ASTrograph

An MCP server that helps AI agents detect duplicate code before writing it. It provides write and edit tools that compare new code against existing functions in your codebase using AST graph isomorphism — powered by algorithms, not LLM tokens. When a structural duplicate is found, the operation is blocked with a pointer to the existing code. Variable names, formatting, and comments are ignored — if two pieces of code share the same abstract structure, ASTrograph flags them as duplicates.

Installation

Add .mcp.json to your project root:

{
  "mcpServers": {
    "astrograph": {
      "command": "docker",
      "args": [
        "run", "--rm", "-i", "--pull", "missing",
        "--add-host", "host.docker.internal:host-gateway",
        "-v", ".:/workspace",
        "thaylo/astrograph:latest"
      ]
    }
  }
}

The image is multi-arch (amd64, arm64). The codebase is indexed at startup. Metadata is stored outside the project directory (in the user data dir) so it never interferes with your codebase.

To update to a new release:

docker pull thaylo/astrograph:latest

The running version is always visible in the MCP serverInfo.version field on connect.

macOS: ~/Library/Application Support/Claude/claude_desktop_config.json Windows: %APPDATA%\Claude\claude_desktop_config.json

{
  "mcpServers": {
    "astrograph": {
      "command": "docker",
      "args": [
        "run", "--rm", "-i", "--pull", "missing",
        "--add-host", "host.docker.internal:host-gateway",
        "-v", "/absolute/path/to/project:/workspace",
        "thaylo/astrograph:latest"
      ]
    }
  }
}

~/.codex/config.toml:

[mcp_servers.astrograph]
command = "docker"
args = [
  "run", "--rm", "-i", "--pull", "missing",
  "--add-host", "host.docker.internal:host-gateway",
  "-v", "/absolute/path/to/project:/workspace",
  "thaylo/astrograph:latest"
]

~/.config/wmark/.mcp.json (user-level, applies to all projects on macOS):

{
  "mcpServers": {
    "astrograph": {
      "command": "docker",
      "args": [
        "run", "--rm", "-i", "--pull", "missing",
        "--add-host", "host.docker.internal:host-gateway",
        "-v", "/Users:/Users:rw",
        "thaylo/astrograph:latest"
      ]
    }
  }
}

Mounting /Users makes all macOS home paths accessible inside the container unchanged. Call set_workspace with the full host path (e.g. /Users/yourname/project) to index a project.

For Linux, replace /Users:/Users:rw with /home:/home:rw.

pip install .

{
  "mcpServers": {
    "astrograph": {
      "command": "python",
      "args": ["-m", "astrograph.server"],
      "cwd": "/path/to/astrograph"
    }
  }
}

How it works

Your codebase already contains:

# src/math.py
def calculate_sum(a, b):
    return a + b

An AI agent tries to write:

# src/utils.py
def add_numbers(x, y):
    return x + y

ASTrograph detects the duplicate and blocks the write:

BLOCKED: Cannot write - identical code exists at src/math.py:calculate_sum (lines 1-2).
Reuse the existing implementation instead.

Different variable names, identical structure. Source code is converted into labeled directed graphs and compared using Weisfeiler-Leman hashing with VF2 isomorphism verification — all algorithmic, no LLM tokens spent on the search.

Detection types

ASTrograph detects four types of structural duplication:

Near-duplicate detection catches Type-3 clones that exact and pattern detection miss. For example, Flask's TagBytes, TagDateTime, TagTuple, and TagUUID classes share 80%+ identical structure but differ in leaf-level details.

Language support

Python, JavaScript, and TypeScript work out of the box. C, C++, Java, and Go attach to an already-running language server over TCP.

The Docker image bundles Python and JS/TS LSP runtimes. For attach-based languages, expose the language server on a TCP port using socat and configure via your MCP JSON:

{
  "mcpServers": {
    "astrograph": {
      "command": "docker",
      "args": ["run", "--rm", "-i", "--add-host", "host.docker.internal:host-gateway", "-v", ".:/workspace", "thaylo/astrograph:latest"],
      "env": {
        "ASTROGRAPH_CPP_LSP_COMMAND": "tcp://host.docker.internal:2088",
        "ASTROGRAPH_GO_LSP_COMMAND": "tcp://host.docker.internal:2091",
        "ASTROGRAPH_JAVA_LSP_COMMAND": "tcp://host.docker.internal:2089",
        "ASTROGRAPH_C_LSP_COMMAND": "tcp://host.docker.internal:2087"
      }
    }
  }
}

Run lsp_setup(mode='inspect') to see which languages are available and what's missing.

Real-world results

Tested on popular open-source projects:

Exact, pattern, and block findings are verified via VF2 graph isomorphism. Near-duplicates are matched via hierarchy hash prefix similarity (~80% structural identity).

Star History

License

MIT