Facet Bluebird

There is no privileged entity that sequences transactions or produces blocks. This activity is permissionless and open to anyone.

Because the state of the system is based on transactions submitted on the underlying host chain and anyone can submit their transactions there it allows the users to circumvent censorship by interacting with the EOA inbox on the host chain directly.

The user initiates L2->L1 messages by submitting a regular transaction on this chain. When the block containing that transaction is settled, the message becomes available for processing on L1. The process of block finalization takes a challenge period of 7d to complete. The challenge period can be shortened if the block is proven by providing a ZK proof.

Facet does not designate a canonical bridge and allows multiple bridges to be deployed that use the same Rollup state for depositing and withdrawing assets. Each bridge has its own smart contract counterpart on the L2, meaning the same L1 tokens bridged through different bridges will result in different L2 token representations. The risk analysis presented in this page is based on an arbitrarily selected ETH bridge built on top of Rollup.sol that does not introduce additional trust assumptions. However, there can be multiple other bridges to Facet that introduce additional trust assumptions, such as the FacetEtherBridgeV6 (0x0000000000000b07ED001607f5263D85bf28Ce4C) fast bridge that relies on a permissioned EOA as operator for withdrawal processing.

Facet uses FCT as its native gas token, which is minted through L1 gas consumption rather than being pre-minted. FCT issuance is directly tied to the amount of L1 ETH burned to pay calldata gas in Ethereum transactions, calculated as: FCT minted = ETH burned for calldata × mint rate ETH burned for calldata = L1 base fee × (total L1 gas cost - 21,000) The system targets issuing ~78,300 FCT every 500 Facet blocks. If less than the target is minted in 500 blocks, the mint rate increases proportionally (up to a maximum 4x increase). If the target is reached in fewer than 500 blocks, the mint rate decreases proportionally (up to a maximum 75% decrease). The maximum supply of FCT is ~1.65B. Once 50% of the supply is minted, the per-period target (now ~78,300) will be halved. It will be halved again at 75%, then at 87.5%, and so forth. The period target and period length are selected so that halvings will occur approximately every 5,256,000 blocks. This mechanism is similar to standard OP Stack guaranteed gas markets, where L1 gas is burned to purchase L2 gas for deposits through an EIP-1559-style fee market. However, on Facet, gas purchased in this way accrues to the purchaser’s native balance on the L2, whereas in the OP Stack it can only be used for a single transaction. .