RealDiff Diffs Runtime Behavior Instead of Source, Across Six Languages
RealDiff checks out both branches into isolated worktrees, builds each with instrumentation, runs the same tests on both sides and compares actual method arguments and return values, then filters noise by running the base repeatedly and collapses results to the 'frontier' where a change originates. Its documented example follows execution from an edited ordering helper into unedited pricing code and reports the changed values there, which is the class of regression a source diff will not show. It covers .NET 8 via Mono.Cecil, Java via a javaagent with ASM, Node/TypeScript via Babel, Go and Rust via AST rewriting, and Python 3.12+ via PEP 669 sys.monitoring; MIT licensed, 33 stars, and it only asks an LLM to explain findings it already proved deterministically.
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