subtractive-debugging

Regression isolation works by subtracting from a known-good baseline while preserving a stable control, comparing entity signatures at one closure layer to find the first cascaded mismatch. You first collapse the history interval, then shrink the changed-entity set to pinpoint the boundary.

Subtractive debugging isolates regressions by comparing entity signatures at a specific surface layer rather than raw file churn. Unlike standard git bisect, it collapses the history interval first, then subtracts the changed-entity set to name the first cascaded mismatch with deterministic evidence.

To set up a deterministic surface checker, define a stable control, exact property targets, and known-good plus current bad baselines. The checker validates a narrow property at a single closure layer like loader, schema, import, runtime, or artifact render.

Yes, regression isolation applies to any single closure layer including loader, schema, import display, runtime behavior, or artifact render. You narrow comparison to that specific surface to make differences actionable and reduce noise from wide diffs.

Subtractive debugging compares entity signatures, such as IDs and required-field sections, to reduce noise from wide diffs caused by broad code and import churn. This signature-based comparison ensures the introducing boundary is found with actionable evidence.

You should avoid subtractive debugging when you cannot define a narrow property to validate or lack a deterministic surface-specific checker. It requires a stable control and exact baselines, making it unsuitable for non-deterministic behaviors or broad speculation without clear targets.