Claude Skills Guide

Vite has transformed how developers build modern web applications with its lightning-fast dev server and optimized production builds. However, achieving optimal bundle sizes and build performance often requires deep knowledge of its configuration options, plugins, and best practices. This is where Claude Code becomes invaluable—acting as an intelligent assistant that understands Vite’s ecosystem and can guide you through complex optimization decisions.

This guide presents a practical workflow for using Claude Code to analyze, optimize, and maintain your Vite bundle configuration.

Understanding Your Current Bundle Profile

Before making any optimizations, you need a clear picture of what’s in your bundle. Claude Code can help you generate and interpret bundle analysis reports, making the process much less intimidating.

Start by asking Claude to review your current vite.config.ts:

Analyze my vite.config.ts and explain the current build optimization settings. Identify any missing or suboptimal configurations.

Claude will examine your configuration and provide actionable feedback. For example, it might notice you’re not using code splitting effectively or that your build target could be more specific.

Generating Bundle Analysis Reports

To see exactly what’s contributing to your bundle size, add the rollup-plugin-visualizer to your project:

npm install rollup-plugin-visualizer --save-dev

Then configure it in your vite.config.ts:

import { defineConfig } from 'vite'
import visualizer from 'rollup-plugin-visualizer'

export default defineConfig({
  plugins: [
    visualizer({
      filename: './dist/stats.html',
      open: true,
      gzipSize: true,
      brotliSize: true
    })
  ]
})

Run your production build and open the generated HTML file. You’ll see a visual representation of your bundle, showing which modules contribute the most to size.

Automating Common Optimizations

Claude Code excels at applying systematic optimizations. Here are key areas where it provides immediate value:

Tree Shaking Configuration

Modern JavaScript allows for aggressive tree shaking, but only when your code and dependencies are properly configured. Ask Claude to audit your code:

Review my source code and dependencies for tree shaking issues. Identify any CommonJS modules that prevent optimization and suggest fixes.

Claude will analyze your imports and likely find issues like:

For React applications, a common issue is importing from the full package:

// ❌ Imports everything, prevents tree shaking
import { Button, Input, Modal } from 'ui-library'

// ✅ Named imports enable tree shaking
import { Button } from 'ui-library'
import { Input } from 'ui-library'
import { Modal } from 'ui-library'

Dynamic Imports for Code Splitting

Large applications benefit from splitting code into smaller chunks that load on demand. Claude can identify opportunities for dynamic imports:

Analyze my codebase and suggest routes or components that should use dynamic imports() for code splitting. Show me the before/after code.

Typical candidates include:

Before:

import { HeavyChart } from './charts/heavy-chart'

After:

const HeavyChart = lazy(() => import('./charts/heavy-chart'))

Optimizing Dependencies and Build Settings

External Dependencies Strategy

For large dependencies that rarely change, consider externalizing them in development to speed up builds:

export default defineConfig({
  build: {
    rollupOptions: {
      external: ['react', 'react-dom', 'lodash']
    }
  }
})

However, be strategic—external dependencies must be loaded via CDN or a separate script tag. Claude can help you set up the appropriate HTML injection.

Target and Polyfill Configuration

Setting a specific browser target reduces polyfill bloat:

export default defineConfig({
  build: {
    target: 'es2020',
    cssTarget: 'chrome80'
  }
})

Ask Claude to determine your optimal target based on your supported browsers:

What browsers does my application need to support? Based on this, what should my Vite build target and cssTarget be?

Creating an Optimization Workflow

The real power of Claude Code comes from creating repeatable workflows. Here’s a structured approach:

Step 1: Baseline Measurement

Before any changes, measure your current bundle:

npm run build

Note the output sizes for:

Step 2: Claude-Powered Analysis

Ask Claude to generate a comprehensive optimization report:

Create a detailed optimization report for my Vite project. Include:
1. Current bundle composition analysis
2. Top 5 opportunities for size reduction
3. Specific code changes needed
4. Configuration updates to consider

Step 3: Incremental Changes

Implement changes one at a time, measuring the impact of each:

Step 4: Continuous Monitoring

Add bundle size checks to your CI pipeline to prevent regression:

npm install --save-dev bundle-size-analyzer

Configure a size limit that fails builds exceeding the threshold.

Common Pitfalls to Avoid

Through experience with many Vite projects, Claude can warn you about common mistakes:

  1. Over-optimization: Don’t split too aggressively—it increases HTTP requests and can hurt performance
  2. Premature optimization: Optimize only after measuring, not based on assumptions
  3. Ignoring runtime: Some libraries add significant runtime overhead that code splitting can’t address
  4. Forgetting about CSS: Large CSS bundles can block rendering; consider CSS code splitting

Conclusion

Claude Code transforms Vite bundle optimization from a complex, trial-and-error process into a systematic workflow. By using its ability to analyze code, suggest changes, and explain trade-offs, you can achieve optimal bundle sizes without becoming a Vite internals expert.

Start with a baseline measurement, use Claude to identify opportunities, apply changes incrementally, and monitor continuously. Your users will thank you with faster load times and better performance.

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