Chains and Timelocks

This page is a snapshot of the current values Fusion uses.

It intentionally calls out a real implementation detail:

there is more than one timelock layer today, and those layers are not identical.

Chain registry

The backend chain registry currently includes:

Chain	Chain ID	Family	Block time	Finality time	Hash function	Native symbol
Arbitrum Sepolia	421614	evm	0.25s	60s	keccak256	ETH
Base Sepolia	84532	evm	2s	60s	keccak256	ETH
Midnight Preprod	2147483647	midnight	6s	18s	sha256	DUST

Hash-function policy

The backend helper logic currently resolves hash function like this:

Route	Hash function
Same-family, non-shielded EVM route	chain-native behavior, which is keccak256 for the EVM chains in the registry
Cross-family route	sha256
Shielded route on any family	sha256

This is why the HTLC contracts expose both standard creation methods and _SHA256 variants.

Timelock layer 1: backend route policy

The backend has a route-aware timelock helper with these values:

Route	Source seconds	Destination seconds
EVM -> EVM	2700	900
EVM -> Midnight	2700	900
Midnight -> EVM	2700	900
Midnight -> Midnight	3600	1200

The backend uses this layer for route guidance such as sourceLockRequirements in the HTLC params response.

Timelock layer 2: EVM HTLC contract constants

The HTLCAtomicSwap contract also hardcodes:

Contract constant	Value
SOURCE_CHAIN_TIMEOUT	2700 seconds
DESTINATION_CHAIN_TIMEOUT	900 seconds

Those values are the current EVM contract defaults for HTLC creation.

Why this matters

For routes that touch EVM, these two layers intentionally share the same 45 minute source / 15 minute destination floor. That gives local shielded settlement proof generation enough time to complete before the destination HTLC becomes refundable.

The safest way to read this today is:

• the backend route policy expresses the coordinator's intended timing budget per route family
• the EVM HTLC contract constants express the on-chain timeout defaults enforced by the Solidity implementation
• backend startup validates the deployed EVM HTLC contracts expose at least these timeout values before accepting swaps

If you are integrating or operating Fusion, verify the deployed contract addresses before treating any timeout table as authoritative.

Practical advice

• Use backend discovery and route APIs for runtime guidance.
• Read the current contract if you need exact EVM timeout behavior.
• Reconcile timing assumptions before treating a route as production-ready.

Chain-family notes

EVM family

• uses 20-byte addresses
• uses keccak256 by default for same-family routes
• currently covers Arbitrum Sepolia and Base Sepolia as the live public corridor

Midnight family

• uses 32-byte canonical hex addresses
• uses sha256
• requires extra operational services (sidecar, proof server, indexer)
• exposes NIGHT as the live swap asset and keeps DUST as the gas/resource token

Related docs

• Supported Chains Overview
• Standard vs Shielded Routes
• Atomic Settlement Guarantee