Swapper Integration

Your Role: Research → Implement → Test → Document, following battle-tested patterns from 13+ existing swapper integrations.

Workflow

Phase 0: Pre-Research (Use WebFetch / WebSearch)

BEFORE asking the user for anything, proactively research the swapper online:

1. Search for official documentation:

   Search: "[SwapperName] API documentation"
   Search: "[SwapperName] developer docs"
   Search: "[SwapperName] swagger api"
   

2. Find their website and look for:

   • API docs link
   • Developer portal
   • GitHub repos with examples
   • Public API endpoints
   • Known integrations

3. Fetch their API docs using WebFetch:

   • Main documentation page
   • Swagger/OpenAPI spec (if available)
   • Example requests/responses

4. Research chain support:

   Search: "[SwapperName] supported chains"
   Search: "[SwapperName] which blockchains"
   

5. Find existing integrations:

   Search: "github [SwapperName] integration example"
   Search: "[SwapperName] typescript sdk"
   

Then, compile what you found and ask the user ONLY for what you couldn't find or need confirmation on.

Phase 1: Information Gathering

Use the AskUserQuestion tool to gather missing information with structured prompts.

Based on your Phase 0 research, ask the user for:

1. API Access (if needed):

   • API key for production (or staging)
   • Any authentication requirements you found
   • Confirmation of API endpoints you discovered

2. Chain Support Confirmation:

   • Verify the chains you found are correct
   • Ask about any limitations or special requirements per chain
   • Confirm chain naming convention (ethereum vs 1 vs mainnet)

3. Critical API Behaviors (if not clear from docs):

   • Slippage format: percentage (1=1%), decimal (0.01=1%), or basis points (100=1%)?
   • Address format: checksummed required?
   • Native token handling: marker address? which one?
   • Min/max trade amounts?
   • Quote expiration time?

4. Brand Assets:

   • Confirm official name and capitalization
   • Request logo/icon (128x128+ PNG preferred)

5. Known Issues:

   • Any quirks they're aware of?
   • Previous integration attempts or examples?

Example Multi-Question Prompt:

AskUserQuestion({
  questions: [
    {
      question: "Do we have an API key for [Swapper]?",
      header: "API Key",
      multiSelect: false,
      options: [
        { label: "Yes, I have it", description: "I'll provide the API key" },
        { label: "No, but we can get one", description: "I'll obtain an API key" },
        { label: "No API key needed", description: "API is public/unauthenticated" }
      ]
    },
    {
      question: "Which chains should we support initially?",
      header: "Chain Support",
      multiSelect: true,
      options: [
        { label: "Ethereum", description: "Ethereum mainnet" },
        { label: "Polygon", description: "Polygon PoS" },
        { label: "Arbitrum", description: "Arbitrum One" },
        { label: "All supported chains", description: "Enable all chains the API supports" }
      ]
    }
  ]
})

Phase 2: Deep Research & Pattern Analysis

IMPORTANT: Study existing swappers BEFORE writing any code. This prevents reimplementing solved problems.

Step 1: Identify Swapper Category

Based on API research, determine the swapper type:

EVM Direct Transaction (Most Common):

• Characteristics: Single EVM chain, returns transaction data, user signs & broadcasts
• Examples: Bebop, 0x, Portals
• Key Files: bebopTransactionMetadata, zrxTransactionMetadata, portalsTransactionMetadata
• Choose this if: API returns {to, data, value, gas} transaction object

Deposit-to-Address (Cross-Chain/Async):

• Characteristics: User sends to deposit address, swapper handles execution asynchronously
• Examples: Chainflip, NEAR Intents, THORChain
• Key Files: Uses [swapper]Specific metadata with depositAddress
• Choose this if: API returns deposit address and swap ID for tracking

Gasless Order-Based:

• Characteristics: Sign message not transaction, relayer executes, no gas
• Examples: CowSwap
• Key Files: Uses cowswapQuoteResponse, custom executeEvmMessage
• Choose this if: Uses EIP-712 message signing + order submission

Solana-Only:

• Characteristics: Solana transaction with instructions and ALTs
• Examples: Jupiter
• Key Files: jupiterQuoteResponse, solanaTransactionMetadata
• Choose this if: Solana ecosystem only

