Agent Skills: Codebase Explorer

Codebase Explorer

Instructions

When to Invoke This Skill

• Need to find where specific functionality is implemented
• Understanding codebase structure before making changes
• Locating files related to a feature or bug
• Discovering architectural patterns in the project
• Finding examples of similar functionality
• Understanding dependencies between components

Exploration Strategies

1. Top-Down Exploration (Start Broad)

Use when: You know the general area but not specific files.

Approach:

1. Start with project structure overview
2. Identify likely directories
3. Find entry points
4. Trace execution flow

2. Bottom-Up Exploration (Start Specific)

Use when: You know specific terms, functions, or classes.

Approach:

1. Search for specific strings
2. Find definitions
3. Trace usages
4. Understand context

3. Pattern-Based Exploration

Use when: Looking for similar implementations.

Approach:

1. Find one example
2. Search for similar patterns
3. Identify conventions
4. Apply understanding

Tools and Techniques

Using Glob to Find Files

Find by pattern:

# All Python files
**/*.py

# All Vue components
frontend/src/components/**/*.vue

# All test files
**/test_*.py
src/tests/**/*.py

# Specific area
src/legion/**/*.py

# Configuration files
**/*.json
**/*.md

Find entry points:

# Main entry
main.py
**/main.py

# Server files
**/server.py
**/*_server.py

# Index files
**/index.html
**/index.js

Using Grep to Search Code

Find function definitions:

# Python functions
def <function_name>

# Python classes
class <ClassName>

# JavaScript/TypeScript functions
function <functionName>
const <functionName> =

# Vue components
export default {

Find usages:

# Where is function called?
<function_name>(

# Where is class instantiated?
<ClassName>(

# Where is import used?
from .* import .*<name>
import .* from

Find by functionality:

# WebSocket code
websocket
WebSocket

# Database operations
SELECT |INSERT |UPDATE |DELETE

# API endpoints
@app\.route|@router\.(get|post|put|delete)

# Error handling
try:|except |raise |throw

Find configuration:

# Environment variables
os\.environ|process\.env

# Configuration files
config|settings|\.env

Exploration Workflows

Workflow 1: Finding Feature Implementation

Goal: Find where user authentication is implemented.

Steps:

1. Search for keywords:

   grep -r "auth" --include="*.py"
   grep -r "login" --include="*.py"
   

2. Find files:

   **/*auth*.py
   **/*login*.py
   

3. Read relevant files:

   • Look for class/function definitions
   • Identify main entry points
   • Trace dependencies

4. Find usages:

   grep "authenticate(" **/*.py
   grep "login(" **/*.py
   

5. Understand flow:

   • API endpoint → Business logic → Data layer
   • Frontend → API → Backend

Workflow 2: Understanding Architecture

Goal: Understand how sessions work.

Steps:

1. Find session-related files:

   **/*session*.py
   

2. Read main files:

   • Start with core classes (SessionManager, etc.)
   • Understand data structures
   • Identify key methods

3. Find related components:

   grep "SessionManager" **/*.py
   grep "session_id" **/*.py
   

4. Trace data flow:

   • How sessions are created
   • Where session state is stored
   • How sessions are accessed

5. Map dependencies:

   • What does session management depend on?
   • What depends on session management?

Workflow 3: Finding Similar Implementation

Goal: Want to add new API endpoint, find examples.

Steps:

1. Find API endpoint definitions:

   grep "@app\.route\|@router\.(get|post)" **/*.py
   

2. Read example endpoint:

   • Understand parameter handling
   • See error handling pattern
   • Note response format

3. Find related patterns:

   grep "jsonify\|JSONResponse" **/*.py
   

4. Identify conventions:

   • Request validation approach
   • Error response format
   • Success response format

Workflow 4: Debugging Error Location

Goal: Error mentions "WebSocketManager", find where it's defined.

Steps:

1. Find class definition:

   grep "class WebSocketManager" **/*.py
   

2. Read the class:

   • Understand responsibilities
   • Note key methods
   • See error handling

3. Find usages:

   grep "WebSocketManager(" **/*.py
   

4. Trace error path:

   • Where is error raised?
   • What triggers it?
   • How to fix?

