EthereumJS on X: Builder flow in @ethereumjs/vm: runBlock(vm, { block, generate: true, }) No extra flag be…

📋 Thread 2 — Block-Level Access Lists.

Yesterday: gas got two dimensions.
Today: every block commits a list of *what state it touched*.

EIP-7928. The Glamsterdam EL headliner. 🧵

EthereumJS Verified account @EFJavaScript Aug 25

⛽ Thread 1 — the 21,000-gas myth.

A plain ETH transfer was always 21,000 gas.
On Amsterdam, that number still exists — and it will still brick wallets.

Here's why. 🧵
View quoted post on X

EthereumJS @EFJavaScript Aug 26

Replying to @EFJavaScript

Status quo (today):

Execute a block → txs run → state changes.

Which accounts were read? Which slots changed?
You discover that *during* execution — or by replaying traces.

Nothing in the header promises it upfront.

EthereumJS @EFJavaScript Aug 26

Replying to @EFJavaScript

Amsterdam adds a Block-Level Access List (BAL).

After the block runs, the VM records which accounts were accessed — balances, nonces, code, storage.

Beside the block body, not inside.
Header: blockAccessListHash.

eips.ethereum.org/EIPS/eip-7928

eips.ethereum.org EIP-7928: Block-Level Access Lists Enforced block access lists with state locations and post-transaction state diffs

EthereumJS @EFJavaScript Aug 26

Replying to @EFJavaScript

Why it matters:

Validators and builders can see state touch patterns *before* parallel execution work gets serious.

Glamsterdam pairs this with ePBS on the consensus layer.
EthereumJS covers the execution side — run it locally.

EthereumJS @EFJavaScript Aug 26

Replying to @EFJavaScript

Builder flow in @ethereumjs/vm:

runBlock(vm, {
block,
generate: true,
})

No extra flag beyond Amsterdam.
The VM accumulates accesses automatically while executing.

Replies

EthereumJS @EFJavaScript Aug 26

Replying to @EFJavaScript

Then read:

result.blockLevelAccessList

One plain ETH transfer → 4 accounts in the BAL on our example.

Header hash must match bal.hash().
Mismatch = invalid block.

EthereumJS @EFJavaScript Aug 26

Replying to @EFJavaScript

Validator flow:

runBlock(vm, {
block,
blockAccessList: balJson,
})

Pass the known list (JSON, RLP, or BlockLevelAccessList).
VM checks structure + hash, then compares against execution.

EthereumJS @EFJavaScript Aug 26

Replying to @EFJavaScript

Run it (Node 20+, any OS):

mkdir amsterdam-bal && cd amsterdam-bal
npm init -y
npm i @ethereumjs/vm@10.1.3 @ethereumjs/block@10.1.3 @ethereumjs/common@10.1.3 @ethereumjs/tx@10.1.3 @ethereumjs/util@10.1.3 tsx

EthereumJS @EFJavaScript Aug 26

Replying to @EFJavaScript

Copy runBlockBALGenerate.ts, then:

npx tsx runBlockBALGenerate.ts

github.com/ethereumjs/eth…

github.com ethereumjs-monorepo/packages/vm/examples/runBlockBALGenerate.ts at master · ethereumjs/ethereumjs... Ethereum L1 Protocol Stack and EVM in TypeScript. Contribute to ethereumjs/ethereumjs-monorepo development by creating an account on GitHub.

EthereumJS @EFJavaScript Aug 26

Replying to @EFJavaScript

The gotcha:

BAL is not per-tx — it is per *block*.
Use Hardfork.Amsterdam (full bundle), not EIP-7928 in isolation.

Peers exchange it separately (eth/71).
Your indexer cannot ignore the header hash.

EthereumJS @EFJavaScript Aug 26

Replying to @EFJavaScript

Full walkthrough + validator example:
runBlockBALValidate.ts

Docs:
github.com/ethereumjs/eth…

Experimental — not production.
Next: ETH transfer logs (EIP-7708). 🚀

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