The Software Behavior Diff Engine

 Build a software analysis tool that compares two versions of an application based on their observable behavior, not just textual code differences.

Allow developers to provide old and new source-code snapshots, API examples, test results, logs, or recorded interaction traces. Identify changed inputs, outputs, validation rules, error responses, side effects, and state transitions wherever the available evidence permits.

Generate a behavior comparison report that separates intentional changes, possible regressions, uncertain differences, and changes that need additional tests. Highlight cases where code has changed substantially but observable behavior appears unchanged, as well as small edits that may have broad consequences.

Create regression test suggestions with reproducible inputs and expected outcomes derived from existing specifications or verified baseline behavior. Never invent a baseline result when none is available.

Include filters for public APIs, database operations, UI behavior, business rules, and error handling. Preserve both original versions and produce a reviewable report suitable for a pull request.