CodeGraph

A code-structure index and query engine for large repositories, built as an AOT-compiled .NET sidecar. It parses a project with tree-sitter, stores symbols/edges in SQLite, and exposes a graph query surface (search, callers, callees, call paths, context packs) over a length-prefixed MessagePack IPC protocol and a dedicated MCP stdio executable.

Extracted from OpenCowork, where it is consumed as a git submodule.

Layout

Project	Purpose
OpenCowork.Worker.Runtime	Shared worker runtime: IPC transport, dispatch, host builder, SystemModule. Single source of truth for the worker protocol.
OpenCowork.CodeGraph.Core	The engine — scanning, extraction, storage, traversal, query, and the codegraph/* module + MCP tool surface.
OpenCowork.CodeGraph.Worker	Thin AOT executable hosting SystemModule + CodeGraphModule.
OpenCowork.CodeGraph.Mcp	Dedicated AOT executable exposing the CodeGraph tools as a standard MCP stdio server.
OpenCowork.CodeGraph.Tests	xUnit suite over Core.

Build

dotnet build CodeGraph.slnx -c Release
dotnet test  CodeGraph.slnx -c Release

AOT publish of the sidecar binary:

dotnet publish OpenCowork.CodeGraph.Worker/OpenCowork.CodeGraph.Worker.csproj \
  -c Release -r osx-arm64 -o out /p:PublishAot=true /p:StripSymbols=true

dotnet publish OpenCowork.CodeGraph.Mcp/OpenCowork.CodeGraph.Mcp.csproj \
  -c Release -r osx-arm64 -o out-mcp /p:PublishAot=true /p:StripSymbols=true

Requires the .NET 10 SDK. Supported RIDs: osx-arm64, osx-x64, win-x64, win-arm64, linux-x64, linux-arm64.

Running

# Self-test: proves SQLite FTS5 + the tree-sitter binding in this binary, then exits.
./OpenCowork.CodeGraph.Worker

# IPC worker mode.
./OpenCowork.CodeGraph.Worker --ipc <endpoint>

MCP over stdio

OpenCowork.CodeGraph.Mcp is a separate executable dedicated to standard MCP stdio. It uses the official MCP C# SDK, keeps stdout reserved for JSON-RPC, and exits when the client closes stdin.

./OpenCowork.CodeGraph.Mcp --project /absolute/path/to/project

--project is optional. The default project is resolved in this order: --project, CODEGRAPH_PROJECT_PATH, then the process working directory. A tool call may still override it with its projectPath argument.

Example MCP client configuration:

{
  "mcpServers": {
    "codegraph": {
      "command": "/absolute/path/to/OpenCowork.CodeGraph.Mcp",
      "args": ["--project", "/absolute/path/to/project"]
    }
  }
}

The advertised tools honor CODEGRAPH_MCP_TOOLS; when it is unset, the default MCP surface contains only codegraph_explore.

npm / npx package

The independent npm project under npm/ packages the framework-dependent .NET MCP server with native tree-sitter assets for macOS, Linux, and Windows on x64/arm64. The Node launcher selects the current platform assets and starts the server over stdio; it does not rewrite the MCP as JavaScript. End users need Node.js 18 or later and the .NET 10 runtime.

Run the published package without installing it globally:

npx -y @aidotnet/codegraph-mcp@1.0.0 \
  --project /absolute/path/to/project

Example MCP client configuration:

{
  "mcpServers": {
    "codegraph": {
      "command": "npx",
      "args": [
        "-y",
        "@aidotnet/codegraph-mcp@1.0.0",
        "--project",
        "/absolute/path/to/project"
      ]
    }
  }
}

Build, inspect, and publish the npm package from this repository:

npm run build --prefix npm
npm run pack --prefix npm
npm publish artifacts/npm/tarballs/aidotnet-codegraph-mcp-1.0.0.tgz \
  --access public --otp <one-time-code>

For CI publishing, create a granular npm access token with read/write access to @aidotnet/codegraph-mcp and Bypass 2FA enabled, save it as the repository secret NPM_TOKEN, and run the Publish npm MCP workflow. Release tags must match all .NET, npm, and MCP manifest versions.

NuGet / dnx package

The MCP project packs as both a DotnetTool and an McpServer, including its MCP registry manifest and cross-platform tree-sitter native assets:

dotnet pack OpenCowork.CodeGraph.Mcp/OpenCowork.CodeGraph.Mcp.csproj -c Release
dnx OpenCowork.CodeGraph.Mcp@1.0.0 --project /absolute/path/to/project

The .nupkg is written to artifacts/packages. To publish it after configuring a NuGet API key:

dotnet nuget push artifacts/packages/OpenCowork.CodeGraph.Mcp.1.0.0.nupkg \
  --source https://api.nuget.org/v3/index.json \
  --api-key "$NUGET_API_KEY"

For CI publishing, add NUGET_API_KEY as a repository secret and run the Publish NuGet MCP workflow. Release tags must match the project and manifest version.

tree-sitter grammars

The engine resolves grammar shared libraries at startup from a grammars/ directory beside the executable, or from OPEN_COWORK_CODEGRAPH_GRAMMARS_DIR. Grammars are not committed here — they come from the TreeSitter.DotNet NuGet package's RID-specific native assets. The consuming application is responsible for staging them next to the published binary (OpenCowork does this in scripts/publish-native-worker.mjs via scripts/codegraph-grammar-manifest.mjs).

Consuming from OpenCowork

OpenCowork.Worker.Runtime is shared by two binaries: the OpenCowork.CodeGraph.Worker in this repo (via ProjectReference) and OpenCowork's OpenCowork.Native.Worker (which source-links Runtime/, Hosting/, Contracts/ and Modules/SystemModule.cs directly, so both speak an identical protocol). Renaming or moving anything under those paths is a cross-repo change — update OpenCowork's OpenCowork.Native.Worker.csproj in the same pass.

Conventions

Global namespace, all-internal types, InternalsVisibleTo between the assemblies. Sources are heavily commented with design rationale; read the header block of a file before changing it.

License

MIT — see LICENSE.