Ledger Line - a dark factory that proves its work

Ledger Line is a four-seat software factory built in BAND Desktop for the pocketful track: a wallet and payments app where money must never be created, destroyed or spent twice. Its unit of truth is a requirements ledger. For each stage, before any code exists, the lead seat turns every testable sentence of the spec into a numbered line, plus the invariants that must survive concurrency and retries and the requirements no sample check exercises. The auditor challenges the ledger first: 12 points in stage 1, 13 in stage 2. The builder hands off one work item at a time with a commit hash and an evidence block. The prover never reads product code to decide what to test: it builds a clean image with no network, runs black-box and browser tests for every ledger line, and fires concurrency storms five times each. The auditor reviews the same commit. An item ships only when both name the same hash. It caught real bad work. Stage 1: a crash on huge numbers and replays compared at 28 digits. Stage 2: a feed that silently showed only 50 payments, and a hold expiry clamped with floating-point seconds. A reset too slow on a laptop was measured in the container and fixed. It also failed honestly, and FACTORY.md documents both failures from the room log. Stage 1 deadlocked on a reply that was staged but never posted, so the stage-2 dispatch added a liveness rule. Stage 2 was cut short when an operator's helper agent stopped the seats, so neither stage has a final report. Result, in isolated mode: stage 2 claimed with 147/147 and 35/35, and stage-1 still claims stage 1. Acceptance took 18 and 28 minutes after each dispatch. The mandates are generic and never name the track.