Opensrc

A codemode MCP server for fetching and querying dependency source code.

Why?

Traditional MCP exposes tools directly to LLMs. This server uses the codemode pattern: agents write JavaScript that executes server-side, and only results return. Benefits:

• Context efficient - Large source trees stay server-side
• Batch operations - One call to search/read multiple files
• LLMs are better at code - More training data for JS than tool-calling

Installation

npm install -g opensrc-mcp
# or
npx opensrc-mcp

OpenCode Configuration

Add to your OpenCode config (~/.config/opencode/config.json or project opencode.json):

{
  "mcp": {
    "opensrc": {
      "type": "local",
      "command": "npx",
      "args": ["-y", "opensrc-mcp"]
    }
  }
}

Tool

execute

Single tool exposing all operations. Agents write JS that runs server-side; only results return.

// Available in sandbox:
declare const opensrc: {
  // Read operations
  list(): Source[];
  has(name: string, version?: string): boolean;
  get(name: string): Source | undefined;
  files(sourceName: string, glob?: string): Promise<FileEntry[]>;
  tree(sourceName: string, options?: { depth?: number }): Promise<TreeNode>;
  grep(pattern: string, options?: {
    sources?: string[];
    include?: string;
    maxResults?: number;
  }): Promise<GrepResult[]>;
  astGrep(sourceName: string, pattern: string, options?: {
    glob?: string;
    lang?: string | string[];
    limit?: number;
  }): Promise<AstGrepMatch[]>;
  read(sourceName: string, filePath: string): Promise<string>;
  readMany(sourceName: string, paths: string[]): Promise<Record<string, string>>;
  resolve(spec: string): Promise<ParsedSpec>;

  // Mutation operations
  fetch(specs: string | string[], options?: { modify?: boolean }): Promise<FetchedSource[]>;
  remove(names: string[]): Promise<RemoveResult>;
  clean(options?: {
    packages?: boolean;
    repos?: boolean;
    npm?: boolean;
    pypi?: boolean;
    crates?: boolean;
  }): Promise<RemoveResult>;
};

declare const sources: Source[];  // All fetched sources
declare const cwd: string;        // Project directory

Examples:

// List all fetched sources
async () => opensrc.list()

// Fetch npm package (auto-detects version from lockfile)
async () => opensrc.fetch("zod")

// Fetch multiple packages
async () => opensrc.fetch(["zod", "drizzle-orm", "hono"])

// Fetch GitHub repo at specific ref
async () => opensrc.fetch("vercel/[email protected]")

// Fetch from other registries
async () => opensrc.fetch("pypi:requests")
async () => opensrc.fetch("crates:serde")

// Get directory tree
async () => opensrc.tree("zod", { depth: 2 })

// Find TypeScript files
async () => opensrc.files("zod", "**/*.ts")

// Text search
async () => opensrc.grep("parse", { sources: ["zod"], include: "*.ts" })

// AST search (structural pattern matching)
async () => opensrc.astGrep("zod", "function $NAME($$$ARGS)", { glob: "**/*.ts" })

// Read a specific file
async () => opensrc.read("zod", "src/index.ts")

// Read multiple files (supports globs)
async () => opensrc.readMany("zod", ["src/index.ts", "packages/*/package.json"])

// Remove a source
async () => opensrc.remove(["zod"])

// Clean all npm packages
async () => opensrc.clean({ npm: true })

Package Formats

Storage

Sources are stored globally at ~/.local/share/opensrc/ (XDG compliant):

~/.local/share/opensrc/
├── sources.json           # Index of fetched sources
├── packages/              # npm/pypi/crates packages
│   └── zod/
│       ├── src/
│       ├── package.json
│       └── ...
└── repos/                 # GitHub repos
    └── github.com/
        └── vercel/
            └── ai/

Override with $OPENSRC_DIR or $XDG_DATA_HOME.

How It Works

1. Agent calls execute tool with JS code: async () => opensrc.fetch("zod")
2. Code runs in sandboxed vm context with injected opensrc API
3. Server fetches package via opensrc (handles registry lookup, git clone)
4. Only the result returns to agent context

┌─────────────────────────────────────────────────────────────┐
│                      Agent Context                          │
├─────────────────────────────────────────────────────────────┤
│  Tool call: execute({ code: "async () => opensrc.fetch..." })│
│                           ↓                                 │
│  Result: { success: true, source: { name: "zod", ... } }    │
└─────────────────────────────────────────────────────────────┘
                            ↕
┌─────────────────────────────────────────────────────────────┐
│                    opensrc-mcp Server                       │
├─────────────────────────────────────────────────────────────┤
│  Sandbox executes code with injected opensrc API            │
│  Full source tree stays here, never sent to agent           │
└─────────────────────────────────────────────────────────────┘

License

MIT