Monad REVM

monad-revm extends revm with Monad-specific execution semantics: gas model changes, repriced precompiles, MIP-3 memory accounting, MIP-8 page-ified storage accounting, Monad staking, and the Monad reserve-balance precompile.

EVM Compatibility

Component	Version
revm	v42.0.1
Supported Monad specs	`MonadEight`, `MonadNine`, `MonadTen`, `MonadNext`
Ethereum foundation	Prague for `MonadEight`; Osaka for `MonadNine`, `MonadTen`, and `MonadNext`
Default Monad spec	`MonadTen`

Hardfork schedule

Network	Chain ID	`MonadEight`	`MonadNine`	`MonadTen`	`MonadNext`
Mainnet	`143`	2025-11-20 14:30 UTC	2026-03-19 14:30 UTC	2026-09-02 14:30 UTC	Unscheduled
Testnet	`10143`	2025-11-19 14:30 UTC	2026-03-10 14:30 UTC	2026-08-12 14:30 UTC	Unscheduled

Use MonadHardfork::from_chain_and_timestamp(chain_id, timestamp) to resolve a known network. Mainnet and testnet timestamps at or after their respective MonadTen activations resolve to MonadTen; unknown chain IDs return None. Context::monad() deliberately defaults to MonadTen and does not perform schedule lookup.

What Monad Changes

Gas model

Monad uses a different cold-access model and charges transactions against their full gas limit.

Access Type	Ethereum	Monad
Cold storage (`SLOAD`)	2,100	8,100
Cold account (`BALANCE`, `EXTCODE`, `CALL`)	2,600	10,100
Warm access	100	100

The caller pays gas_limit * effective_gas_price, unused gas is not reimbursed, and the refund counter is zeroed. The block beneficiary receives the priority-fee component over the full gas limit. Unless explicitly overridden, transactions are capped at 30 million gas.

Repriced precompiles

Precompile	Address	Ethereum	Monad	Multiplier
`ecRecover`	`0x01`	3,000	6,000	2x
`ecAdd`	`0x06`	150	300	2x
`ecMul`	`0x07`	6,000	30,000	5x
`ecPairing`	`0x08`	45,000 + 34,000/pt	225,000 + 170,000/pt	5x
`blake2f`	`0x09`	rounds × 1	rounds × 2	2x
KZG point evaluation	`0x0a`	50,000	200,000	4x
P256VERIFY	`0x0100`	6,900 (Osaka)	6,900 (`MonadEight`+)	Enabled early

Bytecode and transaction rules

Rule	Ethereum	Monad
Runtime bytecode limit	24KB	128KB
Initcode limit	48KB	256KB
EIP-4844 blob tx	Supported	Rejected (`Eip4844NotSupported`)
EIP-7702 system authority	Supported	Rejected for the system address
EIP-7702 delegated `CREATE` / `CREATE2`	Supported	Rejected

MIP-3 memory model

Monad replaces Ethereum's quadratic memory expansion formula with a linear words / 2 cost on MonadNine and later. With the default memory_limit feature, memory is pooled across the call stack and the effective limit is min(configured_limit, 8 MiB). A lower configured limit remains in force; a higher configured value is retained so a transition back to MonadEight restores it. MonadEight uses REVM's configured limit and quadratic memory pricing.

Instruction tables, available and warm precompiles, and the effective memory limit are selected for every frame. Nested calls that cross Monad hardfork boundaries restore the parent frame's behavior on success, revert, error, and immediate precompile completion.

MIP-8 page-ified storage

MonadTen introduces MIP-8 page-level storage warming and gas accounting. Storage pages contain 128 consecutive words. Loading any word warms the page, and the first write plus net state growth are charged per page. MonadNine retains slot-level storage accounting; later hardforks inherit the MonadTen behavior.

