what does lulu verify do?
Re-derives every chain on disk and says what that does and does not prove. The check used to live in the test suite, where only the people who wrote it could run it, and a guarantee the person relying on it cannot exercise is a claim, not a guarantee.
how do you run it?
In the parser’s own words, re-derive every chain on disk and report what moved. Every flag this build accepts, on one line:
lulu verify [--ledger LEDGER] [--snapshot SNAPSHOT]
lulu verify ± every round in ./ledgerlulu verify --snapshot ROUND ± one round
how does it notice a file that was cut short?
Every round closes with a record saying how many calls it made and how they came out, hashed into the same chain as the answers. That is what makes a short file readable as short: a round somebody has cut lines off the end of has lost the only sentence that said how long it was, and lulu verify says so.
what does the check not reach?
Any round collected before the seal existed, because a file that never stated its length cannot be shown to be missing anything. What is printed at the end is the limit of the check, not a summary of how well it went, and the paragraph about a cut tail is printed for the rounds it is still true of and for no others.