Codemod

This gives Claude systematic knowledge about writing AST-based code transformations using tools like ast-grep and JSSG. The skill covers 48 rules across pattern matching, node traversal, semantic analysis, and edit operations, all prioritized by impact. You'd want this when building codemods for automated refactoring, migrating codebases between API versions, or debugging why your transformation is matching the wrong nodes. The focus on idempotency, batched edits, and test fixtures shows real production experience. One thing that stands out is the emphasis on exploring ASTs before writing patterns and using constraints to avoid overly generic matches, which are exactly the mistakes that lead to broken migrations at scale.

skills.sh installs: 334
GitHub stars: 222
last updated: Aug 21, 2026

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Install

$ npx -y skills add pproenca/dot-skills --skill codemod --agent claude-code

Installs into .claude/skills of the current project.

Files

Codemod Best Practices

Comprehensive best practices guide for Codemod (JSSG, ast-grep, workflows), designed for AI agents and LLMs. Contains 48 rules across 11 categories, prioritized by impact to guide automated refactoring and code generation.

When to Apply

Reference these guidelines when:

Writing new codemods with JSSG or ast-grep
Designing workflow configurations for migrations
Debugging pattern matching or AST traversal issues
Reviewing codemod code for performance and safety
Setting up test fixtures for transform validation

Rule Categories by Priority

Priority	Category	Impact	Prefix
1	AST Understanding	CRITICAL	`ast-`
2	Pattern Efficiency	CRITICAL	`pattern-`
3	Parsing Strategy	CRITICAL	`parse-`
4	Node Traversal	HIGH	`traverse-`
5	Semantic Analysis	HIGH	`semantic-`
6	Edit Operations	MEDIUM-HIGH	`edit-`
7	Workflow Design	MEDIUM-HIGH	`workflow-`
8	Testing Strategy	MEDIUM	`test-`
9	State Management	MEDIUM	`state-`
10	Security and Capabilities	LOW-MEDIUM	`security-`
11	Package Structure	LOW	`pkg-`