Translates cryptic runtime error messages and stack traces into understandable explanations, pointing to the concrete line at fault and the most likely fix. Use when a user pastes an error they don't understand, when a stack trace is deep and the user doesn't know where to start, or when an error message misleads about the real cause.

Traces regressions to the specific commit, change, or code path that introduced the behavioral breakage. Use when a previously passing test or feature now fails, when the user asks what change caused a regression, or when bisecting a regression across commits.

Interprets and explains counterexamples produced by model checkers or property-based testing tools to make them actionable. Use when TLC, NuSMV, CBMC, or a property-based test emits a counterexample the user doesn't understand, when a trace is too long to read, or when mapping a model-level trace back to source code.

Creates minimal, reproducible test cases from bug reports to confirm the defect before and after a fix. Use when a bug is reported without a failing test, when the user needs a regression test for a fix, or when the user asks to reproduce a bug as a test.

Pinpoints the exact file, function, or line in a codebase responsible for a reported bug using static and dynamic analysis signals. Use when a bug is reported but the fault location is unknown, when narrowing down a failure to a specific code region, when triaging an issue tracker ticket, or when the user asks to locate where a bug originates.

Analyzes a codebase to quantify and locate technical debt — where it lives, what it costs, and what order to pay it down in. Use when planning a refactoring sprint, when justifying engineering time to stakeholders, when the user asks where the codebase hurts most, or when onboarding to a legacy system.

Identifies code smells — structural patterns that correlate with maintainability problems — and explains why each matters in context. Use when reviewing a PR for structural quality, when the user asks what's wrong with a piece of code that isn't buggy, or when prioritizing refactoring targets.

Optimizes code for performance by identifying the actual bottleneck, choosing the right optimization lever, and measuring the result. Use when a specific operation is too slow, when a profiler has pointed at a hot path, or when the user asks to make something faster.

Reviews and designs API contracts — function signatures, REST endpoints, library interfaces — for usability, evolvability, and the principle of least surprise. Use when designing a new public interface, when reviewing an API PR, when the user asks whether a signature is well-designed, or when planning a breaking change.

Translates pseudocode into idiomatic Python, choosing the right standard-library structures and leveraging Python idioms that pseudocode doesn't express. Use when implementing an algorithm from a paper or spec, when the user hands you pseudocode and wants Python, or when realizing a verified-pseudocode artifact.

Translates pseudocode into idiomatic Java, inferring types, choosing collection classes, and handling exceptions per Java conventions. Use when implementing an algorithm from a paper or spec, when the user hands you pseudocode and wants Java, or when realizing a verified-pseudocode artifact.

Compares the runtime behavior of two or more versions of the same code by running them on identical inputs and diffing outputs, side effects, and errors. Use when validating a refactor, port, or optimization; when the user asks if two implementations behave the same; or when investigating a suspected regression across versions.

Summarizes undocumented legacy code by inferring intent from structure, naming, data flow, and calling context — explicitly flagging what's inferred vs. what's certain. Use when onboarding to inherited code, when documentation is missing or wrong, or when deciding whether legacy code is safe to change.

Diagnoses and resolves package dependency conflicts — version mismatches, diamond dependencies, cycles — across npm, pip, Maven, Cargo, and similar ecosystems. Use when install fails with a resolution error, when two packages require incompatible versions of a third, or when upgrading one dependency breaks another.

Identifies natural component boundaries inside a monolith by clustering the dependency graph, finding the cuts with minimum coupling. Use when planning to modularize or extract microservices, when deciding what can be deployed independently, or when the user asks where the seams in this codebase are.

Produces natural-language summaries of what code does at the function, class, module, or subsystem level, with length and abstraction scaled to the scope. Explains purpose, side effects, and non-obvious behavior rather than restating syntax. Use when onboarding to unfamiliar code, when the user asks what something does, when generating docstrings or architecture notes, or when preparing a handoff document.

Finds code by meaning, structure, or text across large codebases — picks the right search strategy (grep, AST query, call graph walk, semantic search) for the question being asked. Use when the user asks where something is implemented, when navigating unfamiliar code, or when a simple grep isn't enough.

Identifies recurring structural patterns in a codebase — idioms, copy-paste clones, homegrown abstractions — and characterizes each as a reusable template. Use when learning a codebase's conventions, when hunting for copy-paste that should be a function, or when documenting how this team does things.

Swift Concurrency review and remediation for Swift 6.2+. Use when asked to review Swift Concurrency usage, improve concurrency compliance, or fix Swift concurrency compiler errors in a feature or file. Concrete actions include adding Sendable conformance, applying @MainActor annotations, resolving actor isolation warnings, fixing data race diagnostics, and migrating completion handlers to async/await.

Scaffold, build, and package SwiftPM-based macOS apps without an Xcode project. Use when you need a from-scratch macOS app layout, SwiftPM targets/resources, a custom .app bundle assembly script, or signing/notarization/appcast steps outside Xcode.