We've been building an open source tool called sem (https://github.com/ataraxy-labs/sem) that takes this one level further: entity-level diffs instead of AST-level.

Instead of showing you which syntax nodes changed, it shows you which functions, classes, and methods changed, classifies the change (text-only, syntax, functional), and walks a dependency graph to tell you the blast radius.

The delta + difftastic integration problem in that issue is interesting because sem already has the pieces both sides need, before/after content with full context for every changed entity, plus structured JSON output. The blocker in #535 is that difftastic's JSON doesn't include surrounding context. sem's output includes complete entity bodies by default.

Would love to collaborate on a common interchange format if anyone from the delta or difftastic projects is interested. Entity-level granularity sits naturally above AST-level diffs and below file-level diffs, and having a standard way to represent "what changed and what depends on it" would be useful for the whole ecosystem.