I built a TradingView-style backtester with AI. Here is the stack and the build prompt.

I wanted a replay and backtesting workflow I could customize, so I built one with AI coding tools. The starting stack: \- TradingView Lightweight Charts for the chart UI \- Public APIs for live data and Databento for futures history \- Python/FastAPI and DuckDB for a local implementation \- A replay engine that hides future candles and steps forward one bar at a time I put together a 4:30 tutorial showing the stack, my replay workflow, analytics and how I describe strategy rules to Claude. The full build prompt is in the video description: https://youtu.be/\_J51OuwtPWw The prompt also asks for commissions, slippage and a separate holdout period. Those need to be checked in the implementation; a good-looking equity curve alone doesn't prove a strategy works. Disclosure: I built JellyCharts, the app shown in the demo. For anyone who has built a replay engine: what was the hardest part to get right—data alignment, fills or lookahead bias?