Serena

MIT

code-searchrefactoringlspjetbrainscoding-agentopen-source

Summary

Semantic code toolkit for coding agents — symbol-level search, editing and refactoring backed by language servers or the JetBrains platform.

Features

Symbol-level code search across a whole project
Find all references to a symbol before changing it
Insert, replace and rename symbols as atomic edits
Language Server Protocol backend covering many languages
Optional JetBrains IDE backend for large codebases
Reads only the symbols an agent needs, saving context
Project-based workflow with per-project configuration

Installation

Set up this MCP server in your favorite AI agent — copy a ready-made configuration below.

Any MCP-compatible agent

Most agents (Claude, Cursor, Windsurf, VS Code, and more) read a standard mcpServers configuration.

Open your agent's MCP configuration file.
Merge the snippet below into it.
Restart the agent — the "Serena" tools will be available.

{
  "mcpServers": {
    "serena-mcp-server": {
      "command": "serena",
      "args": [
        "start-mcp-server",
        "--context=desktop-app"
      ]
    }
  }
}

Claude Code

Add the server with a single CLI command.

claude mcp add serena-mcp-server -- serena start-mcp-server --context=desktop-app

Claude Desktop

Add the server to claude_desktop_config.json (Settings → Developer → Edit Config).

{
  "mcpServers": {
    "serena-mcp-server": {
      "command": "serena",
      "args": [
        "start-mcp-server",
        "--context=desktop-app"
      ]
    }
  }
}

Cursor

{
  "command": "serena",
  "args": [
    "start-mcp-server",
    "--context=ide"
  ]
}

VS Code

{
  "command": "serena",
  "args": [
    "start-mcp-server",
    "--context=ide"
  ]
}

Claude Code — register Serena globally, scoped to the current working directory

{
  "command": "claude",
  "args": [
    "mcp",
    "add",
    "--scope",
    "user",
    "serena",
    "--",
    "serena",
    "start-mcp-server",
    "--context",
    "claude-code",
    "--project-from-cwd"
  ]
}

One-time install step (then run `serena init`)

{
  "command": "uv",
  "args": [
    "tool",
    "install",
    "-p",
    "3.13",
    "serena-agent"
  ]
}

Description

Serena gives a coding agent the tools an IDE gives a developer. Rather than grepping for strings and rewriting files by line number, an agent connected to Serena works at the level of symbols: find a class or function by name, list every reference to it, read only the body it needs, insert a method after another one, or rename a symbol across the whole project as a single atomic operation.

The semantic layer comes from real language tooling. By default Serena runs Language Server Protocol servers — the same ones that power editor autocomplete — which keeps it free and open source across a wide range of languages. Alternatively it can be driven by a JetBrains IDE backend, which trades the extra setup for the deeper indexing JetBrains does on large codebases.

The practical payoff is token efficiency on big repositories. Loading a 4,000-line file to change one method wastes most of the context window; asking for that one symbol does not. This matters most where naive agents struggle: multi-file renames, moves, and reference lookups that would otherwise take a dozen careful, error-prone steps.

Serena is MIT-licensed, written in Python and distributed as the serena-agent tool via uv. It is a stdio MCP server, so it works with Claude Code, Claude Desktop, Codex and any MCP-capable IDE. The maintainers explicitly ask you to install from source rather than from plugin marketplaces, which carry outdated launch commands. Note that setup is a two-step process — install the tool, then run serena init — and that some languages need their language server installed separately.

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