Rare Events and Edge Cases: Where Synthetic Data Wins
Training AI on rare events is hard. Real data is often too sparse, too costly to collect, or too risky to expose. Synthetic data solves the problem by generating realistic scenarios that are impossible to capture in production.
The math is brutal for rare classes
In a typical dataset, 99.9% of samples are common cases. The remaining 0.1% might be fraud, critical errors, or rare medical conditions. With only a few hundred examples, a model cannot learn robust boundaries. Real-world experiments show that models trained on 10,000 synthetic rare events can outperform models trained on just 100 real examples when the real examples are noisy or imbalanced.
Edge cases need diversity, not just volume
Edge cases are not just rare, they are varied. A single real fraud transaction may have different device fingerprints, locations, and time-of-day patterns. Synthetic data lets you generate thousands of distinct edge cases that preserve the statistical properties of real data while introducing controlled variations. For example, you can create 5,000 variations of a rare checkout error, each with unique combinations of user behavior, network conditions, and UI state.
Two proven techniques for synthetic edge cases
- ●Latent space interpolation: Generate new samples by interpolating between two real edge cases in a learned feature space. This creates smooth transitions that expose boundary behavior.
- ●Reverse-engineer from logs: Extract the last known states and actions before an edge case occurred, then run simulation to generate full trajectories for training and evaluation.
The takeaway: synthetic data does not replace real data. It complements it by providing the volume and diversity needed to learn rare events and edge cases that are otherwise invisible to the model.
How Coasty fits
Coasty runs computer use agents on real desktops and browsers. This allows us to capture realistic interaction data and produce synthetic datasets and trajectories for training and evaluating agents and models. The service is custom and contact-led, so you can specify the rare events and edge cases that matter most for your use case.
If you need more rare events or edge cases for your AI, book a data call with the Coasty data team at https://cal.com/coasty/coasty-data-call. We’ll help you design a synthetic data strategy that matches your real-world needs.