Staking Precompile (`0x1000`)

Design overview

Monad staking uses three validator sets and two reward views to keep consensus transitions deterministic:

execution set: real-time set updated by delegation/undelegation.
consensus set: top validators selected at snapshot time.
snapshot set: previous consensus image used during boundary-period rewards.

Validator state is split into:

Execution state (stake, commission, accumulated_reward_per_token, flags, unclaimed rewards, keys/auth).
Epoch views (consensus / snapshot stake+commission) used by reward paths.

Delegator state tracks active stake, pending stake windows (delta_stake, next_delta_stake), reward cursor (accRewardPerToken), and linked-list pointers used by getDelegations / getDelegators pagination.

Epoch lifecycle

syscallReward(blockAuthor) distributes the per-block reward to the active validator pool.
syscallSnapshot() enters boundary mode, copies consensus to snapshot, rebuilds consensus from execution sorted by stake.
syscallOnEpochChange(newEpoch) finalizes the transition, updates epoch, and clears boundary mode.

blockAuthor -> validatorId resolution is via ValIdSecp mapping; rewards use consensus view outside boundary and snapshot view during boundary.

Reward accounting

Pool rewards use an accumulator model:

acc += reward * UNIT_BIAS / active_stake
Delegator rewards are computed from accumulator deltas.
Undelegation creates a WithdrawalRequest with an accumulator snapshot.
(epoch, validator) accumulator snapshots are reference-counted to support delayed withdrawals and epoch-window correctness.
ACTIVE_VALIDATOR_STAKE = 10_000_000 MON
MIN_AUTH_ADDRESS_STAKE = 100_000 MON
WITHDRAWAL_DELAY = 1 epoch
MIN_EXTERNAL_REWARD = 1e9, MAX_EXTERNAL_REWARD = 1e25
ACTIVE_VALSET_SIZE = 200

See implementation constants in crates/monad-revm/src/staking/constants.rs.

Staking API surface in `monad-revm`

The staking precompile is implemented for both read methods and state-mutating user/syscall methods. It is available at 0x1000.

Read methods

Method	Selector	Gas
`getEpoch()`	`0x757991a8`	`200`
`getProposerValId()`	`0xfbacb0be`	`100`
`getValidator(uint64)`	`0x2b6d639a`	`97,200`
`getDelegator(uint64,address)`	`0x573c1ce0`	`184,900`
`getWithdrawalRequest(uint64,address,uint8)`	`0x56fa2045`	`24,300`
`getConsensusValidatorSet(uint32)`	`0xfb29b729`	`814,000`
`getSnapshotValidatorSet(uint32)`	`0xde66a368`	`814,000`
`getExecutionValidatorSet(uint32)`	`0x7cb074df`	`814,000`
`getDelegations(address,uint64)`	`0x4fd66050`	`814,000`
`getDelegators(uint64,address)`	`0xa0843a26`	`814,000`

User write methods

Method	Selector	Gas	Payable
`addValidator(bytes,bytes,bytes)`	`0xf145204c`	`505,125`	Yes
`delegate(uint64)`	`0x84994fec`	`260,850`	Yes
`undelegate(uint64,uint256,uint8)`	`0x5cf41514`	`147,750`	No
`withdraw(uint64,uint8)`	`0xaed2ee73`	`68,675`	No
`compound(uint64)`	`0xb34fea67`	`289,325`	No
`claimRewards(uint64)`	`0xa76e2ca5`	`155,375`	No
`changeCommission(uint64,uint256)`	`0x9bdcc3c8`	`39,475`	No
`externalReward(uint64)`	`0xe4b3303b`	`66,575`	Yes

Syscalls

Method	Selector	Gas	Caller requirement
`syscallReward(address)`	`0x791bdcf3`	`100,000`	`SYSTEM_ADDRESS`
`syscallSnapshot()`	`0x157eeb21`	`500,000`	`SYSTEM_ADDRESS`
`syscallOnEpochChange(uint64)`	`0x1d4e9f02`	`50,000`	`SYSTEM_ADDRESS`

Execution semantics

Only direct CALL is accepted. DELEGATECALL, CALLCODE, and STATICCALL are rejected.
Unknown/short selectors route to fallback ("method not supported", 40k fallback cost).
Read path is dispatch-first for payability, matching C++ behavior (unknown selector fallback bypasses payability guard).
getDelegator is intentionally treated as a write selector in canonical execution because it settles delegator state via pull_delegator_up_to_date.

