Tony D’Addeo
@deodad
questions about OP Stack re-orgs: - can unsafe blocks be re-orged by the sequencer? - if so, how often are unsafe blocks re-orged? - in practice how many confirmations before block become safe? - is there a way to view historical re-orgs? - (bonus) what's the best way to detect a re-oreg?
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Roberto Bayardo
@bayardo.eth
Yes, unsafe blocks can potentially be reorged, but most deployments of OP Stack (e.g. Base's) try REALLY REALLY hard to avoid this in order to allow a tx receipt to be treated as an effective tx confirmation. So reorgs are extremely unlikely. I don't think Base has ever had one.
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Tony D’Addeo
@deodad
yea this checks out, for my us case the difference between zero and non-zero is the important one my current assumption is wait for 6 blocks confirmation and assume zero
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Greg
@greg
any specific reasoning for 6 block confirmations or its an arbitrary number? kinda relevant to some stuff we're working on at ENS
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Brock
@runninyeti.eth
tl;dr on our thinking at /indexing if it helps: 1) OP reorgs effectively don't happen due to centralized sequencers 2) We typically assume a tx is "safe" after 1 confirmation as a result 3) Even if there is a reorg, it's practically going to be a reordering of txs within blocks vs txs being reverted (obviously not guaranteed though) -> in the vast majority of cases, landing a tx onchain means it will persist through reorgs 4) If there is a reorg due to L1 state, that's going to be muchhh deeper (can be minutes to days) Decent related read on how the OP team is thinking about reorgs for their interop plays: https://docs.optimism.io/stack/interop/reorg
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Tony D’Addeo
@deodad
very useful thanks does this sound right? unsafe blocks are unsafe because they aren't committed to L1. in practice the sequencers are centralized so unsafe blocks don't get re-orged. still wondering what the exceptions are... has there even been an Optimism or Base re-org due to anything other than an L1 re-org? how frequent are the L1 re-orgs?
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Brock
@runninyeti.eth
re: unsafe - yeah! In the L2 world, there's the L2 sequencing and the L1 sequencing that can both lead to reorgs. Practically, the L2 centralization minimizes it on that side, and the separation of concerns at the L1 minimizes it on that side Anecdotally, I haven't noticed any reorgs due to the L1. There are reorgs that happen semi-regularly at the L2 level, but, also anecdotally, I haven't seen any more than 1 block deep e.g. our system received a one block hash for this block via a websocket connection and then later received a new block hash (within ~300ms): https://basescan.org/block/27490668
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