Lookahead Bias as an Engineering Failure, Not a Statistical One

Lookahead bias enters through data-layer engineering decisions, not strategy logic, and can be eliminated by point-in-time access semantics.

Audit of ingestion, normalization, resampling and join paths; adversarial tests that attempt to extract future information through every access pattern.

Adversarial test suite in quant-market-data-replay — deliberate future-information extraction attempts fail against point-in-time reads.

Point-in-time safe reads enforced in the data layer prevent lookahead by construction. Consumers cannot opt out.

Consumer code can still misuse resampled windows above the data layer; the guarantee covers access, not strategy logic.