integration
description	Integrate PancakeSwap swaps into applications. Use when user says "integrate swaps", "pancakeswap", "smart router", "add swap functionality", "build a swap frontend", "create a swap script", "smart contract swap integration", "use Universal Router", or mentions swapping tokens via PancakeSwap.
homepage	https://github.com/pancakeswap/pancakeswap-ai
allowed-tools	Read, Write, Edit, Glob, Grep, Bash(npm:), Bash(npx:), Bash(yarn:), Bash(curl:), WebFetch, Task(subagent_type:swap-integration-expert)
model	opus
license	MIT
metadata	{"author":"pancakeswap","version":"1.0.0","openclaw":{"homepage":"https://github.com/pancakeswap/pancakeswap-ai","os":["macos","linux"],"requires":{"bins":["curl","jq"],"anyBins":["cast","python3","node","open","xdg-open"]},"install":[{"kind":"brew","formula":"curl","bins":["curl"]},{"kind":"brew","formula":"jq","bins":["jq"]},{"kind":"brew","formula":"foundry","bins":["cast"]}]}}

swap-integration

More from this repository

More from this repository

Swap Integration

Quick Decision Guide

Protocol Types

Supported Chains

Key Token Addresses

BSC Mainnet (Chain ID: 56)

BSC Testnet (Chain ID: 97)

Universal Router Addresses

Method 1: PancakeSwap Routing API (Simplest)

Get a Quote

API Parameters

TypeScript Fetch Example

Method 2: Smart Router SDK + Universal Router SDK

Installation

Package Roles

Step 1: Set Up Viem Clients

Step 2: Define Tokens

Step 3: Fetch Candidate Pools

Step 4: Find Best Trade

Step 5: Approve Tokens

Step 6: Encode and Send the Transaction

Exact Output Swaps

Method 3: Direct V2 Router Contract

V2 Router Address (BSC Mainnet)

V2 Router ABI (subset)

V2 Swap Example (BNB → CAKE)

Multi-hop V2 (BNB → USDT → CAKE)

Token Approval Reference

V3 Fee Tiers

Critical Implementation Notes

TypeScript Import Conventions

Slippage Guidelines

Native BNB/ETH Handling

Fee-on-Transfer Tokens (Reflection Tokens)

Quote Staleness

Gas Estimates

Error Handling

Common Revert Reasons

Debugging a Revert

Frontend Integration (React + wagmi)

Complete Working Example: BNB → CAKE

Swap Integration

Quick Decision Guide

Protocol Types

Supported Chains

Key Token Addresses

BSC Mainnet (Chain ID: 56)

BSC Testnet (Chain ID: 97)

Universal Router Addresses

Method 1: PancakeSwap Routing API (Simplest)

Get a Quote

API Parameters

TypeScript Fetch Example

Method 2: Smart Router SDK + Universal Router SDK

Installation

Package Roles

Step 1: Set Up Viem Clients

Step 2: Define Tokens

Step 3: Fetch Candidate Pools

Step 4: Find Best Trade

Step 5: Approve Tokens

Step 6: Encode and Send the Transaction

Exact Output Swaps

Method 3: Direct V2 Router Contract

V2 Router Address (BSC Mainnet)

V2 Router ABI (subset)

V2 Swap Example (BNB → CAKE)

Multi-hop V2 (BNB → USDT → CAKE)

Token Approval Reference

V3 Fee Tiers

Critical Implementation Notes

TypeScript Import Conventions

Slippage Guidelines

Native BNB/ETH Handling

Fee-on-Transfer Tokens (Reflection Tokens)

Quote Staleness

Gas Estimates