The BuildIT Blog Field notes on validation Twenty essays

Backtests,
honestly.

Plain-language essays on why strategy claims fail, what a backtest can actually prove, and the checks that separate a real edge from a well-dressed accident.

No signals No promises No affiliate links

All essays — newest first
Validation3 Nov 20266 min read

Why Most Backtests Lie — and the 7 Checks That Catch Them

A beautiful backtest is the easiest thing in trading to fake, usually by accident. The seven ways backtests mislead, and the check that catches each one.

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Method3 Nov 20267 min read

Walk-Forward Testing, Explained Honestly

Two different things travel under the name “walk-forward”. Know which one you are actually getting — period stability, or purged and embargoed training.

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Markets3 Nov 20266 min read

AI Trading Bots in 2026: Real Returns vs Advertised Claims

The dashboards all glow green. Here is what independent checks actually measured, and the five questions that separate a real record from marketing.

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Due diligence3 Nov 20265 min read

Before You Trust a Strategy: How to Audit Someone Else’s Backtest in 10 Minutes

Four questions expose most weak backtests in minutes: trial count, costs, sample span, and what chose the parameters. Plus the baseline test every claim must pass.

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Execution3 Nov 20265 min read

Backtest vs Live: Why Execution Friction Kills Good-Looking Strategies

Your strategy’s logic was never the problem. Latency, slippage and costs are the gap between a beautiful backtest and a losing live account — and the gap is measurable.

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Validation3 Nov 20267 min read

PBO, Explained in Plain English: The Probability Your Best Backtest Is a Fluke

You tested 8 strategies and one looks brilliant. PBO asks the question most backtests never face: among everything you tried, how likely is the winner just the luckiest loser?

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Statistics3 Nov 20266 min read

Why a 70% Win Rate Over 20 Trades Means Nothing

70% sounds like an edge. Over 20 trades, it is statistically indistinguishable from a coin flip. The Wilson interval shows why — with the numbers worked out.

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Baselines3 Nov 20266 min read

Beat Nothing First: The Baseline Test Every Trading Model Must Pass

Before a model earns your money, it must beat doing nothing. The always-bullish and no-change baselines are the humblest — and most skipped — test in trading.

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Validation3 Nov 20267 min read

MinTRL: How Long a Track Record Do You Actually Need?

A Sharpe ratio of 2.0 on 18 months of data proves almost nothing. Minimum Track Record Length turns “impressive Sharpe” into “how many years would this take to believe” — with the numbers.

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Due diligence3 Nov 20267 min read

How to Audit a Vendor’s Backtest Before You Pay a Single Rupee

You are not the one who built the strategy — you are the one being asked to pay for it. That makes you the auditor. Here is the buyer-side checklist, in order.

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AI Trading3 Nov 20268 min read

AI Agents Are Trading Real Money Now — Here Is the Verified Record, Not the Hype

Forget the screenshots. On-chain and venue data from November 2026 shows what AI agents, vaults, and apps actually did with real money — and 17 of 18 advertised claims still can’t be checked.

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Prop Firms3 Nov 20267 min read

92% Fail FTMO — The Math Behind Prop Firm Failure

FTMO's own data says 92% of traders fail its challenge. The cause isn’t bad strategies — it’s one rule, one morning, and position sizes that make failure a matter of time.

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Data3 Nov 20268 min read

SEBI’s FY26 Data: 88% of Retail F&O Traders Lost ₹91,685 Crore

SEBI's August 2026 study is out: 87.7% of individual F&O traders lost money in FY26, options drove 92% of losses, and participation fell 20%. The numbers are brutal — and barely moved.

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AI Trading3 Nov 20267 min read

ChatGPT Can’t Backtest: Why “AI” Trading Bots With 10-Year Backtests Are Fiction

A bot that needs live ChatGPT calls cannot have a 2019 backtest — ChatGPT didn’t exist. That single fact exposes most “AI EAs” on the market.

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AI Trading3 Nov 20268 min read

Jane Street Made $39.6 Billion While AI Trading Contests Lost Money

Bloomberg reported Jane Street’s $39.6B trading revenue in 2025. Meanwhile, public contests pitting leading AI models against markets mostly lost money. Both get called “AI trading.” Only one description is honest.

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Execution3 Nov 20267 min read

Grid Bots and the Annualised APR Trick: How a 3% Fortnight Becomes “300% APR”

A grid bot earned ~3% in two weeks in a sideways market — then stalled when price broke range. The dashboard annualised that fortnight into a triple-digit APR. Here is the trick, step by step.

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Prop Firms3 Nov 20267 min read

The Daily Drawdown Trap: Why One Bad Morning Ends Your Prop Challenge

You can be net profitable for two weeks and still fail a prop challenge — because one bad morning breached the daily cap. The rule, the math, and how to survive it.

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Checklist3 Nov 20268 min read

From Backtest to Funded Account: The Validation Checklist Prop Traders Need Before Paying

Challenge fees are $200–$1,000+ per attempt, and ~90% of attempts fail. This checklist — run before you pay, not after — is the cheapest money in prop trading.

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AI Trading3 Nov 20267 min read

Crypto AI Vaults: 3 of 6 Beat Bitcoin, 1 Fell 30% — What That Actually Proves

The most checkable corner of AI trading is Hyperliquid vaults — public numbers, no screenshots. The verified record is mixed, and the mix itself is the lesson.

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Synthesis3 Nov 20268 min read

9 Out of 10 Lose: The Real Odds in Retail Trading, and the Only Edge That Matters

SEBI: 88% of F&O traders lost money. FTMO: 92% fail. AI apps: most users lost. Three different markets, one pattern — and one edge that actually changes the odds.

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Written to the same standard as the listing.

No article here promises a return, sells a signal, or describes the harness as more than it is. Walk-forward means period stability, not purged walk-forward. PBO needs a candidates file and is never a gate. Accuracy is always recomputed from raw predictions, never taken from a claimed column.

If an essay says a check exists, you can read exactly what it does and where its boundary is on the eight checks

A backtest should have to prove itself.

That is the whole product: a harness that recomputes the number, beats it against baselines, and returns a verdict with an exit code.

Enquire about the sale See the eight checks