Chain-Specific (Sui/Tron/etc.):

• Characteristics: Custom transaction format for specific blockchain
• Examples: Cetus (Sui)
• Key Files: Chain-specific adapters and transaction metadata
• Choose this if: Non-EVM, non-Solana blockchain with custom SDK

Step 2: Study 2-3 Similar Swappers IN DEPTH

Read these files for your chosen swapper type:

# For EVM Direct Transaction (e.g., Bebop):
packages/swapper/src/swappers/BebopSwapper/
├── BebopSwapper.ts                # Swapper interface (usually just executeEvmTransaction)
├── endpoints.ts                   # SwapperApi implementation
├── types.ts                       # API request/response types
├── getBebopTradeQuote/
│   └── getBebopTradeQuote.ts     # Quote logic (WITH fee estimation)
├── getBebopTradeRate/
│   └── getBebopTradeRate.ts      # Rate logic (withOUT wallet, may use dummy address)
└── utils/
    ├── constants.ts               # Supported chains, native marker, defaults
    ├── bebopService.ts            # HTTP client with cache + API key injection
    ├── fetchFromBebop.ts          # API wrappers (fetchQuote, fetchPrice)
    └── helpers/
        └── helpers.ts             # Validation, rate calc, address helpers

Read these files for deposit-to-address (e.g., NEAR Intents):

packages/swapper/src/swappers/NearIntentsSwapper/
├── endpoints.ts                   # checkTradeStatus uses depositAddress from metadata
├── swapperApi/
│   ├── getTradeQuote.ts          # Stores depositAddress in nearIntentsSpecific
│   └── getTradeRate.ts
└── utils/
    ├── oneClickService.ts         # OneClick SDK initialization
    └── helpers/
        └── helpers.ts             # Asset mapping, status translation

Critical things to note while reading:

1. How do they call the API? (HTTP service pattern? SDK? Direct axios?)
2. How do they handle errors? (Monadic Result<T, SwapErrorRight> pattern)
3. How do they calculate rates? (getInputOutputRate util vs custom)
4. What metadata do they store in TradeQuoteStep?
5. How do they validate inputs? (Supported chains? Asset compatibility?)
6. How do they handle native tokens? (Marker address vs special field)
7. How do they convert API responses to our types?

Step 3: Review Common Patterns

Key Pattern: Monadic Error Handling

import { Err, Ok } from '@sniptt/monads'
import { makeSwapErrorRight } from '../../../utils'

// ALWAYS return Result<T, SwapErrorRight>, NEVER throw
const result = await someOperation()
if (result.isErr()) {
  return Err(makeSwapErrorRight({
    message: 'What went wrong',
    code: TradeQuoteError.QueryFailed,
    details: { context: 'here' }
  }))
}
return Ok(result.unwrap())

Key Pattern: HTTP Service with Caching

import { createCache, makeSwapperAxiosServiceMonadic } from '../../../utils'

const maxAge = 5 * 1000 // 5 seconds
const cachedUrls = ['/quote', '/price'] // which endpoints to cache

const serviceBase = createCache(maxAge, cachedUrls, {
  timeout: 10000,
  headers: {
    'Accept': 'application/json',
    'x-api-key': config.VITE_XYZ_API_KEY
  }
})

export const xyzService = makeSwapperAxiosServiceMonadic(serviceBase)

Key Pattern: Rate Limiting and Throttling

For chain adapters and swappers that directly interact with RPC endpoints or APIs:

import PQueue from 'p-queue'

// In constructor or module scope:
private requestQueue: PQueue = new PQueue({
  intervalCap: 1,    // 1 request per interval
  interval: 50,      // 50ms between requests
  concurrency: 1,    // 1 concurrent request at a time
})

// Wrap all external API/RPC calls:
const quote = await this.requestQueue.add(() =>
  swapperService.get('/quote', { params })
)

// For provider calls in chain adapters:
const balance = await this.requestQueue.add(() =>
  this.provider.getBalance(address)
)

When to use: Any swapper or chain adapter making direct RPC/API calls (especially public endpoints) Example implementations: MonadChainAdapter, PlasmaChainAdapter

