serena

# Serena: Symbol-Level Code Understanding

Navigate and manipulate code at the symbol level using IDE-like semantic analysis powered by Language Server Protocol (LSP).

## How You Can Access Serena

You may have Serena available in one or both of these ways:

**Option 1: Direct MCP Tools** (if configured by your orchestrator)
Check your available tools for:
- `find_symbol`, `find_referencing_symbols` - Symbol lookup
- `rename_symbol`, `replace_symbol_body` - Refactoring
- `insert_after_symbol`, `insert_before_symbol` - Precise insertions
- `onboarding`, `activate_project` - Project understanding
- `write_memory`, `read_memory` - Save context
- And 25+ more LSP-powered tools

If you see these tools, use them directly - they provide full Serena capabilities!

**Option 2: CLI Commands** (always available via execute_command)
You can run serena commands using:
```bash
execute_command("uvx --from git+https://github.com/oraios/serena serena <command>")
```

This skill focuses on CLI usage patterns. If you have direct MCP tools, prefer those for better integration.

## Purpose

The serena skill provides access to Serena, a coding agent toolkit that transforms text-based LLMs into symbol-aware code agents. Unlike traditional text search (ripgrep) or structural search (ast-grep), Serena understands code semantics through LSP integration.

**Key capabilities:**

1. **Symbol Discovery**: Find classes, functions, variables, and types by name across 30+ languages
2. **Reference Tracking**: Discover all locations where a symbol is referenced or used
3. **Precise Editing**: Insert code at specific symbol locations with surgical precision

Serena operates at the **symbol level** rather than the text or syntax level, providing true IDE-like understanding of code structure, scope, and relationships.

## When to Use This Skill

Use the serena skill when you need symbol-level code understanding:

**Code Navigation:**
- Finding where a class, function, or variable is defined
- Discovering all places where a symbol is used (call sites, imports, references)
- Understanding code dependencies and relationships
- Tracing execution flow through function calls

**Code Understanding:**
- Analyzing impact of changes to a function or class
- Understanding inheritance hierarchies and type relationships
- Identifying dead code (symbols never referenced)
- Mapping API usage patterns across a codebase

**Code Refactoring:**
- Renaming symbols while tracking all usage locations
- Adding methods or fields to specific classes
- Inserting error handling after specific function calls
- Modifying all call sites of a deprecated function

**Choose serena over file-search (ripgrep/ast-grep) when:**
- You need to understand symbol semantics (not just text patterns)
- You want to track references across files and modules
- You need precise insertion points based on code structure
- You're working with complex, multi-file codebases

**Still use file-search when:**
- Searching for text patterns, comments, or strings
- Finding todos, security issues, or documentation
- You need faster, simpler pattern matching
- Symbol-level precision isn't required

## Language Support

Serena uses LSP servers for semantic analysis. Most common languages are supported out-of-the-box:
- Python (pyright, jedi)
- JavaScript/TypeScript (typescript-language-server)
- Rust (rust-analyzer)
- Go (gopls)
- Java (jdtls)
- C/C++ (clangd)
- C#, Ruby, PHP, Kotlin, Swift, Scala, and 15+ more

The LSP servers provide symbol information for the language you're working with.

## Core Operations

### 1. Finding Symbols (`find_symbol`)

Locate where a symbol is **defined** in your codebase.

**Note:** All examples below use the short form `serena <command>`. The full command is:
```bash
uvx --from git+https://github.com/oraios/serena serena <command>
```

```python
# Find a class definition
execute_command("uvx --from git+https://github.com/oraios/serena serena find_symbol --name 'UserService' --type class")

# Find a function definition
execute_command("uvx --from git+https://github.com/oraios/serena serena find_symbol --name 'authenticate' --type function")

# Find a variable definition
execute_command("uvx --from git+https://github.com/oraios/serena serena find_symbol --name 'API_KEY' --type variable")
```

**Use cases:**
- Locating the definition of a class before modifying it
- Finding where a function is implemented
- Understanding where constants are defined
- Tracing type definitions in typed languages

**Output format:**
```
File: src/services/user_service.py
Line: 42
Symbol: UserService (class)
Context: class UserService(BaseService):
```

### 2. Finding References (`find_referencing_symbols`)

Discover **all locations** where a symbol is used, imported, or referenced.

```python
# Find all usages of a class
execute_command("serena find_referencing_symbols --name 'UserService'")

# Find all call sites of a function
execute_command("serena find_referencing_symbols --name 'authenticate'")

# Find all reads/writes of a variable
execute_command("serena find_referencing_symbols --name 'API_KEY'")
```

**Use cases:**
- Impact analysis before refactoring
- Finding all call sites of a function
- Tracking API usage across modules
- Identifying unused symbols (zero references)
- Understanding data flow and dependencies

**Output format:**
```
Found 12 references to 'authenticate':

1. src/api/routes.py:34
   authenticate(user_credentials)

2. src/middleware/auth.py:18
   from services import authenticate

3. tests/test_auth.py:56
   mock_authenticate = Mock(spec=authenticate)
...
```

### 3. Precise Code Insertion (`insert_after_symbol`)

Insert code at specific symbol locations with surgical precision.

```python
# Add a method to a class
execute_command("""serena insert_after_symbol --name 'UserService' --type class --code '
    def get_user_by_email(self, email: str) -> Optional[User]:
        return self.db.query(User).filter_by(email=email).first()
'""")

# Insert