Refine Code with Minimal Changes

Moyu is an anti-over-engineering guardrail for coding assistants. It aims to keep changes within the user's stated scope, favor the simplest viable implementation, and avoid unrelated abstractions, refactors, formatting, dependencies, and adjacent features. Its central review question is whether each added line and touched file is necessary for the requested result.

Follow three rules: change only what was asked, look for a simpler solution before coding, and clarify uncertainty about expanded scope. It encourages reusing existing implementations, using built-in language features, keeping code near its use, and avoiding new files or architectural layers without a concrete need.

Use Moyu when a small request starts spreading into unrelated changes or when a coding workflow tends to add speculative extensibility. It can help review a patch for unnecessary renaming, formatting, documentation, configuration, or dependency additions. Make one change at a time with verification before proceeding.

The guardrail explicitly does not restrict work the user actually requested. Comprehensive error handling, a module refactor, tests, or documentation remain in scope when requested. Its restrictive examples about tests and documentation should also be reconciled with the real project's validation requirements rather than interpreted as evidence that an unverified change is safe.

Inputs are the original request, the code and files it concerns, the current diff, and existing reusable implementations. Outputs are a smaller scoped patch, a list of proposed scope expansions requiring clarification, or a revised minimal approach. The workflow contrasts direct implementation with premature interfaces and factories, boundary validation with speculative internal checks, and concise local constants with unnecessary configuration systems.

The delivery checklist asks whether edits were requested, whether fewer lines could achieve the result, whether every addition is necessary, whether existing code was searched first, and whether unrequested collateral work has entered the diff. It also uses a short-review target to prompt restraint, not to establish an objective quality guarantee.

Four intervention levels describe escalating responses. L1 removes a small number of unnecessary changes and continues the actual task. L2 stops an overcomplicated approach, rereads the request, and reimplements more simply when new files, dependencies, abstraction layers, or broad rewrites appear. L3 inventories edits, separates requested work from collateral changes, and removes nonessential work after wider scope violations, configuration changes, deletion, or cascading fixes. L4 stops operations when a small request has become a large diff, a repeated failure loop, or explicit user dissatisfaction, then restates the request and seeks agreement on a minimal solution.

The numerical triggers are heuristic signals. A large necessary change is not automatically wrong, and a short patch still needs to satisfy the actual task. Complete authorized work without adding work the user did not ask for.

Moyu complements PUA, a separate workflow aimed at excessive passivity. It does not document a software API, runtime installation, or external service connection for that pairing.

Moyu supports people directing coding assistants and developers reviewing narrow changes. It provides a scope-control checklist and course-correction framework rather than a substitute for repository-specific validation or review.