Internal deployment, dated 2026-09-01/02. Sources: F4221 fill-mode taxonomy, F4292 contamination audit.
Before offering Fidelity Lab's backtest methodology to customers, we ran it against our own ~42-million-leg internal trading ledger. The audit found the ledger's "real_fill=1" flag was a typed literal written by the emitter on every tape-priced paper leg — every one of 12.3 million "clean real-fill" legs was actually priced off historical tape with a simulated fill, not a genuine venue-reported execution. A separate forward-paper check found roughly 95.8% of positive top-line results before the fix traced to lookahead contamination, caught by an 11-detector battery (fill-mode mislabeling, epoch-zero entry timestamps, settlement-clock field mismatches, and more) built specifically to keep a backtest PIT-faithful. We fixed the labeling (a `fill_mode` column: venue_fill vs tape_priced vs synthetic) and re-ran every verdict split by tier before trusting any of it — the same walk-forward, cost-netted, per-market-ruler discipline every Fidelity Lab backtest runs for a customer's own strategy.
Data and research only. Not investment advice, not a recommendation to buy or sell, and not an offer of any security, swap or event contract. TradeHouse is not a registered investment adviser, broker-dealer or exchange. Any backtested, hypothetical or historical results are shown for illustration, have limitations (including hindsight and no trading costs or slippage unless stated), and do not guarantee future results. Prediction markets and options carry risk of loss.