Important parity note

monad-revm tracks C++ staking behavior closely, but there are explicit implementation notes to keep in mind:

addValidator currently skips signature verification and uses simplified key-to-address derivation in write.rs. This is intentional in the current implementation and should be considered when writing integration tests.

How staking is implemented in `monad-revm`

Core modules:

crates/monad-revm/src/staking/mod.rs: top-level precompile dispatcher and read handlers.
crates/monad-revm/src/staking/write.rs: user write handlers, syscalls, and payability logic.
crates/monad-revm/src/staking/storage.rs: storage key derivation for staking namespaces.
crates/monad-revm/src/staking/types.rs: validator, delegator, withdrawal, and list types.
crates/monad-revm/src/staking/interface.rs: ABI definitions and selectors.
crates/monad-revm/src/staking/constants.rs: gas-independent staking constants.

Block lifecycle helpers:

crates/monad-revm/src/api/block.rs exposes apply_syscall_reward, apply_syscall_snapshot, apply_syscall_on_epoch_change, and apply_epoch_boundary.
syscallReward supports extended calldata (selector + blockAuthor + reward) for SystemCallEvm environments that cannot attach msg.value to system calls.

Reader integration path:

run_staking_with_reader(...) supports environments that do not expose full ContextTr, and is used by alloy-monad-evm integration.
Ordinary direct internal CALLs to the native staking address are supported. Top-level and internal calls routed through an EIP-7702 delegated address are rejected.

Reserve Balance Precompile (`0x1001`)

Activation

Active on MonadNine and above.
Exposes reserve-balance state during transaction execution.
The precompile is available at 0x1001 and returns None before MonadNine.

Solidity interface

interface IReserveBalance {
    function dippedIntoReserve() external returns (bool);
}

Selector: 0x3a61584e
Gas: 100

Semantics

Returns true when the current transaction state would violate Monad reserve-balance rules if execution ended at that point.
Intended for contracts that want to recover, branch, or revert early before transaction end.

Call restrictions

Only direct CALL is accepted.
STATICCALL, DELEGATECALL, and CALLCODE are rejected.
Ordinary direct internal CALLs to 0x1001 are supported. Top-level and internal calls routed through an EIP-7702 delegated address are rejected.
Calldata must be exactly the 4-byte selector.
Nonzero msg.value is rejected.

Error behavior matches the canonical Monad implementation:

Unknown or short selector: "method not supported"
Nonzero value: "value is nonzero"
Extra calldata beyond the selector: "input is invalid"

Chain context and tracker lifecycle

Canonical reserve-balance decisions require a populated MonadChainContext: the combined senders and authorities from the parent and grandparent blocks, current-block senders and authorization lists, the current transaction index, and the applicable maximum reserve balance. The default context is intentionally empty and is not sufficient to reproduce historical block execution. The default maximum reserve balance is 10 MON.

The standard transaction handler initializes and clears ReserveBalanceTracker at transaction boundaries. Embedders that execute a synthetic transaction as an enclosing call must set MonadJournalTr::set_preserve_reserve_balance_tracker(true) only for that synthetic execution and restore it to false before the next ordinary transaction. If the backing fork, journal state, or chain metadata is replaced while a tracker is preserved, call ReserveBalanceTracker::rebase with the replacement state and MonadChainContext; cached thresholds must not cross that boundary.

