Co-Founder and CEO of Taiko Labs, Daniel Wang, shared a post on the social platform X, commenting on the varying reliability of rollup implementations, suggesting that not all code should be viewed equally. He pointed out that a rollup might technically qualify as Stage 2 in terms of decentralization and functionality but still rely on new, untested code that has not yet faced real-world stress conditions.
As a result, Daniel Wang proposed an additional classification, suggesting the term “Battle Tested” be used to identify rollups that have demonstrated stability and resilience.
According to him, a rollup may be considered “Battle Tested” if it has been running on the Ethereum mainnet with its current configuration and codebase for more than six months, consistently securing over $100 million in total value locked (TVL), including at least $50 million in ETH and major stablecoins. Daniel Wang clarified that this status is not permanent—any upgrade would reset the evaluation period, requiring the rollup to re-establish its reliability under production conditions.
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This label is independent of @l2beat’s Stage model. A rollup can be Stage 2 without being BattleTested, or BattleTested without being Stage 2.
One is about decentralization. The other is about code maturity.
— Daniel Wang (@realdantaik) May 4, 2025
Daniel Wang also mentioned that the Ethereum Layer 2 project Taiko aims to reach Stage 2 and intends to adopt code that meets the “Battle Tested” criteria for future upgrades. He added that a separate Ethereum testbed rollup might be necessary to support this development strategy.
In response, Ethereum co-founder Vitalik Buterin remarked that achieving Stage 2 status is not the sole determinant of a rollup’s security; the reliability of the underlying proof system plays a crucial role as well. He proposed a simplified mathematical model to guide decisions on when transitioning to Stage 2 might be appropriate, based on several assumptions.
The model assumes each security council member has an independent 10% chance of failing, whether due to safety issues such as signing incorrect data or being compromised, or liveness issues such as failing to sign due to inaccessibility. The goal of the model is to minimize the overall risk of the protocol failing under these conditions. In the model, a Stage 0 security setup operates on a 4-out-of-7 multisig, while Stage 1 relies on a 6-out-of-8 structure.
Vitalik Buterin also acknowledged that this simplified approach does not account for potential shared vulnerabilities among council members—such as the risk of coordinated compromise or simultaneous coercion—which would reduce the real-world security of both Stage 0 and Stage 1 setups. Therefore, he suggested that transitioning to Stage 2 may be optimal earlier than the model initially suggests.
He also emphasized that the risk of proof system failure can be reduced by using a multisig arrangement that combines multiple independent proof systems.
Vitalik Buterin illustrated this concept with a chart where the X-axis represents the likelihood of the proof system failing, and the Y-axis reflects the probability of the entire protocol failing. As the reliability of the proof system improves, the ideal stage for protocol operation shifts progressively—from Stage 0 to Stage 1, and then to Stage 2. However, he noted that attempting to implement Stage 2 using a low-quality proof system carries the highest risk overall.
Here is a simplified mathematical model that shows when to move to stage 2.
Assumptions:
* Each security council member has an independent 10% chance of "breaking"
* we treat liveness failure [refusal to sign or keys inaccessible] and safety failure [signing a wrong thing or… pic.twitter.com/KM8EIZF9Io
— vitalik.eth (@VitalikButerin) May 5, 2025
Stage 2 Rollups Mark Peak Decentralization In Ethereum Layer 2, Removing Reliance On Centralized Control
In the context of Ethereum’s Layer 2 ecosystem, a Stage 2 rollup is regarded as the highest maturity level in terms of decentralization and trust minimization, based on criteria outlined in the L2BEAT framework. At this stage, the rollup functions entirely through smart contracts and cryptographic proofs, with no reliance on centralized actors for transaction validation or system oversight.
In order to reach this level, the rollup must demonstrate that it allows open participation in the verification process, meaning that any user can validate or dispute state transitions. It must also include effective on-chain mechanisms for resolving disputes, ensuring that errors in state updates can be transparently challenged and corrected. In addition, users must be able to withdraw their assets directly to Ethereum Layer 1 at any time, without needing permission or intervention from a centralized party.
Attaining Stage 2 reflects that the rollup has matured beyond its early-phase safeguards—sometimes referred to as “training wheels”—and now operates with a security and decentralization model that aligns closely with that of Ethereum’s base layer.
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