# Codemod

> Codemod provides tools and infrastructure to automate repetitive or large-scale code maintenance projects end-to-end, effectively making them invisible to software teams. The platform pairs compiler-aware code graphs with AI to complement coding agents across the SDLC — from planning and large-scale code transformations to orchestration and leadership visibility.

Codemod is used by projects like React, Node.js, ESLint, Nuxt, pnpm, MSW, Webpack, and React Router.

## Use Cases

- Framework or library upgrades (React, Node.js, etc.)
- Security compliance — scan for vulnerable code patterns and automate patching across codebases
- Design system migrations (Radix, Tailwind, etc.)
- Internationalization — converting static strings to translation keys
- Codebase sanitization after M&A or spin-off
- Dependency management at scale

## Core Components

**Codemod CLI** — Open-source CLI for scaffolding, testing, publishing, and running codemods locally. Run published packages directly with `npx codemod <package-name>`, or develop and test transforms with `npx codemod jssg run` and `npx codemod jssg test`.

**Codemod Studio** — Web-based tool where you describe a change in plain language and Codemod AI generates a working codemod (YAML ast-grep rule or JSSG script). Includes test case management, AST visualization, and shareable links.

**Codemod Registry** — Centralized repository for discovering, consuming, and distributing codemod packages. Supports public and private packages, scoped organization namespaces, semantic versioning, and direct execution via `npx codemod`. The registry includes **Pro Codemods** — expert-built codemods for complex large-scale migrations, available to Starter and Enterprise tier customers.

**Campaigns** — Orchestrate large-scale code migrations across teams and repositories. Campaigns execute workflows, create tasks, open pull requests, and provide centralized progress tracking.

**Workflows** — Execution engine that orchestrates automated code transformations at scale. Defined in `workflow.yaml`, workflows consist of nodes (execution units with dependencies) and steps (atomic actions: JSSG transforms, ast-grep rules, shell commands, AI agents, or registry codemods). Supports matrix strategies for parallelization, state persistence for resumable migrations, and cross-repository coordination.

**JSSG (JavaScript ast-grep)** — Secure JavaScript runtime for building codemods. Transforms are authored in JavaScript or TypeScript but operate on 20 supported languages: Angular, C, C#, C++, CSS, Elixir, Go, HTML, Java, JavaScript, JSON, Kotlin, PHP, Python, Ruby, Rust, Scala, TSX, TypeScript, and YAML. Built on QuickJS with ast-grep for AST pattern matching. Follows a deny-by-default security model where file system access, network requests, and process spawning require explicit capabilities.

**Insights** — Analytics dashboards for tracking migrations, old/new APIs, security anti-patterns, and code trends across large codebases. Generate customized widgets to monitor code posture and make data-driven decisions.

**Codemod MCP (Model Context Protocol)** — MCP server that gives AI assistants (Claude, Cursor, etc.) tools for AST analysis, codemod creation, and testing. Tools are exposed to clients namespaced with the server ID (for example, `codemod_dump_ast`, `codemod_get_node_types`, `codemod_run_jssg_tests`, `codemod_get_jssg_instructions`, `codemod_get_jssg_utils_instructions`, and `codemod_get_codemod_cli_instructions`).

## Technology

Codemod's CLI and workflow engine are built in Rust. The core workflow engine handles scheduling, parallelization, state management, and coordination. JSSG runs on QuickJS with LLRT for Node.js module compatibility and oxc for module resolution. Semantic analysis supports JavaScript/TypeScript (via oxc) and Python (via Ruff). AST pattern matching is powered by ast-grep. The platform integrates with GitHub, GitLab, Jira, and supports SAML SSO.

## Who It's For

- **Enterprise engineering teams**: Platform engineers, security engineers, i18n engineers, and engineering leaders automating code migrations at scale.
- **Open-source maintainers**: Framework, library, and SDK builders who want to publish official codemods with each release and provide upgrade paths for users.

## Links

- [Homepage](https://codemod.com)
- [Platform](https://go.codemod.com/app)
- [Registry](https://go.codemod.com/registry)
- [Studio](https://go.codemod.com/studio)
- [GitHub](https://github.com/codemod/codemod)
- [Community (Slack)](https://go.codemod.com/community)

## Documentation

### Getting Started
- [Introduction](https://docs.codemod.com/introduction): Platform overview and core concepts
- [Changelog](https://docs.codemod.com/changelog): Product updates and release notes

### Enterprise
- [Enterprise Quickstart](https://docs.codemod.com/platform/quickstart): Run your first codemod and create a PR
- [Campaigns](https://docs.codemod.com/platform/campaigns): Multi-repo migration orchestration with automated PRs
- [Insights](https://docs.codemod.com/platform/insights): Codebase analytics and migration tracking dashboards
- [Registry](https://docs.codemod.com/platform/registry): Public and private package management
- [Codemod Studio](https://docs.codemod.com/platform/codemod-studio): AI-powered codemod creation
- [GitHub Integration](https://docs.codemod.com/platform/integrations/github): Connect GitHub repositories
- [GitLab Integration](https://docs.codemod.com/platform/integrations/gitlab): Connect GitLab repositories
- [Jira Integration](https://docs.codemod.com/platform/integrations/jira): Bidirectional task sync
- [SAML SSO](https://docs.codemod.com/platform/saml): Single sign-on setup for organizations

### Community & OSS
- [Community Quickstart](https://docs.codemod.com/oss-quickstart): Scaffold, test, and publish your first codemod
- [CLI Reference](https://docs.codemod.com/cli): Full command-line tool documentation
- [Package Structure](https://docs.codemod.com/package-structure): Codemod package anatomy (codemod.yaml, workflow.yaml, scripts, rules, tests)
- [Publishing](https://docs.codemod.com/publishing): Authentication methods (interactive login, API keys, trusted publishers) and CI/CD setup
- [Model Context Protocol](https://docs.codemod.com/model-context-protocol): MCP server setup for AI assistants
- [OSS Maintainers](https://docs.codemod.com/oss): Guide for framework and library builders

### Workflows
- [Workflows Introduction](https://docs.codemod.com/workflows/introduction): Execution engine concepts (nodes, steps, scheduling, state)
- [Workflows Reference](https://docs.codemod.com/workflows/reference): Complete workflow.yaml specification

### JSSG (JavaScript ast-grep)
- [JSSG Quickstart](https://docs.codemod.com/jssg/quickstart): Build your first JSSG codemod
- [JSSG Testing](https://docs.codemod.com/jssg/testing): Validate codemods with fixtures
- [JSSG API Reference](https://docs.codemod.com/jssg/reference): SgRoot, SgNode, rules, parse helpers, and file operations
- [JSSG Metrics](https://docs.codemod.com/jssg/metrics): Collect transformation metrics
- [Semantic Analysis](https://docs.codemod.com/jssg/semantic-analysis): Cross-file type-aware transformations (JS/TS via oxc, Python via Ruff)
- [JSSG Advanced](https://docs.codemod.com/jssg/advanced): Multi-file transforms, dynamic parsing, and complex patterns
- [Import Utilities](https://docs.codemod.com/jssg/utils): Reusable helpers for import manipulation
- [JSSG Security](https://docs.codemod.com/jssg/security): Deny-by-default security model and capability configuration