Installation

Add to your Cargo.toml:

[dependencies]
monad-revm = "0.7.0"
revm = "42.0.1"

To pin directly to the matching immutable Git release:

[dependencies]
monad-revm = { git = "https://github.com/category-labs/monad-revm", tag = "v0.7.0" }
revm = "42.0.1"

Usage

Basic example

use monad_revm::{monad_context_with_db, MonadBuilder};
use revm::{
    context::TxEnv,
    database::InMemoryDB,
    primitives::{Address, TxKind, U256},
    state::AccountInfo,
    ExecuteEvm,
};

let caller = Address::from([0x11; 20]);
let recipient = Address::from([0x22; 20]);

let mut db = InMemoryDB::default();
db.insert_account_info(
    caller,
    AccountInfo { balance: U256::from(1_000_000), ..Default::default() },
);

let context = monad_context_with_db(db);
let mut evm = context.build_monad();

let tx = TxEnv::builder()
    .caller(caller)
    .kind(TxKind::Call(recipient))
    .gas_limit(21_000)
    .gas_price(1)
    .build_fill();

let result = evm.transact(tx).expect("transaction should execute");

The same program is available as basic.rs.

With inspector

use monad_revm::{MonadBuilder, DefaultMonad};
use revm::{context::Context, inspector::NoOpInspector};

let ctx = Context::monad();
let mut evm = ctx.build_monad_with_inspector(NoOpInspector {});

With custom database

use monad_revm::{monad_context_with_db, MonadBuilder};

let db = MyCustomDatabase::new();
let context = monad_context_with_db(db);
let mut evm = context.build_monad();

Architecture

monad-revm/
├── crates/
│   └── monad-revm/
│       ├── Cargo.toml
│       ├── LICENSE
│       ├── examples/
│       │   └── basic.rs
│       └── src/
│           ├── lib.rs
│           ├── chain.rs
│           ├── cfg.rs
│           ├── evm.rs
│           ├── handler.rs
│           ├── instructions.rs
│           ├── journal.rs
│           ├── memory/
│           │   ├── mod.rs
│           │   └── opcodes.rs
│           ├── precompiles.rs
│           ├── reserve_balance/
│           │   ├── abi.rs
│           │   ├── error.rs
│           │   ├── interface.rs
│           │   ├── mod.rs
│           │   └── tracker.rs
│           ├── spec.rs
│           ├── api/
│           │   ├── block.rs
│           │   ├── builder.rs
│           │   ├── exec.rs
│           │   └── default_ctx.rs
│           └── staking/
│               ├── constants.rs
│               ├── mod.rs
│               ├── write.rs
│               ├── abi.rs
│               ├── interface.rs
│               ├── storage.rs
│               └── types.rs
├── CHANGELOG.md
├── LICENSE
├── README.md
└── Cargo.toml

Feature flags

std: Enable standard-library support for monad-revm, revm, and alloy-sol-types (default). With default-features = false, monad-revm is no_std and uses alloc.
serde: Enable serialization for MonadHardfork and forward serde support to revm.
memory_limit: Enable pooled memory accounting and MonadNine's 8 MiB protocol cap (default). MIP-3 linear pricing remains active when this feature is disabled, but the cap is not enforced.
optional_balance_check, optional_block_gas_limit, optional_no_base_fee: Forward the matching optional execution controls to revm.
c-kzg, secp256k1, portable, blst: Forward the matching cryptography/portability features to revm.
dev: Enable development-oriented optional execution controls used by tests and local integrations.

Integration layers

alloy-monad-evm: Alloy Evm / EvmFactory wrapper over monad-revm.
Foundry Monad integration: Forge, Anvil, Cast, and Chisel support.

Release coordination

monad-revm, alloy-monad-evm, and Foundry's Monad integration must move together when porting to a new upstream Foundry/revm/alloy stack. Keep downstream consumers pinned to matching integration refs during a port, then update them to the merged commits or immutable release tags before retiring temporary integration refs.

References

License

monad-revm is licensed under the MIT License.

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in these crates by you, shall be licensed as above, without any additional terms or conditions.

monad-revm 0.7.0