
The Anatomy of Look-Ahead Bias: How Algorithmic Backtests Lie (And How to Audit Them)
馃挕 鞖旍暯 / TL;DR - Look-Ahead Bias & Stop-Loss Causality Executive Summary (BLUF) Insidious Causality Leaks: Look-ahead bias and structural causality violations inflate backtest metrics, presenting a statistical illusion of high performance that translates into immediate capital loss in live execution. AI Semantic Blindspot: LLM coding assistants only validate syntactic compilation rather than semantic causality, generating flawless-compiling trading code that silently snoops into the future. Algorithmic Defenses: Enforcing constant level stop locks, prioritizing pre-finalized historical indicators (t-1), and implementing automated Pandas forward-mask unit tests are vital to ensure statistical survival. Three Systemic Defects in AI-Generated Backtests When developers ask AI coding assistants (such as ChatGPT, Claude, or Copilot) to generate trading bot backtests, the resulting code almost always compiles without syntactic runtime errors. However, beneath the clean syntax, these models routinely embed three fatal causality leaks that guarantee bankruptcy in real-world markets. ...