Key Pattern: Rate Calculation

import { getInputOutputRate } from '../../../utils'

const rate = getInputOutputRate({
  sellAmountCryptoBaseUnit,
  buyAmountCryptoBaseUnit,
  sellAsset,
  buyAsset
})

Phase 3: Implementation (Step by Step)

Follow this EXACT order to avoid rework:

Step 1: Create Directory Structure

mkdir -p packages/swapper/src/swappers/[SwapperName]Swapper/{get[SwapperName]TradeQuote,get[SwapperName]TradeRate,utils/helpers}

Standard structure (EVM swappers):

[SwapperName]Swapper/
├── index.ts
├── [SwapperName]Swapper.ts
├── endpoints.ts
├── types.ts
├── get[SwapperName]TradeQuote/
│   └── get[SwapperName]TradeQuote.ts
├── get[SwapperName]TradeRate/
│   └── get[SwapperName]TradeRate.ts
└── utils/
    ├── constants.ts
    ├── [swapperName]Service.ts
    ├── fetchFrom[SwapperName].ts
    └── helpers/
        └── helpers.ts

Step 2: Implement Files in Order

2a. types.ts - API TypeScript Types

Define types EXACTLY matching the API response (log actual API responses to verify!):

import type { Address, Hex } from 'viem'

// Request types
export type [Swapper]QuoteRequest = {
  sellToken: Address
  buyToken: Address
  sellAmount: string
  slippage: number  // NOTE: document what format! (percentage, decimal, basis points)
  takerAddress: Address
  receiverAddress?: Address
  chainId: number
}

// Response types (match API exactly!)
export type [Swapper]QuoteResponse = {
  // Copy structure from actual API response
  buyAmount: string
  sellAmount: string
  transaction: {
    to: Address
    data: Hex
    value: Hex
    gas?: Hex
  }
  // ... rest of response
}

// Constants
export const [SWAPPER]_SUPPORTED_CHAIN_IDS: Record<number, string> = {
  1: 'ethereum',
  137: 'polygon',
  42161: 'arbitrum',
  // ...
}

2b. utils/constants.ts - Configuration

import type { AssetId, ChainId } from '@shapeshiftoss/caip'
import { ethChainId, polygonChainId, arbitrumChainId } from '@shapeshiftoss/caip'
import type { Address } from 'viem'

export const SUPPORTED_CHAIN_IDS = [
  ethChainId,
  polygonChainId,
  arbitrumChainId,
] as const

export type [Swapper]SupportedChainId = (typeof SUPPORTED_CHAIN_IDS)[number]

// Native token marker (if API uses one)
export const NATIVE_TOKEN_MARKER = '0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE' as Address

// Dummy address for rates (when no wallet connected)
export const DUMMY_ADDRESS = '0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045' as Address

// Default slippage if none provided
export const DEFAULT_SLIPPAGE_PERCENTAGE = '0.5' // 0.5%

2c. utils/helpers/helpers.ts - Helper Functions

import { fromAssetId, type AssetId } from '@shapeshiftoss/caip'
import { isToken } from '@shapeshiftoss/utils'
import { getAddress, type Address } from 'viem'
import { NATIVE_TOKEN_MARKER, SUPPORTED_CHAIN_IDS } from '../constants'

// Check if chain is supported
export const isSupportedChainId = (chainId: string): boolean => {
  return SUPPORTED_CHAIN_IDS.includes(chainId as any)
}

// Convert assetId to token address (with native token handling)
export const assetIdToToken = (assetId: AssetId): Address => {
  if (!isToken(assetId)) {
    return NATIVE_TOKEN_MARKER // Native token (ETH, MATIC, etc.)
  }
  const { assetReference } = fromAssetId(assetId)
  return getAddress(assetReference) // Checksum ERC20 address
}

// Convert ShapeShift chainId to API chain identifier
export const chainIdToChainRef = (chainId: string): string => {
  switch (chainId) {
    case ethChainId:
      return 'ethereum' // or '1' or 'mainnet' depending on API
    case polygonChainId:
      return 'polygon'
    // ...
    default:
      throw new Error(`Unsupported chainId: ${chainId}`)
  }
}

// Calculate rate from amounts
import { getInputOutputRate } from '../../../../utils'
export { getInputOutputRate } // Re-export for use in quote/rate files

