David Data

YC S26

[David Data @davidhfdata]

https://t.co/v8OWtHgkI5

[David Data @davidhfdata]

Frontier LLMs are impressive at many things. Trading is not one of them.

We had Fable, GPT-5.5, Gemini 3.5 Pro, and Grok 4.5 each run a portfolio for ~1.6 years on a synthetic stock market they've never seen.

All of them lost money.

Think you can beat the benchmark? Try it 👇

[Alex Sima @sima_alexx]

Taking the leap is hard, but there's joy in the unknown.

@AdiKulkarni6 and I spent senior year pivoting through 4 ideas (including an AI hedge fund). Now we're building @davidhfdata — synthetic market data for superhuman AI trading.

Excited to join @ycombinator S26!

[Adi Kulkarni @AdiKulkarni6]

Superhuman AI traders won't be trained on the past. They'll be trained on every possible future.

That's what @sima_alexx and I are building at @davidhfdata.

Excited to join @ycombinator S26

[David Data @davidhfdata]

try it at https://t.co/FZPHZhADak

[David Data @davidhfdata]

Try it at https://t.co/9npN8ZzmBZ
Docs: https://t.co/DrpDYyba0l

[David Data @davidhfdata]

We spent $98,151.86 on stock markets that don't exist.

Because your trading agent already memorized the ones that do. 2008, 2020, every real crash…it's all in the training data.

David Data gives you synthetic markets your model has never seen.

[David Data @davidhfdata]

@AtifHussainOG 'Worked last week, dead this week' usually means the edge was fit to recent conditions, nothing structural. Real edges have a reason — an inefficiency or a risk premium someone pays you for. If you can't name why it should keep working, the backtest only described the past.

[David Data @davidhfdata]

@MatiasScalbi Serious robustness stack. The subtle gap: block bootstrap and walk-forward still resample the one history that happened. Run thousands of strategies and a few clear the funnel on luck alone. The hardest test is whether they hold on synthetic markets that never printed.

[David Data @davidhfdata]

@L1vsun The five forces are the easy half. The trap: those loadings are estimated on one history. Funds that last pressure-test whether they hold across regimes that never actually printed. Stable in-sample, fragile out-of-sample is how a hidden force turns out to be a hidden overfit.

[David Data @davidhfdata]

@ethanrkho @investingidiocy Carver's real point is statistical: your own track record is n=1. One price path, infinite ways to overfit to it. The shops that last think in distributions of outcomes, not the single timeline that happened to print...that's the whole job.

[David Data @davidhfdata]

Backtest on markets that never happened, agree or disagree?

[David Data @davidhfdata]

Real history is one roll of the dice. We let you roll it a million times.

[David Data @davidhfdata]

we want to help-max you if you're AI trading maxxing and don't have enough data maxxing or want to evaluate-max on future historically maxxed scenario maxing. We provide synthetic-maxxed financial-maxing data-maxxing API to the max (rate limit max) and we have AI cofounder Max.