# Sem (MCP server)

> Sem is an MCP server that adds developer tools to AI assistants such as Claude Desktop, Claude Code and Cursor. Entity-level code intelligence: semantic diff, impact analysis, blame, and context for AI agents. It has 3,397 GitHub stars, is released under the Apache-2.0 license and runs locally with npx -y @ataraxy-labs/sem.

Part of the Ataraxy Labs stack: agent-native infrastructure for software development. See also: weave (entity-level git merge driver) · inspect (semantic code review) · opensessions (tmux sidebar for coding agents). Read the manifesto: · Essays: · LLMs:

## Key facts

| Fact | Value |
|---|---|
| Repository | https://github.com/Ataraxy-Labs/sem |
| GitHub stars | 3,397 |
| License | Apache-2.0 |
| Language | Rust |
| Transport | stdio |
| Packages | npm: @ataraxy-labs/sem |
| Remote URL | none |
| Needs API key | no |
| Official | yes |
| Works with | Claude Desktop, Claude Code, Cursor, VS Code |
| Category | Developer tools |
| Latest release | v0.27.0 (Oct 4, 2026) |
| Last commit | Oct 7, 2026 |
| MCP registry name | io.github.Ataraxy-Labs/sem |

## Install

### Claude Desktop (claude_desktop_config.json)

```json
{
  "mcpServers": {
    "sem": {
      "command": "npx",
      "args": [
        "-y",
        "@ataraxy-labs/sem"
      ]
    }
  }
}
```

Settings > Developer > Edit Config. macOS: ~/Library/Application Support/Claude/, Windows: %APPDATA%\Claude\. Restart Claude Desktop afterwards.

### Claude Code

```sh
claude mcp add --transport stdio sem -- npx -y @ataraxy-labs/sem
```

### Cursor (.cursor/mcp.json)

```json
{
  "mcpServers": {
    "sem": {
      "type": "stdio",
      "command": "npx",
      "args": [
        "-y",
        "@ataraxy-labs/sem"
      ]
    }
  }
}
```

Project file; use ~/.cursor/mcp.json to enable it in every project.

### VS Code (.vscode/mcp.json)

```json
{
  "servers": {
    "sem": {
      "type": "stdio",
      "command": "npx",
      "args": [
        "-y",
        "@ataraxy-labs/sem"
      ]
    }
  }
}
```

Config formats checked against the official docs on 2026-10-07.

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