Locate the last L1 block in an OP sequencing window
A derivation debugger can report a batch as missing one block too early. The sequencing window uses a half-open interval anchored on the epoch’s L1 origin.
Calculate the inclusive last height
Read the chain’s configured sequencing window size and the L1 origin of the epoch. With the deliberately small example below, block 103 is inside the range and 104 is outside it.
L1 origin E = 100
window size = 4
eligible range = [100, 104)
Missing data at block 102 is not enough to conclude that the epoch has no eligible batch. Traverse the remaining L1 data and apply the batch acceptance rules. The batch must also satisfy timestamp, parent and origin checks.
Separate the window from the channel timeout
The window limits which L1 data can supply a batch for an epoch. Channel timeout separately constrains the lifetime of a frame assembly. A channel can fail that rule even if an individual frame appears within the sequencing window. specs.optimism.io OP Stack specification