Layer 2 chains that post claims to Ethereum and rely on challengers to catch false ones.
The idea: The rollup posts its claimed results to Ethereum. If a claim is wrong, anyone can challenge it during the dispute window by narrowing the disagreement down, step by step, to a single instruction, which Ethereum then executes itself to settle who was right. One honest, watchful challenger is enough.
Why it matters: Arbitrum, OP Mainnet and Base work this way.
On the map: fault proofs over L2 state roots
Rollups that post transaction data and state claims to Ethereum and rely on fault proofs: if someone posts a false claim, a challenger proves the error onchain during the dispute window[1].
Their security rests on Ethereum's state tries and hashes for the proofs, data availability, and at least one honest challenger, plus the L1 itself. Arbitrum, OP Mainnet and Base work this way[2].
If any of these breaks, this breaks too.
If this breaks, these break with it.
Nothing on the map depends on it: it is an end point, something people use directly.