In-depth essays · #4 / 50 · L2 Rollups, Federations & Interoperability

What L2BEAT Stages 0, 1, and 2 Really Mean: Taking Off the Rollup Training Wheels

The objective framework that separates team-controlled chains from trustless rollups

Click on any rollup district in Ethereum City and you will see a tag reading ‘L2BEAT Stage 0’ or ‘Stage 1’. Proposed by Vitalik Buterin and maintained by the independent watchdog L2BEAT, the Stages framework measures how far a rollup has gone in removing human ‘training wheels’ and relying purely on cryptography and Ethereum L1.

1. Why Rollups Start with Training Wheels

In theory, a rollup protects user funds solely through L1 smart contracts and cryptographic proofs. In practice, complex proof systems can harbor bugs early in their life. Most teams therefore launch with multisig upgrade keys or permissioned challengers so they can patch vulnerabilities quickly.

If a team keeps unconditional upgrade keys forever, however, users are trusting a handful of signers rather than Ethereum. The Stages framework gives citizens a clear yardstick for how much operator trust remains.

2. Stage 0 (Full Training Wheels): On-Chain Data, Operator Control

A Stage 0 rollup posts its transaction data to Ethereum L1 and runs open-source state transition logic, but either lacks a working, permissionless proof system or allows an operator multisig to upgrade contracts without a long exit window or independent Security Council.

Importantly, a chain can also move backward: Scroll reached Stage 1 in April 2025, but when its independent Security Council was replaced by a team-controlled multisig in June 2026, L2BEAT downgraded it back to Stage 0.

3. Stage 1 (Limited Training Wheels): Permissionless Proofs and a Security Council

Reaching Stage 1 requires a live, functional proof system where any external actor with sufficient bond can challenge an invalid state root, plus an L1 escape hatch that lets users force-include transactions or withdraw funds if the sequencer censors them.

Any instant upgrade path must be guarded by a diverse Security Council of at least eight members (with a 75% threshold and strong external representation), or else give users at least seven days to exit before code changes take effect. Arbitrum One, OP Mainnet, Base, Unichain, and Ink all hold Stage 1 status.

4. Stage 2 (No Training Wheels): Code and Math Alone

At Stage 2, even the Security Council cannot make arbitrary upgrades—it may only intervene in response to provable on-chain soundness bugs, and normal upgrades must grant users a 30-day exit window. Checking the L2BEAT Stage badge in Ethereum City lets you see at a glance how close each district is to that trustless ideal.

Related districts in the city

Related glossary terms

This essay is an explainer written to help you read the city; it is not investment advice. Facts on this page are as of 2026-10 and may change. If you spot a mistake, please tell us through the contact page.