The credit union that runs end to end
on software we built.

The historical book arrived as fragments: one export of 3,680 records with the names stripped, two membership spreadsheets, the weekly benefits file, and the credit union's own paper till books. No dates of birth, no contact details, no documents, no transaction history for savings. Balances, and little else.

So we rebuilt it. Eight import pipelines, one per source, each deriving what it loaded: balances computed from ledger history rather than read from a field, instalments recovered from the payment schedules themselves, duplicates merged, and every row the arithmetic couldn't yet prove parked visibly, with a written note of what would resolve it. The book went live frozen: repayments open, outbound money locked until each member re-verified their identity, then opened one member at a time.

Then we let the arithmetic judge the result. Recomputing every loan's life day by day surfaced what no inspection could. The old model only calculated interest when a payment arrived, so a loan nobody paid simply froze; one had sat at the identical balance for thirteen and a half months. The rebuilt book reconciles against the credit union's own treasurer reports to within one pound, and its interest income decomposes to the penny with no unexplained remainder.

Most of the system as it exists today was designed and built in the final ninety days before launch, with the staff who use it: four out of five commits in the entire history land in that window. That pace comes from how we build. Every change passes an independent review and an automated test suite that grew from nothing to more than five thousand checks in the same ninety days. Inside those controls, AI agents write much of the code and we direct them. The map of the early prototype survived. The territory was replaced.

Going live on a real loan book meant rehearsing like it mattered: three full rehearsals on exact copies of the live book, identical figure for figure. Production ran one day after the final rehearsal, so every payment-tied figure had to match to the penny, and every calendar-tied figure had to move by exactly one day's interest. Both did. Mid-run, a safety check refused to write, and nobody overrode it: the cause was fixed, the untouched book restored from snapshot, the run repeated clean. The credit union then corrected its own migrated book by pressing six buttons in one legal order, each step verified, each step reversible.

And where rebuilding the truth changed what members owed, the change went in their favour: the family loan's pricing moved onto a daily basis that works out cheaper per year, applied retroactively.