feat: add client.experimental_blockTag + chain.experimental_preconfirmationTime

[jxom]

Brings back 530f0f1 via a Client option (client.experimental_blockTag), and a chain.experimental_preconfirmationTime for chains that support preconfirmations (e.g. "Flashblocks").

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🦋 Changeset detected

Latest commit: dc54b78

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
viem	Minor

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Name	Status	Preview	Updated (UTC)
viem	❌ Failed (Inspect)		Jul 20, 2025 1:59pm

[github-actions]

size-limit report 📦

Path	Size	Loading time (3g)	Running time (snapdragon)	Total time
import * from 'viem' (esm)	70.96 KB (0%)	1.5 s (0%)	2.6 s (+33.84% 🔺)	4 s
const viem = require('viem') (cjs)	87.8 KB (0%)	1.8 s (0%)	3.7 s (+35.71% 🔺)	5.5 s
import { createClient, http } from 'viem'	4.62 KB (0%)	93 ms (0%)	172 ms (-49.15% 🔽)	264 ms
import * from 'viem/account-abstraction'	53.2 KB (0%)	1.1 s (0%)	1.1 s (-1.65% 🔽)	2.2 s
import * from 'viem/accounts'	82.47 KB (0%)	1.7 s (0%)	1.2 s (+36.22% 🔺)	2.8 s
import { privateKeyToAccount } from 'viem/accounts'	21.04 KB (0%)	421 ms (0%)	646 ms (+45.71% 🔺)	1.1 s
import { mnemonicToAccount } from 'viem/accounts'	27.34 KB (0%)	547 ms (0%)	657 ms (-5.21% 🔽)	1.3 s
import * from 'viem/actions'	55.71 KB (0%)	1.2 s (0%)	1.4 s (-19.91% 🔽)	2.5 s
import { getBlockNumber } from 'viem/actions'	318 B (0%)	10 ms (0%)	107 ms (+2232.9% 🔺)	117 ms
import * from 'viem/chains'	48.03 KB (0%)	961 ms (0%)	1.2 s (-47.9% 🔽)	2.1 s
import { mainnet } from 'viem/chains'	325 B (0%)	10 ms (0%)	5 ms (-4.52% 🔽)	15 ms
import * from 'viem/chains/utils'	1.08 KB (0%)	22 ms (0%)	34 ms (-1.52% 🔽)	55 ms
import * from 'viem/ens'	47.87 KB (0%)	958 ms (0%)	722 ms (-16.19% 🔽)	1.7 s
import { getEnsAvatar } from 'viem/ens'	24.06 KB (0%)	482 ms (0%)	693 ms (-12.04% 🔽)	1.2 s
import * from 'viem/siwe'	33.14 KB (0%)	663 ms (0%)	1.2 s (+12.63% 🔺)	1.8 s
import { verifySiweMessage } from 'viem/siwe'	32.05 KB (0%)	641 ms (0%)	1.5 s (+77.21% 🔺)	2.2 s