# Main Directories in the Automattic Harper Repository: Complete Monorepo Guide > Explore the main directories in the Automattic Harper monorepo. Understand the structure of this Rust-based grammar-checking ecosystem, including its core engine, WebAssembly bindings, and IDE integrations. - Repository: [Automattic/harper](https://github.com/Automattic/harper) - Tags: how-to-guide - Published: 2026-08-01 --- **The Automattic Harper repository organizes its grammar-checking ecosystem as a Rust-based monorepo with over a dozen top-level directories separating the core engine, WebAssembly bindings, language server, IDE integrations, and desktop application.** The Harper repository groups independent components into distinct crates and packages, making it possible to use the grammar engine in browsers, editors, and command-line tools. Understanding the main directories in the Automattic Harper repository helps contributors navigate the separation between the rule engine in `harper-core`, the WebAssembly bridge in `harper-wasm`, and the various editor plugins housed under `packages/`. ## Core Grammar Engine ### harper-core The foundation of the entire project, `harper-core` contains the rule engine, tokenizers, and default configuration files that power all Harper products. The public API is exposed in [`harper-core/src/lib.rs`](https://github.com/Automattic/harper/blob/main/harper-core/src/lib.rs), which defines the primary interfaces for linting text and applying grammar rules. ### harper-wasm This directory compiles the core engine to WebAssembly, enabling browser-based usage through JavaScript environments. The WASM bindings are implemented in [`harper-wasm/src/lib.rs`](https://github.com/Automattic/harper/blob/main/harper-wasm/src/lib.rs), exposing the Rust engine to web applications like the [`harper.js`](https://github.com/Automattic/harper/blob/main/harper.js) package. ### harper-ls Implements the Language Server Protocol (LSP) used by VS Code, Neovim, Helix, and Zed. The server entry point is located at [`harper-ls/src/main.rs`](https://github.com/Automattic/harper/blob/main/harper-ls/src/main.rs), which initializes the LSP runtime and connects the core engine to editor clients. ## Parsing and Linguistic Utilities ### harper-comments Contains parsers that extract comments from source code in many programming languages, allowing the linter to check documentation and inline comments. The central extraction logic resides in [`harper-comments/src/lib.rs`](https://github.com/Automattic/harper/blob/main/harper-comments/src/lib.rs). ### harper-tree-sitter Houses Tree-sitter grammars that enable fast, incremental parsing of source files. These grammars provide the syntactic structure needed by `harper-comments` to locate comment boundaries accurately. ### harper-pos-utils Utilities for part-of-speech tagging, including a Brill-style tagger and supporting dictionaries. The POS-tagging API is defined in [`harper-pos-utils/src/lib.rs`](https://github.com/Automattic/harper/blob/main/harper-pos-utils/src/lib.rs). ### harper-brill Contains trained models and runtime infrastructure for the Brill tagger used by the POS utilities. This directory separates the machine learning artifacts from the tagging logic itself. ## Specialized Linting Tools ### harper-ink A domain-specific linter for Ink story files used in interactive fiction and narrative games. ### harper-jjdescription Parses and validates "JJ" commit descriptions according to the project's internal commit style guidelines. ### harper-git-commit Linter for conventional Git commit messages, ensuring standardized formatting in version control history. ### harper-thesaurus A lightweight thesaurus implementation providing synonym suggestions and lexical enrichment for suggestions. ### harper-stats Data-collection utilities that record lint-run statistics for internal analytics and performance monitoring. ## User Interfaces and Integrations ### packages A collection of first-party integrations and UI packages organized into subdirectories: - `chrome-plugin` – Browser extension for Chrome and Firefox - `vscode-plugin` – Visual Studio Code extension wrapper - `obsidian-plugin` – Integration for the Obsidian knowledge base - `wordpress-plugin` – WordPress editor integration - [`harper.js`](https://github.com/Automattic/harper/blob/main/harper.js) – JavaScript wrapper consuming the WASM engine (entry point at [`packages/harper.js/src/index.ts`](https://github.com/Automattic/harper/blob/main/packages/harper.js/src/index.ts)) - `harper-editor` – Shared Svelte components used by the website and desktop application - `web` – Public documentation site and demo application (source at `packages/web/src/routes/docs/about/+page.md`) ### harper-desktop The Tauri-based desktop application providing an offline editor, system tray UI, and overlay highlighter. The binary entry point is located at [`harper-desktop/src-tauri/src/main.rs`](https://github.com/Automattic/harper/blob/main/harper-desktop/src-tauri/src/main.rs). ## Development and Testing Infrastructure ### fuzz Contains fuzzing harnesses used to stress-test the core engine and uncover edge cases in the grammar rules. ### docker-compose.yml Configuration files for Docker-based development, enabling contributors to run the full stack locally without installing Rust toolchains or Node.js dependencies. ## Building Components from Source Navigate to specific directories to build or test individual components: ```bash # Build the core Rust engine cargo build -p harper-core # Compile the WebAssembly bundle for browser usage cd harper-wasm && wasm-pack build --release # Run the LSP server locally for editor integration cd harper-ls && cargo run --release # Test comment extraction on sample files cargo test -p harper-comments --lib # Launch the Tauri desktop application cd harper-desktop && just dev-desktop ``` The `justfile` in the repository root provides convenient shortcuts for common tasks like `just test` and `just format`, orchestrating builds across the monorepo's multiple crates. ## Summary - **`harper-core`** contains the essential grammar engine and rule system at [`harper-core/src/lib.rs`](https://github.com/Automattic/harper/blob/main/harper-core/src/lib.rs) - **`harper-wasm`** and **`harper-ls`** provide WebAssembly and LSP bindings for web and editor integration - **`harper-comments`** and **`harper-tree-sitter`** handle source code parsing and comment extraction - **`packages/`** houses all user-facing integrations including VS Code, Obsidian, and the [`harper.js`](https://github.com/Automattic/harper/blob/main/harper.js) wrapper - **`harper-desktop`** delivers a standalone Tauri application for offline usage - Supporting directories like **`harper-pos-utils`**, **`harper-brill`**, and **`harper-stats`** provide linguistic analysis and analytics capabilities ## Frequently Asked Questions ### What is the purpose of the harper-core directory? The `harper-core` directory contains the fundamental grammar-checking engine, including the rule engine, tokenizers, and default configuration files. All other packages in the monorepo depend on this crate, which exposes its public API through [`harper-core/src/lib.rs`](https://github.com/Automattic/harper/blob/main/harper-core/src/lib.rs). ### How does harper-wasm relate to the JavaScript packages? The `harper-wasm` directory compiles the Rust core engine into WebAssembly, creating the binary module consumed by [`packages/harper.js`](https://github.com/Automattic/harper/blob/main/packages/harper.js). This allows the JavaScript wrapper to instantiate the grammar checker in browsers and Node.js environments without requiring a native Rust toolchain on the user's machine. ### Which directory contains the VS Code extension? The VS Code extension source code resides in `packages/vscode-plugin/`, while the underlying Language Server Protocol implementation it communicates with is located in `harper-ls/`. The extension wraps the LSP binary and provides UI components specific to the VS Code ecosystem. ### What is the difference between harper-comments and harper-tree-sitter? `harper-tree-sitter` contains Tree-sitter grammars for parsing source code syntax, while `harper-comments` uses those grammars to extract comment text from specific locations in the parse tree. The tree-sitter crate provides the parsing infrastructure, and the comments crate implements the logic for identifying and extracting comment content across multiple programming languages.