Swap by reply on Farcaster and X

Mention @layerhop with "swap 10 USDC to SOL" in a cast or post and get a link to a prefilled swap. On Farcaster it opens as a Mini App with your Farcaster wallet. The bots never execute swaps.

Write a cast on Farcaster or a post on X that mentions LayerHop's account with a swap request:

Text

@layerhop swap 10 USDC to SOL

The bot replies with a link to a prefilled swap page at app.layerhop.com/swap. You check the live quote, change anything you like, connect your own wallet and sign. The bots never quote on your behalf, hold funds, sign or send anything: the reply is only a link.

What can I write?#

The parser (parseSwapCommand in @layerhop/shared) understands:

You write	It means
`swap 10 USDC to SOL`	10 USDC (on Base, which the reply says you can change) to SOL on Solana
`swap 100 USDC on Arbitrum to USDT on Polygon`	both chains named
`bridge 0.1 ETH from Arbitrum to Base`	a chain name as the destination coin: ETH on Base
`swap 0.5 SOL to USDC`	SOL names Solana, so USDC arrives on Solana too
`swap 0.1 ETH to USDC on Base`	a chain named only at the end applies to both sides
`buy $10 of SOL`, `buy SOL with 10 USDC`	buy with USDC
`25 usdc → sol`	no verb needed when the request is complete

Amounts: 10, 0.5, 1,000, 2.5k, $10 (dollars, only with a stablecoin). max, all or half get a question back: the bot never guesses an amount.
Tokens: symbols in any case, $SOL tickers, usd/dollars (USDC), ether, matic (POL), or a token address with its chain (to 0x4ed4…efed on base; a Solana mint implies Solana).
Chains: slug, name or id, plus eth/mainnet, arb, op, bnb/bsc, poly/matic, sol, avax. Coins that live on one chain (SOL, BNB, POL, AVAX, …) name their chain; ETH and stablecoins don't.
Ambiguity gets a question, not a guess: swap 10 USDC to ETH asks which chain ETH should arrive on. A misspelt chain (on bsae) is pointed out.
Chat that merely mentions an amount ("I sent 10 USDC to my friend") and send … to <address> get no reply.

How does the Farcaster Mini App work?#

Every prefilled swap link on app.layerhop.com/swap carries a Farcaster Mini App embed (fc:miniapp, plus the legacy fc:frame) with an image of the live quote and a Swap on LayerHop button. In a Farcaster client the button opens the page inside the client, and the page connects the client's own wallet (the EIP-1193 provider from the Mini App SDK). You still review and sign the swap. The manifest is at app.layerhop.com/.well-known/farcaster.json.

You can post such links yourself: any deep link to app.layerhop.com/swap?… unfurls the same way on Farcaster, and as an image of the quote on X, Telegram and Discord.

How is the Farcaster bot built?#

Neynar delivers casts that mention the bot to POST /v1/social/farcaster/webhook (cast.created). Each delivery is signed: X-Neynar-Signature is the HMAC-SHA512 (hex) of the raw body with the webhook secret, and unsigned or mis-signed requests get 401. The bot replies through Neynar's cast API with the swap link as an embed, once per cast (a retry is recognised), at most 5 replies per author and hour and FARCASTER_MAX_REPLIES_PER_DAY a day.

How is the X bot built?#

It polls the bot account's mentions (GET /2/users/{id}/mentions, app bearer token) every X_POLL_SECONDS and replies with POST /2/tweets using the account's OAuth 1.0a user tokens. Every mention read and every reply is recorded, so the monthly spend estimate survives restarts. It pauses for the month at X_MONTHLY_BUDGET_USD, posts at most X_MAX_REPLIES_PER_DAY replies and 3 per author a day, and answers each post once. X bills link posts at a much higher rate than plain posts, so keep the daily cap low.

Both bots are off unless their credentials are set; see the deployment guide in the repository (docs/DEPLOY.md) for the variables and the cost notes.