What a layer is here

A layer is an Orbit L3 chain with Elysium as its parent. It has its own chain id, its own RPC, its own explorer, and HYPE as its gas coin.

Batches and state claims are posted to Elysium, so anyone can replay them there and check what the layer said happened. Bridging HYPE on and off a layer goes through that layer's own rollup contracts: an Inbox and an Outbox on Elysium, which nothing and nobody can upgrade after creation (the rollup's owner is set to the burn address).

What the operator does

Each layer runs one Nitro process on infrastructure Demiurge operates. That process is the sequencer (it orders transactions and makes blocks), the batch poster (it posts batches to the SequencerInbox on Elysium) and the validator (it posts assertions about the layer's state). One operator, one sequencer, one validator per layer: there are no permissionless fraud proofs on day one.

What users keep regardless of the operator:

• Forced inclusion. A transaction can be pushed through the layer's delayed inbox on Elysium even if the sequencer ignores it.
• Replay. Everything needed to recompute the layer's state is on Elysium, in the batches and the delayed inbox.
• The Elysium rules. Deposits and withdrawals are defined by the layer's contracts on Elysium, not by the site.

HyperCore

The HyperCore read precompile is Elysium's own and a layer cannot reach it, today or after the ArbOS upgrade. An app that needs HyperCore data lives on Elysium and talks to the layer through the bridge.

The stack is OffchainLabs Nitro and the BoLD rollup contracts from nitro-contracts v3.2.0.