> For the complete documentation index, see [llms.txt](https://docs.megaeth.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.megaeth.com/mega-evme/cookbook.md). # Cookbook Worked examples for common `mega-evme` tasks. ## Debug a Failing Transaction Replay a transaction from MegaETH mainnet with opcode-level tracing to find the revert reason. Replace `0xabc123...` with a real transaction hash: ```bash mega-evme replay 0xabc123... \ --rpc https://mainnet.megaeth.com/rpc \ --trace --tracer opcode \ --trace.opcode.enable-return-data \ --trace.output trace.json ``` Inspect `trace.json` for the opcode that triggered `REVERT`. The return data contains the revert reason (ABI-encoded). ## Compare Gas Usage Across Specs Run the same calldata against different specs to see how gas costs differ: ```bash # Under Rex3 — call WETH.balanceOf mega-evme tx \ --fork --rpc https://mainnet.megaeth.com/rpc \ --sender.balance 1ether \ --receiver 0x4200000000000000000000000000000000000006 \ --input 0x70a08231000000000000000000000000f39fd6e51aad88f6f4ce6ab8827279cfffb92266 \ --spec Rex3 # Under Rex4 mega-evme tx \ --fork --rpc https://mainnet.megaeth.com/rpc \ --sender.balance 1ether \ --receiver 0x4200000000000000000000000000000000000006 \ --input 0x70a08231000000000000000000000000f39fd6e51aad88f6f4ce6ab8827279cfffb92266 \ --spec Rex4 ``` Compare the `gasUsed` in the output to understand the impact of spec changes on your contract. ## Deploy and Interact in Two Steps Deploy a contract, capture the state, then call it: ```bash # Step 1: Deploy mega-evme run --create true 0x6080604052... \ --sender.balance 10ether \ --dump --dump.output post-deploy.json # Note the deployed contract address printed in the output. # Step 2: Call the deployed contract — replace 0xDeployedAddress with the printed address # and 0x06fdde03 with the selector you want to call mega-evme run 0x \ --prestate post-deploy.json \ --receiver 0xDeployedAddress \ --input 0x06fdde03 \ --dump ``` ## Test SALT Bucket Impact on Storage Gas Observe how storage gas costs scale with bucket capacity: ```bash # Minimum bucket (free storage gas) mega-evme run 0x60aa600055 \ --spec Rex3 \ --trace --tracer opcode # Large bucket (expensive storage gas) mega-evme run 0x60aa600055 \ --spec Rex3 \ --bucket-capacity 0:5000000 \ --trace --tracer opcode ``` Compare the `gasCost` of the `SSTORE` opcode in both traces. ## Fork and Patch Storage for Access Control Testing Override an access-control slot to test a protected function without needing the actual admin key. This example patches WETH's slot 0 (total supply) and reads it back with `totalSupply()`: ```bash mega-evme tx \ --fork --rpc https://mainnet.megaeth.com/rpc \ --sender.balance 1ether \ --receiver 0x4200000000000000000000000000000000000006 \ --storage "0x4200000000000000000000000000000000000006:0x0=0x0000000000000000000000000000000000000000000000000000000000000001" \ --input 0x18160ddd ``` The `--storage` flag sets the slot to `1` before execution, so `totalSupply()` returns `1` regardless of the live chain value. ## Replay With Modified Calldata Test what would happen if a transaction had been called with different arguments. Replace `0xabc123...` with a real transaction hash from MegaETH mainnet: ```bash mega-evme replay 0xabc123... \ --rpc https://mainnet.megaeth.com/rpc \ --override.input 0x70a08231000000000000000000000000f39fd6e51aad88f6f4ce6ab8827279cfffb92266 \ --trace --tracer call ``` ## Fund Multiple Accounts for Multi-Party Testing Set up balances for several participants in a single command: ```bash mega-evme tx \ --faucet 0xf39Fd6e51aad88F6F4ce6aB8827279cffFb92266+=100ether \ --faucet 0x70997970C51812dc3A010C7d01b50e0d17dc79C8+=50ether \ --faucet 0x3C44CdDdB6a900fa2b585dd299e03d12FA4293BC+=25ether \ --sender 0xf39Fd6e51aad88F6F4ce6aB8827279cffFb92266 \ --receiver 0x4200000000000000000000000000000000000006 \ --input 0x06fdde03 \ --dump --dump.output multi-party-state.json ``` ## Capture a State Diff See exactly which accounts and storage slots a transaction modifies. `WETH.deposit()` wraps ETH and updates the caller's balance mapping: ```bash mega-evme tx \ --fork --rpc https://mainnet.megaeth.com/rpc \ --sender.balance 1ether \ --receiver 0x4200000000000000000000000000000000000006 \ --input 0xd0e30db0 \ --value 1000000000000000 \ --trace --tracer pre-state \ --trace.prestate.diff-mode \ --trace.output diff.json ``` The `diff.json` file shows `pre` and `post` states for all touched accounts. ## Investigate Gas Detention Behavior When a transaction reads volatile data (block environment fields, oracle storage), gas detention caps the remaining compute gas. Call `HighPrecisionTimestamp.timestamp()` — it reads oracle storage, which triggers detention: ```bash mega-evme tx \ --fork --rpc https://mainnet.megaeth.com/rpc \ --sender.balance 1ether \ --receiver 0x6342000000000000000000000000000000000002 \ --input 0xb80777ea \ --spec Rex4 \ --trace --tracer opcode \ --trace.output detention-trace.json ``` Look for a sharp drop in `gas` remaining after the oracle `SLOAD` opcode. --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter: ``` GET https://docs.megaeth.com/mega-evme/cookbook.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.