Bolt: accelerating Ethereum through preconfirmations

We are excited to share our investment in Chainbound, an Ethereum company focused on bolt — a protocol for Ethereum preconfirmations and other proposer commitments. Bolt unlocks sub-second transaction experience for users and creates a new revenue source for Ethereum proposers. Bolt’s design focuses on trustless participation via restaked collateral, as well as compatibility with the existing mev-boost PBS pipeline. This provides safe, neutral and incentive-compatible introduction of new proposer commitments, pushing Ethereum’s innovation frontier forward.

Betting on preconfirmations 

With the core ideas of based rollups and their preconfirmations, Justin Drake’s original thesis behind preconfirmations has been farsighted: cross-L2 liquidity & user fragmentation issue will be resolved by shared sequencers, and Ethereum is the safest most neutral shared sequencer (aka based sequencing), as long as its UX is on par with other sequencers — which is precisely achieved via L1 preconfirmations for based rollup transactions. 

From our viewpoint, preconfirmations is a more basic Ethereum primitive, one that improves UX for users and increases proposers’ agency and expressivity, with additional revenue streams on top. In more detail:

L1 inclusion preconfirmations is the immediate wedge use case, offering instant confirmations for transfers, approvals and other non-contentious types of transactions. Inclusion preconfirmations will also strongly improve censorship resistance, by shifting inclusion responsibility from centralized block-builders to pseudonymous proposers.

State preconfirmations — commitments to a specific state transition — would drastically improve Ethereum's UX for all transactions. This will be possible in the future, provided a high level of proposer participation. State preconfirmations effectively change Ethereum's processing mode from discrete to continuous, moving closer to Solana’s architecture. In particular, this will impact block-building dynamics (cf. multi-block MEV) — we are actively exploring these effects and discussing with the community the best path forward.

Partial block building is an example of a more general proposal commitment: proposers could sell the top of their block ahead of time to state-preconfirmation provider, while allowing the rest of their block to be built in the just-in-time mev-boost auction. Or the other way around: they could sell the bottom of the block to an entity requiring hard inclusion guarantees, while letting the just-in-time auction decide the best top-of-block part.

To conclude, the key to our conviction lies not only in the UX improvements to L1 and L2s and the subsequent unlocks for based rollups, but more so in the strong network effects that such a two-sided preconfirmation marketplace typically exhibits, as well as in the unknown use cases of more general proposer commitment. We also strongly believe in delivering preconfirmations without sacrificing Ethereum’s decentralization, and we had been looking to support the right team to pull this vision forward.

Bolt’s inception and team

Our preseed portfolio company Chainbound was among the few initial participants of Ethereum  Sequencing and Preconfirmations calls, which have served as a coordination Shelling point for the researchers, builders and existing players. While the research and space were rapidly moving forward, our and Chainbound team’s visions converged on the same exciting opportunity of building preconfirmations protocol. As they refocused on bolt, we decided to double-down and led their seed round.

We are honored to collaborate with the Chainbound team in exploring the new design space of Ethereum proposers’ commitments. Francesco and Jonas have an excellent track-record of building Fiber, a low-latency private infrastructure for propagating transactions and blocks, currently employed by over 50% of Ethereum block builders. Since focusing on bolt, they have hired an amazing team of young talented engineers. While their product-first approach is centered around fast and iterative development (with the most recent achievement being the working testnet), they have also researched extensively the vast design space before landing on the current version, which we describe below.

Digging into bolt's architecture

To offer additional commitment services like preconfirmations, proposers need to register in a special onchain registry. Their participation needs to be economically bonded, either by the proposer directly restaking their stake, or capital providers delegating their tokens to the proposer via restaking protocol like Symbiotic or EigenLayer. This bond guarantees slashing in case of safety/liveness faults, incentivizing proposers to adhere to their commitments.

With the setup above, the happy path for users to preconfirm their transactions under 1 second (or obtain another proposer commitments) is depicted below. The new bolt-related entities are in blue, while the existing entities that need to be modified are in light-blue. Another remark is that bolt RPC is not strictly necessary, but will make wallet adoption much easier.

Step-by-step description of the flow:

1. User signs their transaction in their wallet, after which it is sent to bolt RPC endpoint;

2. The endpoint server chooses the next opted-in proposer in the look-ahead — the set of slots in the future (up to 32 in Ethereum) whose proposers are already known;

3. The commitment request is propagated to the chosen proposer;

4. The commitment receipt signed by the proposer is returned to the user — this commitment receipts can be used to slash faulty opted-in proposers in the future;

5. Proposer communicates to block-builders the block constraints they require to sign the header (e.g. for inclusion preconfirmations this could be “add these 10 transactions at the bottom of the block in no particular order”);

6. Builder sends the header and the proof that the constraint was satisfied (e.g. Merkle proof in case of inclusions).

Steps 5 and 6 above ensure that bolt is PBS-compatible — proposers can experiment with new types of commitments while preserving their MEV revenue-stream. The not-described slashing mechanics will be implemented through User submitting their commitment receipt to the challenger smart contract, after which the relevant proposer has some time to submit a proof that their commitment was executed correctly (in case User made a mistake).

The core design principles behind the system above are:

• Trustless: no new trusted entities are introduced — commitments are backed by economic assurances, not by trusted intermediaries;

• Permissionless: any proposer can opt-in to the protocol, and any user can request commitments from them — no central authority is needed;

• Compatible: bolt is designed to be compatible with the existing PBS pipeline — the only change required from a proposer is an additional sidecar;

• Flexible: bolt is designed to be versatile in handling different commitment types and use cases, with plans to expand the types of commitments it can support.

Accelerating Ethereum

Preconfirmations space is uniquely placed right at the juncture of private markets and Ethereum protocol development. The recent surge in the community and startup interest in preconfirmations led Ethereum researchers to reconsider some of the core design decisions, such as decreasing the block time to 2-4 seconds. This is how private markets effectively accelerate Ethereum's protocol development, and we at Cyber are proud to play our role in this, by backing bolt – the leading L1 solution for Ethereum preconfirmations and other proposer commitments .

The future is bright, so put on your sunglasses! 🕶️