Making Miniapps aware of a Farcaster client's supported chains

[jgresham]

Problem

There is not a way for a miniapps to know which chains are supported by a Farcaster client leading to miniapps not showing an accurate list of networks a user can use.

Example, a CB wallet (probably?) supports Base Sepolia and Warpcast currently does not. A miniapp

At the moment, Warpcast(soon to be Farcaster) supports chains Base, monad testnet, optimism, arbitrum, mainnet, polygon, unichain, Zora. Other clients likely will support a different chains.

Solutions

1. Add a supportedChainIds list to sdk.context.client
2. Create a separate simple npm package which has a lookup for sdk.context.client.clientId to supportedChainIds list.

supportedChainIds would not necessarily need to be an exhaustive list of chains, but at least a bare minimum.

[SamuelLHuber]

Even Warpcast depending on if the embedded wallet is used or your own is connected may support different chains.

Could you expand on use cases for 1,2? would love to learn how it would be used.

I can see it being useful in docs, not sure on programmatic checks? like something where on swaps one only going from chain to chain supported chains and more e.g. in balances too?

[darrylyeo]

Exposing a list of chain IDs in the SDK wouldn’t hurt, but this can quickly become stale if apps don’t bump their SDK package version in a timely manner.

My recommendation: have Warpcast announce Farcaster Wallet’s EIP-1193 object to the app using EIP-6963, then support the RPC methods wallet_addEthereumChain (EIP-3085) and wallet_switchEthereumChain (EIP-3326).

This lets apps “request” a particular chain, which Farcaster Wallet can accordingly accept or reject on the spot.

[darrylyeo]

In viem / wagmi, this makes it as easy as a switchChain call from the app side.

[SamuelLHuber]

related proposal of that API: #256

[deodad]

@darrylyeo Warpcast wallet does announce following 6963 and supports wallet_switchEthereumChain.

It doesn't support wallet_addEthereumChain though. I haven't looked too deep into but my gut reaction is this seems hard to get right. You can let the user add the chain and send transaction but to fully support a chain requires a lot more than this like indexing their token balances, NFTs, and activity history on that chain.

[jgresham]

I think we're good here then. It sounds like the app can know which chains are supported through this method. And it seems like the right way for other farcaster client wallets to follow.

[Ashoat]

Resolved in #256

[jgresham]

Resolved in #256

Excellent. Thanks!