# Backtest breaker

- **Event:** [Meta Global AI Developer Hackathon](https://cerebralvalley.ai/e/meta-ai-developer-hackathon)
- **When:** Oct 26, 12:00 PM – Nov 4, 9:00 PM (EST)
- **Where:** Online
- **Team:** [Ela Kumuk](https://cerebralvalley.ai/u/elakumuk)
- **GitHub:** https://github.com/elakumuk/backtest-breaker
- **Demo video:** https://youtu.be/qfv_FggLAbY
- **Gallery:** https://cerebralvalley.ai/e/meta-ai-developer-hackathon/hackathon/gallery
- **Page:** https://cerebralvalley.ai/e/meta-ai-developer-hackathon/hackathon/gallery/1401

Backtest Breaker is an AI that tries to break your trading backtest before the market does. One Muse Spark agent searches for a strategy on in-sample data. A second Muse Spark agent attacks the winner with tool calls (walk-forward, parameter sensitivity, cost stress, Deflated Sharpe, PBO), writes down a prediction, and then opens a hash-sealed holdout exactly once. Deterministic code computes every number, and a code rubric gives the final verdict.

In our live run, Muse Spark mostly refused to overfit. The one exception was trial 13, where it set trading costs to zero, and that trial became the in-sample winner at a Sharpe of 0.68. The auditor predicted a holdout Sharpe of 0.32; the sealed holdout came in at 0.30. The model still called the strategy "SURVIVES"; the rubric overruled it: FRAGILE. Notebook mode reads a user's .ipynb, finds look-ahead leaks, and marks a finding PROVEN only if a generated test fails on the bug, passes with the fix, and passes on a clean control. On a held-out set we wrote outside the repo, every PROVEN finding was real (precision 1.00), with zero false alarms on clean code.

## More from Meta Global AI Developer Hackathon

- [Ajd](https://cerebralvalley.ai/e/meta-ai-developer-hackathon/hackathon/gallery/1398)
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- [RealityReplay Labs](https://cerebralvalley.ai/e/meta-ai-developer-hackathon/hackathon/gallery/1400)
- [CX10](https://cerebralvalley.ai/e/meta-ai-developer-hackathon/hackathon/gallery/1402)
- [GeoWade AI](https://cerebralvalley.ai/e/meta-ai-developer-hackathon/hackathon/gallery/1403)
- [SnapFix](https://cerebralvalley.ai/e/meta-ai-developer-hackathon/hackathon/gallery/1404)

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