ethereum-mainnet

How far back this chain can be debugged

Stepping a transaction means re-executing it, and that needs the state the chain was in just before it ran. On this chain it was obtainable at every block this capture probed, down to block 0 — so no transaction published here sits below the boundary. The registry records a floor rather than full archive reach because a floor is what was MEASURED: the probe reached genesis and found state, which is a lower bound on the reach and not a promise about every block in between.

Of the 1 transaction recorded here, none steps at source level, which needs verified source and debug information for every contract a transaction ran, and 1 steps one VM instruction at a time. A debug tier belongs to each recording rather than to the chain, so this counts what was recorded and promises nothing about the next transaction.

How that boundary was established, in the pipeline's own words: “prestate was obtainable from 0 upward when this generation was captured, and not below it”

Recordings on this chain are executed from the evm format. Each transaction's page states the granularity its steps are reported at: source lines where the contract's source was resolved, otherwise the format's own units.