# Glossary

Rome-specific and Solana terms used throughout this documentation.

## A

**ATA (Associated Token Account)** — A deterministic token account for a given wallet + mint pair on Solana. Derived from the wallet pubkey, token mint, and ATA program.

**Atomic Execution (VmAt)** — EVM transaction mode where the entire execution completes within a single Solana transaction. Default mode for most operations.

## B

**BN254** — An elliptic curve used for ZK proof verification. Rome supports ecAdd (0x06), ecMul (0x07), and ecPairing (0x08) precompiles.

**Borsh** — Binary Object Representation Serializer for Hashing. Solana's standard serialization format. Little-endian byte ordering.

## C

**Chain ID** — A unique identifier for each EVM environment on Rome. Each application gets its own chain ID.

**CPI (Cross-Program Invocation)** — One Solana program calling another within the same transaction. How Rome EVM contracts interact with Solana programs.

**Compute Units (CU)** — Solana's equivalent of Ethereum gas. Each transaction has a compute budget; operations consume CU.

## E

**ERC20SPL** — An ERC-20 wrapper contract that reads balances from the underlying SPL token account on Solana. No separate state — the ERC-20 IS the SPL token.

**ERC20SPLFactory** — A factory contract that deploys ERC20SPL wrappers for any SPL token mint.

## H

**Hercules** — The block indexer service. Monitors Rome EVM events on Solana and produces Ethereum-compatible block data.

**Holder Account** — An on-chain buffer (max 80 KB) that stores large EVM transactions exceeding Solana's 1,232-byte transaction limit.

## I

**Iterative Execution (VmIt)** — EVM transaction mode that splits execution across multiple Solana transactions, executing \~500 opcodes per step. Used for compute-intensive operations.

## L

**Lamports** — Smallest unit of SOL. 1 SOL = 10^9 lamports.

## M

**Meta-Hook Router** — Token-2022 Transfer Hook multiplexer. Sits in a mint's single hook slot and dispatches to up to 8 sub-hooks.

**Mollusk SVM** — Off-chain Solana VM emulator used by Rome Proxy for `eth_call` and gas estimation. Can execute arbitrary BPF programs.

## O

**Oracle Gateway** — Adapter contracts exposing Pyth and Switchboard price feeds through Chainlink's AggregatorV3Interface.

**OP-Geth** — Modified Go-Ethereum client providing full Ethereum RPC compatibility. Optional — used in OP-Geth deployment mode.

## P

**Payer** — A Solana keypair that signs and pays for Solana transactions on behalf of EVM users. Managed by the Proxy.

**PDA (Program Derived Address)** — A deterministic Solana address derived from seeds and a program ID. No private key — the program "owns" the PDA.

**Proxy** — The Rome JSON-RPC server (port 9090) that translates Ethereum API calls into Solana transactions.

## R

**RSOL** — The default gas token on Rome EVM chains (wrapped SOL as ERC-20).

**Rhea** — The mempool bridge that relays transactions from OP-Geth to Solana. Only used in OP-Geth mode.

**RheaTx** — A single EVM transaction on one rollup.

**RemusTx** — Multiple EVM transactions across rollups, executed atomically.

**RomulusTx** — EVM transactions + native Solana instructions, executed atomically.

**ResourceFactory** — SDK component that pools Solana keypairs and holder account indices for parallel transaction submission.

## S

**Single-State Mode** — Deployment mode where users connect directly to Rome Proxy. No OP-Geth layer.

**SPL Token** — Solana's standard token program. All fungible tokens on Solana (USDC, SOL, etc.) are SPL tokens.

**StateHolder** — An on-chain account that stores serialized VM state between iterative execution steps.

## T

**Token-2022** — Next-generation SPL token program with extensions (Transfer Hooks, Confidential Transfers, Permanent Delegates).

**Transfer Hook** — Token-2022 extension that invokes a program on every `transfer_checked` call.

**TxBuilder** — SDK component that builds Solana instructions from EVM transactions.


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