Layer 2

Execution moves, settlement remains

Layer-2 systems process activity away from Ethereum’s base execution and publish data or proofs back to it. This can lower user cost and increase capacity while keeping a route to base-layer settlement. But different rollups use different proof systems, data arrangements, upgrade controls, and withdrawal conditions.

Finality has stages

An optimistic rollup may accept a state first and leave a challenge window before it becomes final. A validity rollup proves a computation before the base layer accepts it, but still relies on circuits, data, and contracts. User interfaces often show a completed transaction long before every relevant form of finality has arrived.

Security is more than mathematical correctness

A proof can establish that a transition followed the specified rule. Admin keys may still upgrade contracts; a centralized sequencer may order or temporarily censor transactions; data availability may affect exit; an operator may capture fees and MEV. These are separate axes, not minor footnotes to one inherited label.

Temporary scaffolding needs an exit test

Central coordination can help a young system ship and recover from bugs. The question is how that power narrows over time and whether users retain an enforceable route out. A rollup becomes more chain-like not when its marketing changes, but when correctness, control, and value extraction can be examined independently.