SDM PoC2 in op-reth — nonsense/opgas-reth-poc2-tracer

This branch introduces the Sequencer-Defined Metering feature - SDM, with the block-level warming policy.

op-reth tracks block-level warming during execution, turns the resulting refunds into a system SDM transaction, exposes those refunds on receipts, and adds a replay/debug toolchain so we can inspect the accounting on historical blocks.

Design doc

https://github.com/ethereum-optimism/design-docs/pull/361

Benchmarking

Here are the results in terms of gas savings for this PoC: https://www.notion.so/oplabs/SDM-Benchmarking-for-PoC-2-Block-Level-Warming-330f153ee16280d4b2effdf0b3b53eb7

Code overview

1) SDM transaction type

• rust/op-alloy/crates/consensus/src/sdm.rs
• Adds a system transaction type: 0x7D
• Defines:
  • SDMGasEntry { index, gas_refund }
  • SDMPayload { version, entries }
  • TxSdm, a synthetic tx carrying the payload
• The payload is just: “for tx index i, here is the refund it earned from earlier warming in the block.”

2) Inspector-based (tracer) refund accounting inside the EVM

• rust/alloy-op-evm/src/sdm/inspector.rs
• The EVM now tracks when accounts / storage slots were first warmed and who warmed them.
• Refund categories are explicit:
  • warm account: +2500
  • warm SLOAD: +2000
  • warm SSTORE: +2100
• Deposits warm state for later txs, but they do not claim refunds themselves. The system SDM tx also never claims refunds.

3) Payload building includes the SDM tx

• rust/op-reth/crates/payload/src/builder.rs