# Based Preconfirmations with MR-MEV-Boost by Lin Oshitani | Devcon SEA

- Speakers: [Lin Oshitani](https://streameth.org/speakers/lin-oshitani)
- Channel: [Devcon](https://streameth.org/devcon)
- Date: 2025-10-07
- Duration: 06:17
- Watch: https://streameth.org/watch/yt-fo2xDLSst_M
- YouTube: https://www.youtube.com/watch?v=fo2xDLSst_M

## Description

In this talk, we will analyze a simple strawman setup of based preconfirmations to highlight its challenges, such as supply chain centralization, the lack of pricing mechanisms, and latency/spam races. We will then introduce MR-MEV-Boost, a preconfirmation solution that runs multiple rounds of MEV-Boost auctions within a single slot. This solution addresses the mentioned challenges by preconfirming batches instead of individual transactions and better integrating with the L1 PBS pipeline.

Speaker(s): Lin Oshitani
Skill level: Intermediate
Track: Cryptoeconomics
Keywords: Rollups, User Experience, Mechanism design, sequencer, based, preconfs, pre-confirmations

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## Transcript

[Music] okay hello everyone um today I'm going to talk about basb confirmation with Mr M boost I'm Leno shitani from nethermind research okay so most rollups let's talk about most rollups today so most rollups today build their blocks using centralized sequencer so users send their transaction to centralized sequencer the L2 transactions the centralized sequencer will sequence the L2 transactions and eventually construct these L2 blocks submit it to the L1 block building Pipeline and then the L1 block block will constru include these L2 blocks and centralized sequencer are nice they can provide pre- confirmations and pre-c confirmations what are pre-c confirmations basically users for example user trans submits their transaction C to the centralized sequencer the centralized sequencer will return a precom which will say I will promise to include your transaction C at the third position of the block after transaction a and transaction B and then some time passes and then the central secer will actually like submit the L2 block but the thing here is that sprom will happen way ahead of time where before the L2 block is actually submitted to L1 so it provides good ux so centralized sequence are nice they can provide facts to X we have PE comps but however they're centralized so big question here is how do we decentralize so one idea here is what if we move the SE sequencer role entirely and this bring us to base base rollups so base rollups idea is to use the L1 block BLM pipeline to sequence not only the L1 transactions but also the L2 transactions so the user submit the transactions not only L1 but also the L2 and then the L1 block will and pipeline will sequence not only the L1 but also the L2 blocks so let's expand this L1 block pipeline part so this is like what the L1 block Lo pipeline looks like right now the user will submit the trans action and then there will going to be Builders who are going to collect these one transactions and then they're going to construct blocks and then there's going to be many Builders and then they're going to be many blocks and then each are going to submit a bid to the proposer the proposer is going to select the most profitable block and then propose it so the idea of Bas scups is that let's use this same pipeline that was used for the L1 which is used in blue here also for the L2 transactions which is using the red arrow here and BAS are great they inherit the o1 censorship resistance and liveness because there is no like external entity other than the and we only have the L1 actors that we already have right now and it also enables L1 composability because these L1 Builders they will have full sequencing rights over the L1 and the L2 so they can act basically as a shared sequencer between the L1 and the L2 providing composability guarantees but there's a problem which is base rollups are slow because there is no pre-c confirmations here so to the address this problem there is BAS pre- confirmations so base pre confirmations idea is this let's let the L1 proposer opt in to provide pre-confirmation during their slot so like the user can directly send their L2 transactions to the L1 proposer the L1 proposer can directly respond with a pre-confirmation and then later on the o1 Block building pipeline runs and then the proposer will ensure that these L2 blocks are included in the L1 blocks that they propose so one observation here is that providing pre confirmation requires sophistication because like the the proposer here they have to have some API or so some like RPC endpoint to provide the and you also need to run the L2 full nodes to actually like sequence these L2 blocks so they would probably want to delegate and the they will want to delegate what we call gateways so that idea of gateways is this proposer can delegate their pre-con duties to gateways ahead of their slot so the proposer can say hey this is my Gateway please send your pre-con request not to me but to this Gateway and the Gateway will be responsible for responding with pre-confirmation then eventually the Gateway will sequence s to blocks submit the proposer proposer will include it in their L1 blocks so gateways are nice but they have some problems which is first the inherent of L1 sensorship resistance and liveness is degraded because now you have this Gateway entity that didn't exist in the block Bing pipeline that is now sequencing Z2 transactions and now L1 composability is also made more complicated because you no longer have an entity that's sequencing both L1 and the L2 because the Gateway is sequencing L2 the Builder is sequencing L1 so the question here is can we introduce base pre confirmation while retaining the good properties of Base rollups and here comes our proposal which is called Mr Mev boost so it's for multi-round Mev boost and the idea is this so let's split the slots into multiple Subs slots AKA rounds and in each round let's run a m boost auction to pre-confirmation thing many times during the thought so instead of running it once in the 12C duration run it every 3 seconds for example and this uh pipeline is nice because there is no additional entity added to the pipeline so there is no Gateway here and as a result we inherit the1 sensor resistance and liveness much better because there's no additional choke point to the system and also enables L1 composability because the L1 Builder now is like sequencing both L1 and L2 or they're like pre-confirmation