Consensus Evolution at Radix

Overview

Radix's consensus mechanism has evolved through multiple generations, each building on lessons learned:

eMunie (2013–2017)

Dan Hughes' earliest experiments with distributed ledger design. Explored various approaches to achieving consensus without a single chain.

Tempo (2017–2019)

Tempo was a DAG-based consensus mechanism that used logical clocks and gossip protocols. While innovative, Tempo had limitations in providing the strong finality guarantees needed for DeFi.

Cerberus (2020–present)

Cerberus replaced Tempo with a formal BFT protocol using braided cross-shard consensus. The whitepaper was published in 2020 and validated through the Hyperscale tests. In practice, the live Babylon mainnet runs Cerberus in a simplified unsharded form (a single shard group), a variant of the original HotStuff BFT; the fully sharded, multi-shard Cerberus design has not yet shipped.

Xi'an (2027 target)

Xi'an is Radix's sharded mainnet upgrade, intended to deliver the full Radix Engine sharding and linear scalability that has been Radix's goal since inception. Its original consensus design was the fully sharded Cerberus protocol, but the current production candidate (the community hyperscale-rs implementation, subject of the April 2026 Xi'an RFC) does not implement Cerberus, using a HotStuff-2–derived per-shard consensus instead – the later two-chain commit variant, distinct from the original HotStuff that Babylon runs today.