> For the complete documentation index, see [llms.txt](https://docs.rome.builders/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.rome.builders/resources/faq.md). # FAQ Frequently asked questions about Rome Protocol — is Rome a bridge or a rollup, Solidity compatibility, oracles, gas tokens, and Solana interop. ## General **What is Rome Protocol?** Rome is an EVM execution environment running natively inside the Solana runtime. Solidity contracts deploy on Solana with direct CPI access to all Solana programs. See [What is Rome?](/getting-started/what-is-rome.md) **Is Rome a bridge?** No. Rome EVM runs inside Solana's runtime as a first-class program. There's no message relay between separate chains. EVM state IS Solana state. **Is Rome a rollup?** Not the Rome EVM chains (Rubicon and Hadrian). A block indexer (Hercules) produces Ethereum-compatible blocks for wallets and explorers, but EVM execution happens inside a Solana program — not on a separate rollup chain. The [Rome ZK EVM](/rome-zk-evm/zk-evm.md) is a different product: operators run rollups that post batches to Solana and settle proved roots there. ## Development **Can I use my existing Solidity contracts?** Yes. Standard Solidity contracts deploy unchanged on Rome. If your contracts use Chainlink oracles, the Oracle Gateway provides the same `AggregatorV3Interface`. One thing is new for users, not for the contract: before a wrapper can move a wallet's tokens, that wallet grants the wrapper once (`approve_spl` on the Helper precompile). A contract that pulls a wrapper token with `transferFrom` needs each user to have done this. See [One-time grant per wallet](/core-concepts/token-interop.md#one-time-grant-per-wallet). **What Solidity version should I use?** 0.8.28 is recommended (matches the Rome Solidity SDK). Earlier versions work. **Can I use Hardhat? Foundry?** Both work. Configure your network with the Rome RPC URL and chain ID. See [Deploy Solidity](/developer-guides/deploy-solidity.md). **Can I use MetaMask?** Yes. Add Rome as a custom network in MetaMask with the appropriate RPC URL and chain ID. See [Quickstart](/getting-started/quickstart.md). **How much gas does a transaction use?** Ask the chain: use `eth_estimateGas`, as standard tooling does, and never hardcode 21,000. Most of a write's cost is creating Solana accounts, such as a never-used recipient, a new token account or a deployed contract, and the estimate includes it. Measured on Hadrian, a native transfer to a never-used address estimated 1,086,961 gas, while a transfer to an existing address estimated 21,000 and used 10,001. Rome charges the gas a transaction actually uses, which in these measurements was never more than the estimate. For calls into Solana programs, add a margin, as the SDK's 1.3x pad does, and set a gas ceiling if the estimate itself reverts. See [JSON-RPC Support](/reference/json-rpc.md). **How do I call Solana programs from Solidity?** Use the CPI precompile (`0xFF...08`) via the Rome Solidity SDK. See [Call Solana from EVM](/developer-guides/call-solana-from-evm.md). ## Performance **What's the transaction finality time?** A transaction is confirmed within about one Solana slot, a fraction of a second. That is confirmation on the Rome chain, not finality on Solana, which takes longer. **What's the compute budget?** \~1.4M compute units per atomic transaction. Operations exceeding this use iterative mode (split across multiple Solana transactions). See [Compute Budget](/core-concepts/compute-budget.md). ## Tokens **What gas token does Rome use?** Each chain chooses its own gas token — any SPL token, priced via Meteora pools. The public chains (Rubicon and Hadrian) use USDC as gas. On Hadrian it is test USDC; on [Rubicon](/networks/rubicon.md) it is real USDC. **How do ERC-20 tokens work on Rome?** ERC-20 tokens on Rome are wrappers over SPL tokens. For a wallet address, `balanceOf()` reads the SPL token account on Solana. For a contract address, the wrapper keeps the balance in its own ledger, because the contract's tokens sit in the wrapper's token account. `allowance()` is kept in EVM storage, apart from Solana delegates, and the wrapper moves a user's tokens as that user's SPL delegate after the one-time grant. See [Token Interop](/core-concepts/token-interop.md). **A Solana-side deposit or bridge transfer fails with "insufficient SOL," but my wallet is funded — why?** Rome's public testnet, Hadrian, settles on Solana Devnet, so your Solana wallet must be in the matching network mode (Rubicon settles on Solana mainnet). In Phantom, open Settings → Developer Settings → enable Testnet Mode with the network set to Devnet, then disconnect and reconnect both wallets and retry. If a token balance doesn't appear after a deposit, import the token into your wallet manually. ## Infrastructure **Do I need to run my own node?** No — connect to a public chain's RPC (see [Networks](/networks/networks.md)). Running your own chain means operating the Proxy and Hercules. **What databases does Rome need?** PostgreSQL, used by Hercules for block indexing and by the Proxy for block queries. **Can I run Rome locally?** Not as a ready-made local stack; there is no public one. Develop against a public chain — the [Quickstart](/getting-started/quickstart.md) deploys to Hadrian (testnet) in minutes. --- # 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. 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