diffsitter

tree-sitter-mcp is a Claude Code plugin that provides Claude with structural understanding of code by leveraging tree-sitter AST (Abstract Syntax Tree) navigation. Instead of treating code as flat text, it allows Claude to interact with the code's actual structure.

It supports over 14 languages, including:

• Rust, Python, TypeScript, TSX, JavaScript, Go, Java, C, C++, C#, Ruby, Bash, PHP, OCaml, CSS, and HCL.

Exploring an unfamiliar codebase

1. Use list_symbols on key files to understand the high-level structure.
2. Use get_definition to read specific symbols required for understanding.
3. Use get_children_of to drill down into classes or modules.

Investigating a specific location

1. Use get_node_at_position to identify the syntax construct at a specific line/column.
2. Use get_scope to understand the nesting context.
3. Use navigate with the parent direction to walk up the AST tree.

Structural search

1. Use query with S-expressions to perform pattern matching across the AST.

When developing or manually updating the tool, use the following commands:

• Manual Rebuild: To rebuild the binary with MCP server support:

  cargo build --release --features mcp-server --bin tree-sitter-mcp

• Reloading in Claude Code: After making changes and rebuilding, you can pick up the new plugin version without restarting your Claude Code session by running the following command inside the Claude Code interface: /reload-plugins

The project uses insta for snapshot testing. If grammar updates cause snapshot tests to fail, use the insta TUI to review the differences and accept the new snapshots.

cargo insta review

For a full development experience, especially when running CI checks or reviewing tests, install the following tools:

Before submitting a Pull Request, run the following suite of commands to ensure formatting, linting, and tests pass. This matches the requirements of the CI pipeline.

cargo fmt --all -- --check
cargo clippy --all-targets --all-features -- -D warnings
cargo nextest run --all-features
cargo test --doc --all-features

If you prefer not to use the plugin hook or already have a pre-built binary, you can register the tree-sitter-mcp binary directly with Claude Code as a standalone MCP server.

1. Build the binary with the mcp-server feature enabled:

   cargo build --release --features mcp-server --bin tree-sitter-mcp

2. Register with Claude Code:

   claude mcp add tree-sitter-mcp -- ./target/release/tree-sitter-mcp

# Build
cargo build --release --features mcp-server --bin tree-sitter-mcp

# Register with Claude Code
claude mcp add tree-sitter-mcp -- ./target/release/tree-sitter-mcp

This project uses pre-commit to automatically apply linters and formatters before every commit. To ensure your files are automatically formatted and to prevent commit failures due to linting errors, initialize the git hooks in your local repository.

pre-commit install

You can load the plugin directly into your Claude Code session. This method includes a SessionStart hook that automatically builds the tree-sitter-mcp binary on its first use.

Prerequisites for auto-build:

• Rust toolchain (version 1.85.1 or higher)
• A C/C++ compiler (required for tree-sitter grammars)
• Git submodules must be initialized: git submodule update --init --recursive

claude --plugin-dir ./plugins/tree-sitter-mcp

By default, diffsitter compiles tree-sitter grammars statically. If you prefer to use dynamic libraries instead of cloning submodules, you can build the binary with the dynamic-grammar-libs feature enabled. This will look for shared libraries in the user's default library lookup path (e.g., .so on Linux, .dylib on MacOS, or .dll on Windows) following the pattern libtree-sitter-{lang}.{ext}.

cargo build --no-default-features --features dynamic-grammar-libs

The project uses Cargo for building. Because it includes bindings to tree-sitter, you must have a C compiler that supports C99 or later and a C++ compiler that supports C++14 or later.

If you are cloning for the first time, ensure you include submodules to provide the necessary tree-sitter grammars:

git clone --recurse-submodules https://github.com/afnanenayet/diffsitter.git

If you have already cloned the repository, initialize or update the submodules using:

git submodule update --init --recursive