Codemod — AI-Powered Code Migration CLI

What it is

Codemod is an AI-powered command-line tool for scaffolding, sharing, and running large-scale code migrations. It supports ast-grep for AST-based pattern matching, multi-step YAML workflows for complex migrations, and a community registry of pre-built codemods for common framework upgrades (Next.js, React, etc.).

Codemod targets developers and teams facing framework upgrades, API deprecations, or codebase-wide refactoring. Instead of manual find-and-replace or writing custom scripts, you run a codemod that understands your code's syntax tree.

How it saves time or tokens

Manual code migration is error-prone and tedious at scale. Codemod automates transformations using AST awareness, meaning it understands code structure rather than treating it as text. Pre-built codemods in the registry handle common migration paths (e.g., Next.js 12 to 13 app router). Creating your own codemods lets you share migration logic across teams and projects.

How to use

1. Run a community codemod: npx codemod @codemod/next/13/app-router to apply a pre-built migration.
2. Create your own codemod: npx codemod init my-migration to scaffold a new codemod project.
3. Publish to the registry: npx codemod publish my-migration to share with others.

Example

# Apply a community codemod
npx codemod @codemod/next/13/app-router

# Create a custom codemod
npx codemod init my-migration
cd my-migration

# Define transformation in codemod.yaml
# Uses ast-grep patterns for AST matching

# codemod.yaml example
name: replace-deprecated-api
engine: ast-grep
pattern: 'oldFunction($ARGS)'
fix: 'newFunction($ARGS)'
language: typescript

Related on TokRepo

• Coding AI Tools — AI-powered development and refactoring tools
• Automation Tools — Code automation and migration tools

Common pitfalls

• Codemods modify source files in place. Always commit your code before running a codemod so you can revert if the transformation produces unexpected results.
• AST-based transformations are language-specific. A TypeScript codemod will not work on Python code. Verify the codemod targets your language.
• Community codemods may not cover all edge cases in your codebase. Review the diff after running and handle edge cases manually.