Understanding Project Structure

Typical Python Backend Structure

src/
├── server.py             # HTTP server, API endpoints
├── coordinator.py        # Orchestration, coordination
├── models.py             # Data models, entities
├── services/             # Business logic services
├── storage.py            # Persistence layer
└── tests/                # Unit tests
    ├── test_*.py
    └── conftest.py

Typical Frontend Structure

frontend/src/
├── components/            # UI components
│   ├── layout/           # Layout components
│   ├── views/            # Page-level views
│   └── common/           # Reusable components
├── stores/               # State management
├── router/               # Route definitions
├── composables/          # Reusable composition functions
└── utils/                # Helper functions

Reading Code Effectively

1. Start with Entry Points

Backend:

• main.py - Application entry
• web_server.py - API endpoints
• Route handlers - Request processing

Frontend:

• index.html - HTML entry
• main.js - JavaScript entry
• App.vue - Root component
• router/index.js - Route definitions

2. Follow the Flow

Request Flow (Backend):

API Endpoint
   ↓
Request Validation
   ↓
Business Logic (Manager/Coordinator)
   ↓
Data Layer (Storage)
   ↓
Response Formation

Component Flow (Frontend):

User Action
   ↓
Component Event Handler
   ↓
Store Action
   ↓
API Call (or Local State Update)
   ↓
Store State Update
   ↓
Reactive UI Update

3. Identify Patterns

Common Patterns to Recognize:

• Factory pattern (create objects)
• Observer pattern (event handling)
• Repository pattern (data access)
• Coordinator pattern (orchestration)
• Component composition (UI building)

4. Understand Dependencies

Import Statements Tell Story:

from .user_service import UserService
from .project_service import ProjectService
from .storage import Database

This file coordinates multiple services.

Circular Dependencies: If A imports B and B imports A, there's likely architectural issue.

Common Codebase Questions

"Where is X implemented?" → Search for class/function definition: grep "def X\|class X"

"How is X used?" → Search for usages: grep "X("

"What files handle Y functionality?" → Search for keywords: grep -r "keyword" --include="*.py"

"What are the API endpoints?" → Search for route decorators: grep "@app\.route\|@router\."

"Where is data stored?" → Find storage classes, look for file I/O operations

"How do frontend and backend communicate?" → Find API calls in frontend, match to endpoints in backend

Examples

Example 1: Find user creation logic

1. Search for "create_user"
   grep "def create_user" **/*.py

2. Found in: src/coordinator.py and src/services/user_service.py

3. Read the create_user method:
   - Validates input
   - Calls service layer
   - Persists to storage

4. Understand flow:
   API endpoint → Coordinator → Service → Storage

Example 2: Find frontend component for item list

1. Find related components:
   frontend/src/components/**/*List*.vue

2. Look for list-related:
   ItemList.vue, ItemCard.vue

3. Read ItemList.vue:
   - Uses state store
   - Renders ItemCard for each item
   - Handles selection and filtering

4. Check store:
   frontend/src/stores/items.js
   - Items stored in Map
   - CRUD operations defined

Example 3: Understand WebSocket message handling

1. Find WebSocket code:
   grep "websocket\|WebSocket" **/*.py

2. Found: server.py has WebSocket handling

3. Read WebSocket handler:
   - Manages connections
   - Routes messages
   - Broadcasts updates

4. Find message handlers:
   grep "handle.*message" src/server.py

5. Trace message flow:
   WebSocket → Handler → Store/Coordinator → Response

Example 4: Find how authentication works

1. Search for auth-related code:
   grep -r "auth" **/*.py

2. Found in:
   - src/middleware/auth.py (middleware)
   - src/services/auth_service.py (logic)
   - src/models.py (user model)

3. Read auth middleware:
   - Extracts token from request
   - Validates against service
   - Sets user context

4. Understand flow:
   Request → Middleware → Token validation →
   User lookup → Context set → Handler executes