2d. utils/[swapperName]Service.ts - HTTP Service

import { createCache, makeSwapperAxiosServiceMonadic } from '../../../utils'
import type { SwapperConfig } from '../../../types'

// Cache for 5 seconds (adjust based on API)
const maxAge = 5 * 1000

// Which endpoints to cache (usually /quote and /price)
const cachedUrls = ['/quote', '/price']

export const [swapperName]ServiceFactory = (config: SwapperConfig) => {
  const axiosConfig = {
    timeout: 10000,
    headers: {
      'Accept': 'application/json',
      'Content-Type': 'application/json',
      ...(config.VITE_[SWAPPER]_API_KEY && {
        'x-api-key': config.VITE_[SWAPPER]_API_KEY
      })
    }
  }

  const serviceBase = createCache(maxAge, cachedUrls, axiosConfig)
  return makeSwapperAxiosServiceMonadic(serviceBase)
}

export type [Swapper]Service = ReturnType<typeof [swapperName]ServiceFactory>

2e. utils/fetchFrom[SwapperName].ts - API Wrappers

import { type AssetId } from '@shapeshiftoss/caip'
import { bn } from '@shapeshiftoss/utils'
import { Err, Ok, type Result } from '@sniptt/monads'
import { getAddress, type Address } from 'viem'
import { makeSwapErrorRight } from '../../../utils'
import { TradeQuoteError, type SwapErrorRight } from '../../../types'
import type { [Swapper]Service } from './[swapperName]Service'
import type { [Swapper]QuoteRequest, [Swapper]QuoteResponse } from '../types'
import { assetIdToToken, chainIdToChainRef } from './helpers/helpers'

// Base URL for API
const BASE_URL = 'https://api.[swapper].com'

export type FetchQuoteParams = {
  sellAssetId: AssetId
  buyAssetId: AssetId
  sellAmountCryptoBaseUnit: string
  chainId: string
  takerAddress: string
  receiverAddress: string
  slippageTolerancePercentageDecimal: string
  affiliateBps: string
}

export const fetchQuote = async (
  params: FetchQuoteParams,
  service: [Swapper]Service
): Promise<Result<[Swapper]QuoteResponse, SwapErrorRight>> => {
  try {
    const {
      sellAssetId,
      buyAssetId,
      sellAmountCryptoBaseUnit,
      chainId,
      takerAddress,
      receiverAddress,
      slippageTolerancePercentageDecimal,
      affiliateBps
    } = params

    // Convert to API format
    const sellToken = assetIdToToken(sellAssetId)
    const buyToken = assetIdToToken(buyAssetId)
    const chainRef = chainIdToChainRef(chainId)

    // CRITICAL: Convert slippage to API format
    // ShapeShift format: 0.005 = 0.5%
    // Check API docs for their format!
    const slippagePercentage = bn(slippageTolerancePercentageDecimal)
      .times(100) // If API expects 0.5 for 0.5%
      .toNumber()

    // Checksum addresses (CRITICAL for many APIs)
    const checksummedTakerAddress = getAddress(takerAddress)
    const checksummedReceiverAddress = getAddress(receiverAddress)

    const requestBody: [Swapper]QuoteRequest = {
      sellToken,
      buyToken,
      sellAmount: sellAmountCryptoBaseUnit,
      slippage: slippagePercentage,
      takerAddress: checksummedTakerAddress,
      receiverAddress: checksummedReceiverAddress,
      chainId: chainRef,
      // Add affiliate if supported
      ...(affiliateBps !== '0' && { affiliateBps })
    }

    const maybeResponse = await service.post<[Swapper]QuoteResponse>(
      `${BASE_URL}/quote`,
      requestBody
    )

    if (maybeResponse.isErr()) {
      return Err(maybeResponse.unwrapErr())
    }

    const { data: response } = maybeResponse.unwrap()

    // Validate response has required fields
    if (!response.buyAmount || !response.transaction) {
      return Err(
        makeSwapErrorRight({
          message: 'Invalid response from API',
          code: TradeQuoteError.InvalidResponse,
          details: { response }
        })
      )
    }

    return Ok(response)
  } catch (error) {
    return Err(
      makeSwapErrorRight({
        message: 'Failed to fetch quote',
        code: TradeQuoteError.QueryFailed,
        cause: error
      })
    )
  }
}

