Execution

Simulate calls, replay transactions, and inspect block-level state changes.

The execution commands inspect what the EVM does with calls, transactions, and blocks.

Use these commands when you want to answer execution-client questions such as:

• what return data and gas estimate would this call produce?
• what call tree did this mined transaction execute?
• which accounts and storage slots changed while executing this block?

Simulate

Run an eth_call and eth_estimateGas against a selected block state.

Replay Tx

Replay one transaction with the debug call tracer.

State Diff

Trace a block and summarize changed accounts and storage slots.

Prerequisites

execution simulate uses the standard eth namespace:

reth node \
  --dev \
  --http \
  --http.api eth,net,web3 \
  --datadir ./alice

execution replay-tx and execution state-diff use debug tracing methods. Enable the debug namespace:

reth node \
  --dev \
  --http \
  --http.api eth,net,web3,debug \
  --datadir ./alice

Rex connects to the local execution RPC endpoint at http://127.0.0.1:8545 (localhost:8545) by default:

rex execution state-diff --block latest

Use the global --rpc <URL> flag to target a different endpoint.

Block Selectors

Execution commands that accept --block support:

• decimal block numbers such as 12345
• 0x-prefixed block numbers such as 0x3039
• 32-byte block hashes
• tags: latest, safe, finalized, and earliest

For block hashes, state-diff uses debug_traceBlockByHash. For number and tag selectors, it uses debug_traceBlockByNumber.