LXR Code Browser MCP Server

MCP server for cross-referenced code navigation across the EIC codebase, powered by the LXR engine at BNL.

Provides AI assistants with structured access to 55+ indexed EIC repositories — identifier cross-references, ripgrep search, source file reading, and directory browsing.

Browse the code directly: https://eic-code-browser.sdcc.bnl.gov/lxr/source

Tools

Tool	Description
lxr_ident	Find where a symbol (class, function, variable) is defined and referenced across all repos
lxr_search	Ripgrep-powered regex/text search across the entire codebase
lxr_source	Read source files with line numbers and optional range filtering
lxr_list	Browse directory contents and repository structure

Usage

As a stdio MCP server

pip install -r requirements.txt
python lxr_mcp_server.py

With Claude Code

1. Clone the repo and install dependencies:

git clone https://github.com/BNLNPPS/lxr-mcp-server.git
pip install -r lxr-mcp-server/requirements.txt

2. Add to your Claude Code MCP config (~/.claude/settings.json or project .mcp.json):

{
  "mcpServers": {
    "lxr": {
      "command": "python",
      "args": ["/path/to/lxr-mcp-server/lxr_mcp_server.py"]
    }
  }
}

3. Restart Claude Code.

Network access

The LXR code browser at eic-code-browser.sdcc.bnl.gov is accessible from inside the BNL network. From outside BNL, an SSH tunnel works (same approach as for remote SSH access to BNL machines). Set LXR_BASE_URL to point at your tunnel endpoint.

Environment variables

Variable	Default	Description
LXR_BASE_URL	https://eic-code-browser.sdcc.bnl.gov/lxr	LXR instance URL
LXR_CONFIG	lxr_config.yaml (next to server script)	Path to config file

Examples

Find all definitions of a C++ class:

lxr_ident(symbol="CalorimeterHitDigi", definitions_only=True)

Search for a pattern in header files:

lxr_search(pattern="InitPlugin", file_pattern="*.cc", max_results=20)

Read specific lines of a source file:

lxr_source(path="EICrecon/src/algorithms/calorimetry/CalorimeterHitDigi.h", start_line=40, end_line=60)

List top-level repositories:

lxr_list(path="")

Architecture

Currently parses HTML from the LXR web interface. A future version could run directly on the LXR host and query the cross-reference index natively for better performance.

License

Apache 2.0 — see LICENSE.