ASTrograph

An MCP server that stops AI agents from writing duplicate code. It offers improved write and edit tools that compare new code against every function already in your codebase using AST graph isomorphism, blocking the operation when a structural duplicate is found. Variable names, formatting, and comments are irrelevant — if two pieces of code have the same abstract structure, ASTrograph treats 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.

Claude Desktop

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

~/.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"
]

wmark

~/.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.

Without Docker

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 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. Text similarity is not involved.

Detection types

ASTrograph detects four types of structural duplication:

Type	What it catches	How it works
Exact	Identical AST structure with renamed variables or different formatting	WL hash identity + VF2 graph isomorphism verification
Pattern	Same control flow with different operators or constants	Operator-normalized graph hashing
Block	Duplicate inner blocks (for/if/while/try) within functions	Block-level AST extraction + hash matching
Near-duplicate	~80% structural similarity — copy-paste-modify patterns	Hierarchy hash prefix matching at 4/5 depth levels

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.

Language	Versions	Mode	Default endpoint
Python	3.11 -- 3.14	bundled	pylsp
JavaScript	ES2021+, Node 20/22/24 LTS	bundled	typescript-language-server --stdio
TypeScript	TypeScript 5.x, Node 20/22/24 LTS	bundled	typescript-language-server --stdio
Go	1.21 -- 1.25	attach	tcp://127.0.0.1:2091
C	C11, C17, C23	attach	tcp://127.0.0.1:2087
C++	C++17, C++20, C++23	attach	tcp://127.0.0.1:2088
Java	11, 17, 21, 25	attach	tcp://127.0.0.1:2089

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"
      }
    }
  }
}

Language	Env var	Socat bridge example
C	ASTROGRAPH_C_LSP_COMMAND	socat TCP-LISTEN:2087,reuseaddr,fork EXEC:clangd
C++	ASTROGRAPH_CPP_LSP_COMMAND	socat TCP-LISTEN:2088,reuseaddr,fork EXEC:clangd
Java	ASTROGRAPH_JAVA_LSP_COMMAND	socat TCP-LISTEN:2089,reuseaddr,fork EXEC:jdtls
Go	ASTROGRAPH_GO_LSP_COMMAND	socat TCP-LISTEN:2091,reuseaddr,fork EXEC:"gopls serve"
Python	ASTROGRAPH_PY_LSP_COMMAND	(bundled, override if needed)
JS	ASTROGRAPH_JS_LSP_COMMAND	(bundled, override if needed)
TS	ASTROGRAPH_TS_LSP_COMMAND	(bundled, override if needed)

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

Real-world results

Tested on popular open-source projects:

Project	Language	Files	Code Units	Duplicates Found
Redis	C	208	18,272	556 groups
TypeORM	TypeScript	492	7,107	511 groups
Express.js	JavaScript	141	3,866	468 groups
nlohmann/json	C++	488	9,103	959 groups
Gin	Go	99	1,557	141 groups
Flask	Python	24	910	48 groups
Spring PetClinic	Java	47	270	17 groups

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