// For rates (no wallet needed)
export type FetchPriceParams = Omit<FetchQuoteParams, 'takerAddress' | 'receiverAddress'> & {
  receiveAddress: string | undefined
}

export const fetchPrice = async (
  params: FetchPriceParams,
  service: [Swapper]Service
): Promise<Result<[Swapper]QuoteResponse, SwapErrorRight>> => {
  // Use dummy address if no wallet connected
  const address = params.receiveAddress
    ? getAddress(params.receiveAddress)
    : DUMMY_ADDRESS

  // IMPORTANT: Use same affiliate for both quote and rate to avoid delta!
  return fetchQuote(
    {
      ...params,
      takerAddress: address,
      receiverAddress: address
    },
    service
  )
}

2f. get[SwapperName]TradeQuote/get[SwapperName]TradeQuote.ts - Quote Logic

This is the MEAT of the implementation. It must:

1. Validate inputs (chain support, asset compatibility)
2. Fetch quote from API
3. Estimate network fees using chain adapter
4. Build complete TradeQuote object with all required fields
5. Handle errors monadic-ally

import { type AssetId } from '@shapeshiftoss/caip'
import { bn } from '@shapeshiftoss/utils'
import { Err, Ok, type Result } from '@sniptt/monads'
import { makeSwapErrorRight } from '../../../utils'
import {
  type CommonTradeQuoteInput,
  type GetEvmTradeQuoteInput,
  type SwapErrorRight,
  type SwapperDeps,
  type TradeQuote,
  TradeQuoteError
} from '../../../types'
import { fetchQuote } from '../utils/fetchFromBebop'
import { [swapperName]ServiceFactory } from '../utils/[swapperName]Service'
import {
  getInputOutputRate,
  isSupportedChainId
} from '../utils/helpers/helpers'
import { DUMMY_ADDRESS } from '../utils/constants'

export const get[SwapperName]TradeQuote = async (
  input: GetEvmTradeQuoteInput | CommonTradeQuoteInput,
  deps: SwapperDeps
): Promise<Result<TradeQuote, SwapErrorRight>> => {
  try {
    const {
      sellAsset,
      buyAsset,
      sellAmountIncludingProtocolFeesCryptoBaseUnit,
      sendAddress,
      receiveAddress,
      accountNumber,
      affiliateBps,
      slippageTolerancePercentageDecimal
    } = input

    const { config, assertGetEvmChainAdapter } = deps

    // Validation: Check chain support
    if (!isSupportedChainId(sellAsset.chainId)) {
      return Err(
        makeSwapErrorRight({
          message: `[${SwapperName.[SwapperName]}] Unsupported chainId: ${sellAsset.chainId}`,
          code: TradeQuoteError.UnsupportedChain,
          details: { chainId: sellAsset.chainId }
        })
      )
    }

    // Validation: Must be same chain
    if (sellAsset.chainId !== buyAsset.chainId) {
      return Err(
        makeSwapErrorRight({
          message: `[${SwapperName.[SwapperName]}] Cross-chain not supported`,
          code: TradeQuoteError.CrossChainNotSupported
        })
      )
    }

    // Validation: Prevent executable quotes with dummy address
    const takerAddress = sendAddress ?? receiveAddress
    if (takerAddress === DUMMY_ADDRESS) {
      return Err(
        makeSwapErrorRight({
          message: 'Cannot execute trade with dummy address',
          code: TradeQuoteError.UnknownError
        })
      )
    }

    // Fetch quote from API
    const service = [swapperName]ServiceFactory(config)
    const maybeQuoteResponse = await fetchQuote(
      {
        sellAssetId: sellAsset.assetId,
        buyAssetId: buyAsset.assetId,
        sellAmountCryptoBaseUnit: sellAmountIncludingProtocolFeesCryptoBaseUnit,
        chainId: sellAsset.chainId,
        takerAddress,
        receiverAddress: receiveAddress,
        slippageTolerancePercentageDecimal:
          slippageTolerancePercentageDecimal ?? DEFAULT_SLIPPAGE_PERCENTAGE,
        affiliateBps
      },
      service
    )

    if (maybeQuoteResponse.isErr()) {
      return Err(maybeQuoteResponse.unwrapErr())
    }

    const quoteResponse = maybeQuoteResponse.unwrap()

