serena

Serena is a toolkit that gives AI coding agents the kind of code-understanding capabilities normally found in professional IDEs (Integrated Development Environments). The problem it solves is that AI agents working with code typically rely on basic text search and line-number references, which become slow and error-prone in large codebases. Serena instead gives agents "semantic" tools — meaning they understand code at the level of symbols (functions, classes, variables) and their relationships, rather than just raw text.

In practice this means an AI agent using Serena can do things like rename a function across an entire codebase in one step, find every place a method is called, or navigate between related symbols — operations that would otherwise require many careful steps with basic search tools.

Serena works through MCP (Model Context Protocol), a standard that lets it plug into AI clients like Claude Code, GitHub Copilot, Cursor, and others. Under the hood it uses LSP (Language Server Protocol) — the same technology code editors use to understand syntax — supporting over 40 programming languages. There is also a paid JetBrains IDE plugin for deeper integration.

You would use Serena if you want your AI coding assistant to be significantly more effective on large or complex projects, by giving it real IDE-grade tools rather than text search. It is written in Python.