a16z research team has unveiled a new concept called Strong Chain Quality (SCQ) — a mechanism where holding just 3% of the network's total stake guarantees 3% of the blockspace in every single block. Traditional Chain Quality (CQ) only ensures a probabilistic average over time; SCQ pushes granularity down to the internal space within each block.
From CQ to SCQ: A Granularity Shift
Blockchain security has long been measured by CQ: a coalition controlling X% of stake gets to propose X% of blocks over time. In early low-throughput chains, a block held only a few transactions, so who proposed a block effectively controlled its entire content. But modern chains can pack hundreds or thousands of transactions per block — CQ no longer captures fairness at the per-block level. SCQ demands that each block reflect the exact proportional stake, not just a statistical average.
The researchers model all participants as rational actors with unknown utilities. A protocol that lets a coalition accumulate excess rewards shifts incentives away from honest behavior, endangering security. SCQ prevents this by locking in proportional space allocation block by block.
Virtual Lanes: The Economic Abstraction
SCQ implies an abstraction called virtual lanes: every staking node holds a dedicated, fixed-ratio channel within each block. Think of it as a productive asset generating transaction fees and MEV. To acquire and maintain lanes, external entities must continuously accumulate the L1 token, creating sustained demand. The more value a lane can capture, the stronger the incentive to stake, reinforcing the token's value proposition.
This framework also enhances censorship resistance. SCQ does not promise that every honest transaction will be included — in periods of high demand, perfect censorship resistance is impossible. Instead, it gives each staking node a guaranteed inclusion budget within capacity constraints.
SCQ and Censorship Resistance: The Theoretical Link
Recent work emphasized instant censorship resistance — honest inputs must be included immediately, not eventually. SCQ extends this property under fixed block capacity. The MCP protocol (Multi-proposer Consensus Protocol) can be plugged into existing PBFT-style consensus to achieve both SCQ and censorship resistance. It allocates proposers' blockspace proportionally to their stake.
DAG-based BFT protocols offer a multi-mempool path, but standard implementations fall short of strict SCQ because a leader can still delay specific transactions. Tweaking these protocols can restore SCQ. Forced transaction inclusion mechanisms like EIP-7805 in Ethereum are also relevant.
Implementing SCQ: Two Extra Communication Rounds
Enabling SCQ on top of view-based BFT requires only two additional communication rounds and two small modifications. First round: each participant broadcasts its certified input. Second round: after receiving input from participant i, a node adds it to an inclusion list, then sends the list to the leader, committing to accept only blocks containing all listed inputs. The leader aggregates all inclusion lists into the block. Voting participants only approve blocks that include their own lists.
This sketch can be turned into a full protocol that satisfies SCQ after Global Stabilization Time (GST) while preserving liveness. Achieving SCQ before GST requires waiting for quorum in each round. Notably, SCQ does not specify the execution order of transactions within a block — that remains an open research area, such as ordering by priority fees. Alongside existing challenges like selfish mining, Monad tail forking resistance, and Ethereum LMD GHOST reorganizations, SCQ opens a new dimension for protocol design.