Chain level configuration of polling interval

[coffeexcoin]

Viem currently has a default polling interval on the client of 4 seconds (typically used in things like waitForTransactionReceipt or watchEvent.

I would like to propose a new field on chain definitions of blockTime to define the standard or average block interval for the chain. This setting could help inform the client of an ideal default polling interval - while 4s polling is great for ethereum, fast block L2s such as zksync (1 second), base (2s) arb stack (250ms) realistically need a shorter polling time for optimal UX.

Many developers are either building on many chains or on a specific L2, and may not think to adjust polling intervals, leading to the appearance of suboptimal performance or a "slow chain" when in fact the client is just waiting much longer than necessary to check for a transaction receipt.

Default for polling interval should be something along the lines of chain.blockTime ? chain.blockTime / 3 : 4000 to preserve existing behavior for chains where the time is not defined.

[imjameshall]

Big agree here. Having the flexibility here would be a win for all.

[jxom]

I am happy to accept a PR to add this.

[jxom]

Nevermind, I started: #3702.

[jamesonnuss]

Co-signing this. Having blockTime at the chain level would reduce the need for per-app overrides and help ensure consistent UX across projects. It also makes Viem more future proof as faster chains emerge. Better defaults, less config.