MISSING TOOTH FILLED IN: Optimism, the Ethereum layer-2 project , provides the technological foundation for some of the biggest names in blockchain, including the Coinbase exchange’s popular Base blockchain and Worldcoin’s World Chain, from OpenAI founder Sam Altman. But for years, blockchains that used Optimism’s technology were built according to a false underlying premise: that they “borrowed” Ethereum’s security apparatus. In reality, it wasn’t the case, because they lacked a crucial piece of functionality known as “fault proofs” – used to challenge actors suspected of malicious behavior. On Monday, that long-promised tech finally came to Optimism’s mainnet, CoinDesk’s Margaux Nijkerk reported Tuesday . “We literally deleted the entire system essentially, re-architected it, and rewrote the entire thing,” Karl Floersch, CEO of OP Labs, said in an interview with CoinDesk. “That was brutal, but absolutely the correct decision.” The achievement might blunt some of the project’s most truculent criticism; similar “proof” technology is used by all layer-2 rollup networks, including Optimism competitors like Arbitrum. Without fault proofs, users who deposited funds into Optimism needed to trust the rollup’s “security council” to return their funds – a system vulnerable to potential human error or bias. With fault proofs, users should only need to trust Ethereum’s security. For now, though, the Security Council will remain intact and could still intervene in the event that the fault-proof system goes down.