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Large Language ModelsAI Coding AssistantsQiita 機械学習Published: Nov 12, 2026, 19:01 JST

Cursor, Claude Code, Codex: split roles for horse-racing AI, engineer says

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Cursor, Claude Code, Codex: split roles for horse-racing AI, engineer says

3 Key Points

  1. What happened

    Writing from roughly eight years of engineering experience, about three of them in AI development, the author concluded that horse-racing prediction models are best built by splitting work across Cursor, Claude Code, and OpenAI Codex rather than picking one winner.

  2. Why it matters

    The author recommends using Cursor as the main development environment, Claude Code as a design and implementation partner, and Codex as a verification and review partner, so that implementation and validation are not left to the same AI.

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Context & Analysis

Cursor, Claude Code, and OpenAI Codex are not the same kind of product. Cursor is described as an AI-integrated code editor suited to editing, implementation, and debugging, while Claude Code and Codex are positioned as AI coding agents that can work across multiple files and tasks. That distinction is why the author treats the three as complements rather than substitutes: Cursor is a daily working environment, Claude Code is suited to understanding an existing codebase and planning changes across files, and Codex is valued for independent review and parallel work.

The horse-racing AI example is used to show where that division matters. A prediction model has to combine many inputs — horse ability, jockey, trainer, track, distance, track condition, post position, past results, and odds — and it also needs backtesting and ROI checks. The author warns against data leakage, such as mixing in finishing order or payouts that are only known after a race, and recommends starting with simpler models like Logistic Regression or LightGBM before trying more complex ones. In that setting, having one AI write the model and a different AI check it is presented as a way to make the development process verifiable rather than merely fast.

The author is careful to separate personal experience from tested results. A roughly 22,000-line, 196-file, 54-commit system was delivered in 19 days, and a roughly 7.5-hour prototype was built with Claude Code, but these are system-development achievements, not measured hit rates or ROI for a horse-racing AI. The proposed 10-task, three-run-per-tool comparison is likewise framed as a future experiment. The closing point is that design and statistical evaluation skills remain the deciding factor, with AI coding tools acting as a means to speed up that work.

FAQ
What is the author's recommended setup for building a horse-racing AI?
Use Cursor as the main development environment, Claude Code as the design and implementation partner, and OpenAI Codex as the verification and review partner. This combines the three tools rather than choosing only one.
Does using these AI coding tools automatically improve prediction accuracy?
No. The author states that introducing the latest AI coding tools does not automatically improve prediction accuracy. What matters is which data you collect, which features you design, which model you adopt, and how you validate it.
What metrics does the author say matter more than hit rate?
The author emphasizes return on investment (ROI) over hit rate. Log Loss and Brier Score are also important for probability predictions, and out-of-sample backtesting over a period is recommended rather than judging from one or a few results.
Has the author measured the 30-run comparison experiment?
No. The author presents it as a design for a future comparison experiment, not as measured results.
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