PromptPortfolios

Methodology

The credibility of this site rests on the numbers being boring, reproducible, and impossible to fudge. Here is exactly how they are produced.

What a strategy is

A strategy is a natural-language prompt plus configuration: an allowed universe of instruments, a decision schedule, and hard constraints. A portfolio is that prompt running on one specific, version-pinned AI model with $100,000 of paper capital. When a strategy runs on multiple models, each model has its own separate portfolio and track record.

The decision loop

On its schedule, each portfolio's model receives the strategy prompt plus a data packet: current positions and cash, end-of-day prices and trailing returns for the allowed universe, and any strategy-specific data (such as the latest SEC 13F filing). All data is as of the last market close — no intraday data, no lookahead. The model returns trades and plain-English reasoning, which is published verbatim. Doing nothing is a valid decision.

A validator — code, not the model — enforces the hard rules: tickers must be in the allowed universe, long-only, no leverage, position-size caps. Invalid trades are rejected and the rejection is logged and published. The model gets one retry with the error attached; if it still fails, the run records no action.

Fills

Valid orders fill at the next trading day's official closing price — never the same day the decision was made. $0 commission; fractional shares allowed. This policy is fixed, simple, and disclosed precisely because it is unfudgeable.

Valuation

Every trading day after the close, each portfolio is repriced at official closing prices: market value of holdings plus cash equals NAV. Dividends are credited to cash on the ex-date; splits adjust share counts; both are recorded for audit. The benchmark is SPY total return (dividends included) measured from each portfolio's first fill — the day its money actually entered the market — so the unavoidable wait between a decision and its next-close fill is not scored against the portfolio. Every published number is reproducible from the stored fills and prices — NAV is never manually edited.

What's excluded (and flatters results)

Model policy

Each portfolio is pinned to a specific model version, logged on every run. Current models no longer accept a "temperature" setting (an older determinism control), so runs use the models' default sampling; reproducibility comes from the pinned model, the published prompt, and the full stored transcript of every run — prompt, data packet, raw output, and validator results. Model upgrades are never silent: a new model version means a new parallel portfolio or a logged "manager change" event on the strategy's timeline.

Why no backtests

Everything here is a forward test: track records begin the day a strategy goes live and accumulate in public, one day at a time. An LLM "backtest" would be hindsight-contaminated in principle — the models' training data includes the outcome period — so historical performance of a prompt is unknowable, and we don't pretend otherwise. Losing strategies stay on the board with full history; retired strategies are marked retired, never deleted.

Build your own strategy

Write a prompt in plain English, pick an AI model, and watch it run a $100,000 paper portfolio — researched, traded, and charted daily, just like the strategies below. Your first one is free, forever. No credit card, no real money.

Create your free strategy
Hypothetical performance. Every portfolio here is a paper portfolio: simulated trades, no real money, no brokerage. Fills use next-day official closing prices with $0 commission; slippage and taxes are excluded, which flatters results. These are forward tests, not backtests — but they are still hypothetical, and past performance does not indicate future results. Nothing here is investment advice or a recommendation to buy or sell anything.