flow-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 is obtainable at block 137390146 and above, and not below. THAT IS A LIMIT ON WHAT CAN BE RECORDED, not on what is published here. A transaction already recorded carries its own execution and steps from it for good; the boundary says that a transaction below it cannot be recorded NOW, because the state a replay would have to start from is not reachable by the pipeline that records this chain. The sentence below is that pipeline's own record of what it measured.

Of the 2 transactions recorded here, 2 step at source level, which needs verified source and debug information for every contract a transaction ran, and none 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: “the access node this capture read (access.mainnet.nodes.onflow.org:9000) serves state only from its own spork's root, block 137390146, and refuses the block below it. That is the node's retention, an operational limit: earlier sporks are served only by their own nodes, so it is not where the chain's history begins”

Recordings on this chain are executed from the cadence-ast 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.

How each trace on this chain is checked, in the pipeline's own words: “each transaction is re-executed by the network's own FVM and compared with what the chain recorded (status, every event with its values, and the computation), and one that does not match is published as divergent, never as a trace of the chain. Its Cadence source is the contract code the execution read from chain state, so no third party supplies it, and a file that does not hash to that code is discarded”