ml4t-lookahead-bias SKILL.md skillA
ml4t-lookahead-bias from ml4t/skills is an agent skill: a SKILL.md folder an AI agent loads when a task calls for it.
mdr add ml4t/skills/ml4t-lookahead-bias@git:20260901.c415df0Pins git:20260901.c415df0 in mdr.lock. Pin the fingerprint instead.
- Audit grade
- A, 17 of 17 checks passed
- Kind
- SKILL.md skill
- Repository
- ml4t/skills
- Path
concepts/lookahead-bias/SKILL.md- Versions recorded
- 2
- Latest version
- git:20260901.c415df0, committed Sep 1, 2026
- First version recorded
- May 28, 2026
- Size
- 4,271 bytes
- Repository stars
- 41
- License
- Apache-2.0
Detect future information leaking into features, labels, or evaluation. Use when any pipeline step might expose data not yet available at prediction time.
Collected from public GitHub. Every version is saved exactly as it was and never changes. Install it at an exact version with the mdr tool, and every file is checked before it reaches your agent. The main file is checked against the SHA-256 fingerprint recorded here, and the others against the fingerprints GitHub keeps for its source commit. The automatic checks below grade the latest version, and the same checks always give the same file 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@sha256:26d18ce123aabee4The line at the top of this page pins the label git:20260901.c415df0, which is what most people want. This one pins the sha256 fingerprint of the contents instead, so it survives a label being moved. Either way the exact version is written to mdr.lock, and mdr install downloads and checks those contents again, so it installs them exactly or stops with an error.
[](https://markdownregistry.com/a/art_tjkbw73l7bhfigpz)
2 badge image fetches in 30 days. What the badge shows.
Versions
The registry has recorded 2 versions of this file, between May 28, 2026 and Sep 1, 2026, about one every 96 days.
| 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 · 41 stars · license Apache-2.0 · pushed 2026-11-08 · 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 AI assistant 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.
Guides: the SKILL.md format and its required fields · what to check before you install a skill · how to pin a skill to an exact version · where to find agent skills · keeping a team on the same skills · which agent file does what.