    // Get chain adapter for fee estimation
    const adapter = assertGetEvmChainAdapter(sellAsset.chainId)

    // Estimate network fees
    const { average: { gasPrice } } = await adapter.getGasFeeData()

    const networkFeeCryptoBaseUnit = bn(quoteResponse.transaction.gas ?? '0')
      .times(gasPrice)
      .toFixed(0)

    // Calculate rate
    const rate = getInputOutputRate({
      sellAmountCryptoBaseUnit: sellAmountIncludingProtocolFeesCryptoBaseUnit,
      buyAmountCryptoBaseUnit: quoteResponse.buyAmount,
      sellAsset,
      buyAsset
    })

    // Build TradeQuote
    const tradeQuote: TradeQuote = {
      id: crypto.randomUUID(),
      quoteOrRate: 'quote',
      rate,
      slippageTolerancePercentageDecimal,
      receiveAddress,
      affiliateBps,
      steps: [
        {
          buyAmountBeforeFeesCryptoBaseUnit: quoteResponse.buyAmount,
          buyAmountAfterFeesCryptoBaseUnit: quoteResponse.buyAmount, // or minus protocol fees
          sellAmountIncludingProtocolFeesCryptoBaseUnit,
          feeData: {
            networkFeeCryptoBaseUnit,
            protocolFees: {}, // or add protocol fees if any
          },
          rate,
          source: SwapperName.[SwapperName],
          buyAsset,
          sellAsset,
          accountNumber,
          allowanceContract: isNativeEvmAsset(sellAsset.assetId)
            ? undefined
            : quoteResponse.approvalTarget, // or constant approval contract
          estimatedExecutionTimeMs: undefined, // or from API
          // Store transaction metadata
          [swapperName]TransactionMetadata: {
            to: quoteResponse.transaction.to,
            data: quoteResponse.transaction.data,
            value: quoteResponse.transaction.value,
            gas: quoteResponse.transaction.gas
          }
        }
      ],
      swapperName: SwapperName.[SwapperName]
    }

    return Ok(tradeQuote)
  } catch (error) {
    return Err(
      makeSwapErrorRight({
        message: 'Failed to get trade quote',
        code: TradeQuoteError.UnknownError,
        cause: error
      })
    )
  }
}

2g. get[SwapperName]TradeRate/get[SwapperName]TradeRate.ts - Rate Logic

Similar to quote but:

• No wallet address required (use dummy or undefined)
• accountNumber is undefined
• May skip network fee estimation (or use cached/estimated)

import { Err, Ok, type Result } from '@sniptt/monads'
import { makeSwapErrorRight } from '../../../utils'
import {
  type GetTradeRateInput,
  type SwapErrorRight,
  type SwapperDeps,
  type TradeRate,
  TradeQuoteError
} from '../../../types'
import { fetchPrice } from '../utils/fetchFromBebop'
import { [swapperName]ServiceFactory } from '../utils/[swapperName]Service'
import { getInputOutputRate, isSupportedChainId } from '../utils/helpers/helpers'
import { DEFAULT_SLIPPAGE_PERCENTAGE } from '../utils/constants'

export const get[SwapperName]TradeRate = async (
  input: GetTradeRateInput,
  deps: SwapperDeps
): Promise<Result<TradeRate, SwapErrorRight>> => {
  try {
    const {
      sellAsset,
      buyAsset,
      sellAmountIncludingProtocolFeesCryptoBaseUnit,
      receiveAddress,
      affiliateBps,
      slippageTolerancePercentageDecimal
    } = input

    const { config } = deps

    // Same validation as quote
    if (!isSupportedChainId(sellAsset.chainId)) {
      return Err(
        makeSwapErrorRight({
          message: `[${SwapperName.[SwapperName]}] Unsupported chainId: ${sellAsset.chainId}`,
          code: TradeQuoteError.UnsupportedChain
        })
      )
    }

    if (sellAsset.chainId !== buyAsset.chainId) {
      return Err(
        makeSwapErrorRight({
          message: `[${SwapperName.[SwapperName]}] Cross-chain not supported`,
          code: TradeQuoteError.CrossChainNotSupported
        })
      )
    }

