---
name: code-style
description: "Enforce mirror, reuse, and symmetry principles to keep new code consistent with surrounding code. Use when writing new code in an existing codebase, adding new features, refactoring, or making any code changes."
---
# Code Style: Mirror, Reuse, Symmetry
When writing new code in an existing codebase, follow these principles:
1. **Mirror the surrounding code exactly**: Match brace style, comment style, naming conventions, blank line spacing, code density, and level of detail by reading nearby code first.
2. **Reuse existing patterns**: Find the closest analogous feature and replicate its structure (method decomposition, control flow, annotations, guard clauses). Don't introduce new patterns when an existing one fits.
3. **Reuse existing code**: Before writing a new helper, check if an existing method can be reused or generalized. If a new helper is needed, model it after its closest sibling.
4. **Maintain symmetry**: If adding `fooB()` parallel to `fooA()`, ensure naming, parameter order, and structure are symmetric. Rename `fooA()` if needed.
5. **Logical ordering**: Place new methods, switch cases, and fields in the order that mirrors the existing grouping or business lifecycle, not just appended at the end.
6. **Default to no comment**: Write code that self-explains through naming, extraction, and structure. When you reach for a comment, first try refactoring so it becomes unnecessary. Add one only for a load-bearing constraint the code cannot express (a hidden invariant, a workaround, a non-obvious performance characteristic). When in doubt, omit it.