@anywalletkit/protocol-swap2-fynd

Fynd — Propeller Heads' DEX aggregator — as a same-chain swap2 provider for Any Wallet Kit. Exact-input swaps on Ethereum, Base, Arbitrum, BNB Chain, Polygon, Unichain and Robinhood Chain, routed over the pools Tycho indexes.

Install

npm install @anywalletkit/protocol-swap2-fynd @anywalletkit/core
# or: pnpm add @anywalletkit/protocol-swap2-fynd @anywalletkit/core  ·  yarn add @anywalletkit/protocol-swap2-fynd @anywalletkit/core

On npm: @anywalletkit/protocol-swap2-fynd, published from the release workflow with provenance.

Fynd License. Quotes, routes and transactions produced by Fynd are licensed under the Fynd License. In short:

• every swap built from a Fynd quote must settle through the Tycho router for its chain (the router registry), with its fees intact, and must not be re-routed around it;
• the router may take a platform fee and keeps positive slippage;
• if you earn revenue on such swaps (your own fees, spreads), Propeller Heads is owed a share of it, with reporting.

This module only ever sends the router transaction Fynd encoded. Read the license before you ship it.

What the module checks

Before anything is approved or signed, the encoded transaction is decoded and checked against the request:

• it targets the pinned TychoRouterV3 for that chain;
• the method is a plain singleSwap, sequentialSwap or splitSwap (no Permit2, no vault funds);
• it spends exactly the requested amount of the requested token, for the requested output token;
• it pays the user, not anyone else;
• the expected output and the minimum match the quote, and Fynd's fee breakdown adds up;
• it carries no client fee.

The router reverts below the minimum. With rpcUrls set, the exact transaction is also simulated: at quote time for native input (no allowance needed), and right before broadcast for every swap.

Why uniswap_v4_hooks is excluded by default. On 2026-10-24 every Ethereum route the hosted API built through Uniswap v4 hook pools was quoted about 0.6–1% above the market and reverted when simulated (4 of 4 native-input pairs, and USDT → USDC). The same pairs without those pools executed (8 of 8 across Ethereum, Base and Arbitrum). A route through an excluded family is refused even if the server returns one. The hosted API has neither its own simulation nor its price guard enabled, so these checks are the wallet's.

Configure

import { fyndProvider } from '@anywalletkit/protocol-swap2-fynd'

const fynd = fyndProvider({
  apiKey: process.env.FYND_API_KEY,      // hosted API; keep it on your server (remoteProvider)
  // selfHosted: { 8453: 'https://fynd-base.internal' },  // or your own `fynd serve` per chain
  rpcUrls: { 8453: ['https://base.example/rpc'] },        // optional: pre-broadcast simulation + receipts
})

Behind remoteProvider (the API key on your server), the app wires the router pins and the transaction check: remoteProvider({name: "fynd", baseUrl, ...fyndPins}). The engine then accepts only the Tycho router in FYND_CHAINS as call target and spender, and re-runs checkFyndTransaction on the client against the app's own request (input, tokens, recipient, minimum, no client fee) — a backend cannot point the swap anywhere else. Without the pins the stub gets no route.

| Option | Default | Meaning | |---|---|---| | apiKey | none | Hosted API key from Propeller Heads, sent as the raw Authorization header. | | baseUrl | https://fynd-api.propellerheads.xyz | Hosted API; requests go to {baseUrl}/v1/{chain}/quote. | | selfHosted | none | { chainId: url } — your own Fynd servers; requests go to {url}/v1/quote, without a key. | | rpcUrls | none | { chainId: [url…] } for simulation and receipts. | | defaultSlippageBps | 50 | Used when the caller passes none. | | quoteTtlMs | 30000 | Fynd prices at one block; the engine re-checks this before broadcast. | | excludeProtocols | ["uniswap_v4_hooks"] | Liquidity Fynd must not route through (names, or family prefixes ending in :). |

A chain is served when it has a self-hosted server or the hosted API key is set.

Not supported (yet)

• Exact-output swaps — Fynd only sells an exact input.
• A swap deadline. The router enforces a deadline only through a signed client-fee message; this module sends no client-fee parameters, so the on-chain protection is the minimum output.
• Integrator fees.

Apache-2.0 (this module's code). Fynd outputs: the Fynd License.