focil

Ethereum co-founder Vitalik Buterin recently published a series of technical articles discussing the future roadmap of Ethereum. In the latest article, he focused on analyzing the potential centralization risks in the block building pipeline and proposed solutions such as expanding the FOCIL mechanism and introducing encrypted mempools to enhance the network's censorship resistance.According to the plan, Ethereum will launch the Glamsterdam upgrade in the first half of 2026, which will introduce the enshrined Proposer-Builder Separation (ePBS) mechanism. This mechanism allows block proposers to outsource block construction to a permissionless open market, reducing the centralization risk at the staking level. However, Buterin pointed out that while ePBS can prevent the concentration of block building rights among a few staking pools, the block construction itself may still become concentrated among a few high-tier participants due to specialization and maximizing MEV, leading to a new trend of centralization.To address this issue, Ethereum developers plan to simultaneously launch the FOCIL (Forward Obligatory Commitment to Inclusion Lists) mechanism in the Glamsterdam upgrade. The initial version will randomly select 16 witnesses and mandate that specific transactions must be included in the block; otherwise, the block will be rejected. Buterin stated that even if block construction is controlled by a single malicious entity, FOCIL can still ensure that transactions cannot be completely censored.Additionally, Buterin explored the possibility of expanding the scale of FOCIL ("big FOCIL") and introducing encrypted mempools to further mitigate the issues of information asymmetry and power concentration in the block building process. Recently, Buterin has been vocal about topics such as the quantum resistance roadmap, execution layer improvements, and block building mechanisms, indicating that the core Ethereum development team is conducting systematic design and risk assessment for the next phase of protocol upgrades.

Vitalik Buterin posted on the X platform, stating that there is an important synergy between the FOCIL mechanism and the account abstraction proposal Ethereum's EIP-8141 (based on 7701). EIP-8141 elevates smart accounts (including multi-signature, quantum-resistant signatures, key changes, Gas sponsorship, etc.) to "first-class citizens," meaning that operations from these accounts can be directly packaged as on-chain transactions without additional encapsulation.At the same time, privacy protocols can achieve a multi-tenant account model through the paymaster or 2D nonce mechanism, thereby gaining the same level of native support. FOCIL provides a censorship-resistant fast transaction inclusion mechanism. With the combination of both, various transactions, including smart wallet transactions, Gas sponsorship transactions, and privacy protocol transactions, can be included in blocks by one of the 17 roles (proposers or inclusions) randomly selected for each time slot.Vitalik stated that this design can ensure that transactions are almost guaranteed to be completed on-chain within 1-2 time slots in adversarial environments. In the current version, each FOCIL volume is approximately 8kB, which is relatively small, but there is a path for future expansion that could support most transactions in a block entering through the FOCIL channel. This architecture is similar in characteristics to the multi-parallel proposer (MCP) design, but differs in that FOCIL does not control the "last look" related to MEV, which is still allocated through the ePBS auction mechanism.Vitalik emphasized that even if 100% of block time slots are monopolized by adversarial parties through the proposer-builder separation (PBS) mechanism, refusing to connect to the public mempool or discriminating against specific applications, FOCIL can still ensure that all transactions receive fast inclusion. Although this design does not eliminate the centralization risk of the proposer role, it significantly weakens its power. Under the EIP-8141 framework, transactions from smart wallets or privacy protocols can be directly received by FOCIL inclusions through the public mempool without additional intermediaries or encapsulation processes.Vitalik concluded that Ethereum is accelerating the advancement of core architecture upgrades.

Ethereum researcher Thomas Thiery (also known as soispoke) proposed FOCIL as a core anti-censorship feature in the Hegota upgrade. Hegota is Ethereum's second major upgrade scheduled for the second half of 2026. FOCIL is a protocol layer mechanism that modifies Ethereum's fork choice rules to enforce the inclusion of any valid transaction in on-chain blocks within a limited time.The main goal of this proposal is to reduce Ethereum's reliance on centralized validators to mitigate the potential risk of large-scale transaction censorship in the future, thereby enhancing Ethereum's core value as a neutral, censorship-resistant blockchain. An Ethereum researcher stated, "Without FOCIL, the protocol would be vulnerable to large-scale censorship events. Ethereum should proactively design for long-term resilience rather than reactively respond to sudden censorship."

According to Christine Kim's summary of the 171st Ethereum Consensus Layer Core Developers Meeting (ACDC), the main topics discussed in this meeting included: retaining trustless payments as a component of the embedded proposer-builder separation (ePBS) in the Glamsterdam upgrade, while formally removing the Fork Choice Mandatory Inclusion List (FOCIL) feature. Additionally, the Fusaka upgrade successfully launched on the mainnet on December 3, and the subsequent blob parameter hard fork was smoothly activated on December 9, with the network operating stably.The meeting also discussed proposals such as EIP 7688, 8061, and 8080, and plans to start planning the Heka upgrade in January next year, while considering replacing its star names with those that meet the International Astronomical Union standards.