Supported Chains Overview

This page describes what Fusion supports today, not what the roadmap implies.

Supported chains

Chain	Chain ID	Family
Arbitrum Sepolia	421614	EVM
Base Sepolia	84532	EVM
Midnight Preprod	2147483647	Midnight

Supported routes

Route family	Notes
Arbitrum Sepolia <-> Base Sepolia	The primary public testnet corridor.
Midnight -> Arbitrum Sepolia	Uses source-lock attestation and session machinery.
Midnight -> Base Sepolia	Same as above.
Arbitrum Sepolia -> Midnight	Enabled by default via the shared route manifest.
Base Sepolia -> Midnight	Enabled by default via the shared route manifest.

Route support is driven by the canonical route-manifest.ts; operators can disable individual routes at runtime through the backend's DISABLED_ROUTES env-var override.

Midnight -> Midnight is not supported — same-chain Midnight routes are explicitly rejected.

On the roadmap

• Optimism, Celo, and other EVM L2s are on the near-term roadmap. Optimism Sepolia is already reserved in client types; runtime support for the rest is being wired up as each integration comes online.
• Non-EVM ecosystems — Solana and other non-EVM chain families — are further out on the roadmap. Each integration is scoped individually because address formats, wallet connectors, and settlement semantics vary by family, the same way Midnight did.

Why non-EVM chains need different handling

Non-EVM chains are not just "another EVM chain" — integrating one changes several parts of the flow:

• address width and canonical byte form
• hash-function choice (cross-family routes use sha256 rather than keccak256)
• source-lock flow (session-based rather than direct EVM lock)
• route direction rules and feature-flag gating
• operational dependencies (chain-specific sidecars, proof servers, indexers)

The current concrete example is the Midnight integration, which is why the reference docs treat Midnight as its own family rather than another row in the EVM chain table. The same pattern will apply to future non-EVM integrations.

How to discover support at runtime

Use:

• GET /api/chains
• GET /api/health

before enabling a route in UI or server-side routing logic.

The backend returns whether each chain is enabled and operational in the current environment, which is more trustworthy than a static frontend dropdown alone.

Related docs:

• What Is Fusion?
• Wallet App Integration
• Chains and Timelocks