/codebase-search

name: codebase-search
description: Search and navigate large codebases efficiently. Use when finding specific code patterns, tracing function calls, understanding code structure, or locating bugs. Handles semantic search, grep patterns, AST analysis.
allowed-tools: [Read, Grep, Glob, Bash]
tags: [codebase-search, grep, code-navigation, pattern-matching]
platforms: [Claude, ChatGPT, Gemini]

Codebase Search

When to use this skill

• Finding specific functions or classes
• Tracing function calls and dependencies
• Understanding code structure and architecture
• Finding usage examples
• Identifying code patterns
• Locating bugs or issues
• Code archaeology (understanding legacy code)
• Impact analysis before changes

Instructions

Step 1: Understand what you're looking for

**Feature implementation**:

• Where is feature X implemented?
• How does feature Y work?
• What files are involved in feature Z?

**Bug location**:

• Where is this error coming from?
• What code handles this case?
• Where is this data being modified?

**API usage**:

• How is this API used?
• Where is this function called?
• What are examples of using this?

**Configuration**:

• Where are settings defined?
• How is this configured?
• What are the config options?

Step 2: Choose search strategy

**Semantic search** (for conceptual questions):

Use when: You understand what you're looking for conceptually
Examples:
- "How do we handle user authentication?"
- "Where is email validation implemented?"
- "How do we connect to the database?"

Benefits:
- Finds relevant code by meaning
- Works with unfamiliar codebases
- Good for exploratory searches

**Grep** (for exact text/patterns):

Use when: You know exact text or patterns
Examples:
- Function names: "def authenticate"
- Class names: "class UserManager"
- Error messages: "Invalid credentials"
- Specific strings: "API_KEY"

Benefits:
- Fast and precise
- Works with regex patterns
- Good for known terms

**Glob** (for file discovery):

Use when: You need to find files by pattern
Examples:
- "**/*.test.js" (all test files)
- "**/config*.yaml" (config files)
- "src/**/*Controller.py" (controllers)

Benefits:
- Quickly find files by type
- Discover file structure
- Locate related files

Step 3: Search workflow

**1. Start broad, then narrow**:

Step 1: Semantic search "How does authentication work?"
Result: Points to auth/ directory

Step 2: Grep in auth/ for specific function
Pattern: "def verify_token"
Result: Found in auth/jwt.py

Step 3: Read the file
File: auth/jwt.py
Result: Understand implementation

**2. Use directory targeting**:

# Start without target (search everywhere)
Query: "Where is user login implemented?"
Target: []

# Refine with specific directory
Query: "Where is login validated?"
Target: ["backend/auth/"]

**3. Combine searches**:

# Find where feature is implemented
Semantic: "user registration flow"

# Find all files involved
Grep: "def register_user"

# Find test files
Glob: "**/*register*test*.py"

# Understand the implementation
Read: registration.py, test_registration.py

Step 4: Common search patterns

**Find function definition**:

# Python
grep -n "def function_name" --type py

# JavaScript
grep -n "function functionName" --type js
grep -n "const functionName = " --type js

# TypeScript
grep -n "function functionName" --type ts
grep -n "export const functionName" --type ts

# Go
grep -n "func functionName" --type go

# Java
grep -n "public.*functionName" --type java

**Find class definition**:

# Python
grep -n "class ClassName" --type py

# JavaScript/TypeScript
grep -n "class ClassName" --type js,ts

# Java
grep -n "public class ClassName" --type java

# C++
grep -n "class ClassName" --type cpp

**Find class/function usage**:

# Python
grep -n "ClassName(" --type py
grep -n "function_name(" --type py

# JavaScript
grep -n "new ClassName" --type js
grep -n "functionName(" --type js

**Find imports/requires**:

# Python
grep -n "from.*import.*ModuleName" --type py
grep -n "import.*ModuleName" --type py

# JavaScript
grep -n "import.*from.*module-name" --type js
grep -n "require.*module-name" --type js

# Go
grep -n "import.*package-name" --type go

**Find configuration**:

# Config files
glob "**/*config*.{json,yaml,yml,toml,ini}"

# Environment variables
grep -n "process\\.env\\." --type js
grep -n "os\\.environ" --type py

# Constants
grep -n "^[A-Z_]+\\s*=" --type py
grep -n "const [A-Z_]+" --type js

**Find TODO/FIXME**:

grep -n "TODO|FIXME|HACK|XXX" -i

**Find error handling**:

# Python
grep -n "try:|except|raise" --type py

# JavaScript
grep -n "try|catch|throw" --type js

# Go
grep -n "if err != nil" --type go

Step 5: Advanced techniques

**Trace data flow**:

1. Find where data is created
   Semantic: "Where is user object created?"

2. Search for variable usage
   Grep: "user\\." with context lines

3. Follow transformations
   Read: Files that modify user

4. Find where it's consumed
   Grep: "user\\." in relevant files

**Find all callsites of a function**:

1. Find function definition
   Grep: "def process_payment"
   Result: payments/processor.py:45

2. Find all imports of that module
   Grep: "from payments.processor import"
   Result: Multiple files

3. Find all calls to the function
   Grep: "process_payment\\("
   Result: All callsites

4. Read each callsite for context
   Read: Each file with context

**Understand a feature end-to-end**:

1. Find API endpoint
   Semantic: "Where is user registration endpoint?"
   Result: routes/auth.py

2. Trace to controller
   Read: routes/auth.py
   Find: Calls to AuthController.register

3. Trace to service
   Read: controllers/auth.py
   Find: Calls to UserService.create_user

4. Trace to database
   Read: services/user.py
   Find: Database operations

5. Find tests
   Glob: "**/*auth*test*.py"
   Read: Test files for ex