    // Fetch rate (uses dummy address if no receiveAddress)
    const service = [swapperName]ServiceFactory(config)
    const maybeRateResponse = await fetchPrice(
      {
        sellAssetId: sellAsset.assetId,
        buyAssetId: buyAsset.assetId,
        sellAmountCryptoBaseUnit: sellAmountIncludingProtocolFeesCryptoBaseUnit,
        chainId: sellAsset.chainId,
        receiveAddress,
        slippageTolerancePercentageDecimal:
          slippageTolerancePercentageDecimal ?? DEFAULT_SLIPPAGE_PERCENTAGE,
        affiliateBps
      },
      service
    )

    if (maybeRateResponse.isErr()) {
      return Err(maybeRateResponse.unwrapErr())
    }

    const rateResponse = maybeRateResponse.unwrap()

    // Calculate rate
    const rate = getInputOutputRate({
      sellAmountCryptoBaseUnit: sellAmountIncludingProtocolFeesCryptoBaseUnit,
      buyAmountCryptoBaseUnit: rateResponse.buyAmount,
      sellAsset,
      buyAsset
    })

    // Build TradeRate (similar to quote but accountNumber = undefined)
    const tradeRate: TradeRate = {
      id: crypto.randomUUID(),
      quoteOrRate: 'rate',
      rate,
      slippageTolerancePercentageDecimal,
      receiveAddress,
      affiliateBps,
      steps: [
        {
          buyAmountBeforeFeesCryptoBaseUnit: rateResponse.buyAmount,
          buyAmountAfterFeesCryptoBaseUnit: rateResponse.buyAmount,
          sellAmountIncludingProtocolFeesCryptoBaseUnit,
          feeData: {
            networkFeeCryptoBaseUnit: undefined, // Unknown for rate
            protocolFees: {}
          },
          rate,
          source: SwapperName.[SwapperName],
          buyAsset,
          sellAsset,
          accountNumber: undefined, // CRITICAL: Must be undefined for rate
          allowanceContract: isNativeEvmAsset(sellAsset.assetId)
            ? undefined
            : rateResponse.approvalTarget,
          estimatedExecutionTimeMs: undefined
        }
      ],
      swapperName: SwapperName.[SwapperName]
    }

    return Ok(tradeRate)
  } catch (error) {
    return Err(
      makeSwapErrorRight({
        message: 'Failed to get trade rate',
        code: TradeQuoteError.UnknownError,
        cause: error
      })
    )
  }
}

2h. endpoints.ts - SwapperApi Implementation

import { isNativeEvmAsset } from '@shapeshiftoss/utils'
import { bn } from '@shapeshiftoss/utils'
import { fromHex, type Hex } from 'viem'
import { checkEvmSwapStatus } from '../../utils'
import type {
  CommonTradeQuoteInput,
  GetEvmTradeQuoteInput,
  GetTradeRateInput,
  GetUnsignedEvmTransactionArgs,
  SwapperApi,
  SwapperDeps,
  TradeQuote,
  TradeRate,
  TradeQuoteResult,
  TradeRateResult
} from '../../types'
import { get[SwapperName]TradeQuote } from './get[SwapperName]TradeQuote/get[SwapperName]TradeQuote'
import { get[SwapperName]TradeRate } from './get[SwapperName]TradeRate/get[SwapperName]TradeRate'

export const [swapperName]Api: SwapperApi = {
  getTradeQuote: async (
    input: GetEvmTradeQuoteInput | CommonTradeQuoteInput,
    deps: SwapperDeps
  ): Promise<TradeQuoteResult> => {
    const maybeTradeQuote = await get[SwapperName]TradeQuote(input, deps)
    return maybeTradeQuote.map(quote => [quote])
  },

  getTradeRate: async (
    input: GetTradeRateInput,
    deps: SwapperDeps
  ): Promise<TradeRateResult> => {
    const maybeTradeRate = await get[SwapperName]TradeRate(input, deps)
    return maybeTradeRate.map(rate => [rate])
  },

  getUnsignedEvmTransaction: async (
    args: GetUnsignedEvmTransactionArgs
  ) => {
    const {
      tradeQuote,
      chainId,
      from,
      stepIndex,
      assertGetEvmChainAdapter
    } = args

    const step = tradeQuote.steps[stepIndex]
    const metadata = step.[swapperName]TransactionMetadata

    if (!metadata) {
      throw new Error('Missing transaction metadata')
    }

    const adapter = assertGetEvmChainAdapter(chainId)

