ml4t-lookahead-bias skillA
ml4t-lookahead-bias is agent-read markdown (skill) from ml4t/skills: Detect future information leaking into features, labels, or evaluation. Use when any pipeline step might expose data not yet available at prediction time..
Indexed from public GitHub and served as immutable, content-addressed versions. Install it pinned to an exact SHA-256 with the mdr CLI, and every file is verified against the hash recorded here before it reaches your agent. The deterministic audit below grades the latest version, and the same file always earns the same grade.
What the file says
# Lookahead Bias The most common ML4T failure. A model uses future information during training - normalization with full-sample statistics, labels from future thresholds, standard k-fold CV on time series - producing a great backtest that fails immediately in production. ## The Problem Lookahead bias means using information that would not have been available at prediction time. It inflates backtest Sharpe and is the #1 reason strategies fail live. Common sources: full-sample normalization, future-based thresholds, train+test preprocessing, and shuffled CV on time series. ## The Pattern ### WRONG ```python from sklearn.preprocessing import StandardScaler # Normalize features using full dataset statistics (future leak) scaler = StandardScaler() X_scaled = scaler.fit_transform(X) # mean/std computed on ALL data including test # Label threshold from full history (future leak) threshold = returns.quantile(0.75) # Uses future returns to set threshold y = (forward_returns > threshold).astype(int) # Shuffled k-fold on time series (future leak) from sklearn.model_selection import KFold cv = KFold(n_splits=5, shuffle=True) # Training on 2024 data, testing on 2020 ``` …
Read the whole file at its exact version.
How to install
mdr add ml4t/skills/ml4t-lookahead-bias@git:20260901.c415df0mdr add ml4t/skills/ml4t-lookahead-bias@sha256:26d18ce123aabee4Pin to a label to follow the author's releases, or to a sha256 to freeze the exact bytes forever. Either way the resolved hash is written to mdr.lock, and mdr install reproduces it on any machine.
[](https://markdownregistry.com/a/art_tjkbw73l7bhfigpz)
1 badge views in 30 days
Versions
| version | committed | commit | size | audit | |
|---|---|---|---|---|---|
| git:20260901.c415df0 latest | 2026-09-01 | c415df0 | 4,271 B | A | view · diff |
| git:20260528.303089e | 2026-05-28 | 303089e | 4,320 B | A | view |
Audit of the latest version
- pass: Frontmatter block present
- pass: Frontmatter declares a name
- pass: Frontmatter declares a description
- pass: Size between 200 bytes and 200 KB (4271 bytes)
- pass: No zero-width or bidi control characters
- pass: No instruction hidden inside an HTML comment
- pass: No link to an exfiltration or paste host
- pass: No credential-shaped string
- pass: No instruction to send local credentials anywhere
- pass: No text hidden with inline styles
- pass: No prompt-injection phrasing
- pass: No curl or wget piped into a shell
- pass: No recursive delete of root, home or parent
- pass: No instruction to read or print local credentials
- pass: No base64 blob over 200 characters
- pass: No link to a raw IP address
- pass: No script tag
Source
ml4t/skills · 19 stars · license Apache-2.0 · pushed 2026-09-24 · branch main
API
GET https://markdownregistry.com/api/v1/artifacts/art_tjkbw73l7bhfigpz GET https://markdownregistry.com/api/v1/resolve?ref=ml4t/skills/ml4t-lookahead-bias GET https://markdownregistry.com/api/v1/blob/26d18ce123aabee4822dc35325a517690c1b03ac6f04de761ff3d3c7aeaf6695
Your agent does the legwork. You hear about the deals worth your word. Hand yours the standing instructions at modelranch.com and it joins the network that reads files like this one.