    // Convert hex values to decimal strings (CRITICAL!)
    const value = metadata.value
      ? fromHex(metadata.value as Hex, 'bigint').toString()
      : '0'

    const gasLimit = metadata.gas
      ? fromHex(metadata.gas as Hex, 'bigint').toString()
      : undefined

    // Build EVM transaction
    return {
      chainId: Number(fromChainId(chainId).chainReference),
      to: metadata.to,
      from,
      data: metadata.data,
      value,
      gasLimit, // or use adapter.getFeeData() if not provided
    }
  },

  getEvmTransactionFees: async (args: GetUnsignedEvmTransactionArgs) => {
    const { tradeQuote, chainId, assertGetEvmChainAdapter, stepIndex } = args

    const step = tradeQuote.steps[stepIndex]
    const adapter = assertGetEvmChainAdapter(chainId)

    // Get current gas price
    const { average: { gasPrice } } = await adapter.getGasFeeData()

    // Use API gas estimate or node estimate
    const metadata = step.[swapperName]TransactionMetadata
    const apiGasEstimate = metadata?.gas
      ? fromHex(metadata.gas as Hex, 'bigint').toString()
      : '0'

    // Take max of API and node estimates (with buffer)
    const networkFeeCryptoBaseUnit = bn
      .max(step.feeData.networkFeeCryptoBaseUnit ?? '0', apiGasEstimate)
      .times(1.15) // 15% buffer
      .toFixed(0)

    return networkFeeCryptoBaseUnit
  },

  checkTradeStatus: checkEvmSwapStatus // Standard EVM status check
}

2i. [SwapperName]Swapper.ts - Swapper Interface

For most EVM swappers, this is simple:

import { executeEvmTransaction } from '../utils'
import type { Swapper } from '../../types'

export const [swapperName]Swapper: Swapper = {
  executeEvmTransaction
}

For deposit-to-address or custom execution, implement custom logic here.

2j. index.ts - Exports

export { [swapperName]Api } from './endpoints'
export { [swapperName]Swapper } from './[SwapperName]Swapper'
export * from './types'
export * from './utils/constants'

Step 3: Add Swapper-Specific Metadata (ONLY if needed!)

Skip this step if your swapper is a direct transaction swapper (like Bebop, 0x, Portals).

Implement this step if:

• Swapper uses deposit-to-address model (Chainflip, NEAR Intents)
• Need to track order IDs or swap IDs between quote and execution
• Status polling requires data beyond transaction hash

Three places to modify:

a. packages/swapper/src/types.ts - Add to TradeQuoteStep:

export type TradeQuoteStep = {
  // ... existing fields
  [swapperName]Specific?: {
    depositAddress: string
    swapId: string | number
    memo?: string
    deadline?: string
    // ... other tracking fields
  }
}

b. packages/swapper/src/types.ts - Add to SwapperSpecificMetadata:

export type SwapperSpecificMetadata = {
  chainflipSwapId: number | undefined
  nearIntentsSpecific?: { ... }
  // Add your swapper:
  [swapperName]Specific?: {
    depositAddress: string
    swapId: string | number
    memo?: string
    deadline?: string
  }
  relayTransactionMetadata: RelayTransactionMetadata | undefined
  // ...
}

c. Populate in quote (get[SwapperName]TradeQuote.ts):

const tradeQuote: TradeQuote = {
  // ...
  steps: [{
    // ...
    [swapperName]Specific: {
      depositAddress: quoteResponse.depositAddress,
      swapId: quoteResponse.id,
      memo: quoteResponse.memo,
      deadline: quoteResponse.deadline
    }
  }]
}

d. Extract into swap (TWO places - BOTH required!):

Place 1: src/components/MultiHopTrade/components/TradeConfirm/hooks/useTradeButtonProps.tsx

// Around line 114-126