What I Learned from Digging Into Bolt.new’s Codebase

I spent some time going through the Bolt.new codebase recently, and honestly, it was a deep dive into how these new AI-powered web and app builders actually work.

Learned a lot about the flow, the structure, and how companies are starting to build their own internal versions of these tools. Here’s everything I picked up.

What is Bolt?

If you haven’t heard of it yet:

Bolt is an AI tool that generates full web apps from a single prompt.

You just write something like “Create a todo app,” and it builds out the code for you in seconds. It’s fast, simple, and surprisingly powerful.

Architecture Breakdown

Here’s what I understood by looking at the architecture behind Bolt.

AI Models

Bolt uses Anthropic’s Claude models to generate the code.
To run the code in the browser, it uses Stackblitz’s Webcontainers, which is a solid piece of tech.

The Workflow

This is how the system works behind the scenes:

• You give it a prompt like “Create a todo app”
• That prompt is passed to Claude, which first calls a template endpoint
• This template defines what kind of app you want (like React, Next.js, etc.)
• The response then goes to another endpoint called the builder
• The builder defines the structure — folders, files, architecture
• Once everything is generated, it sends back the final code to you

One simple prompt kicks off the entire process.

Running the App in the Browser

Here’s where it gets even more interesting.

Bolt runs your app directly in the browser using Webcontainers. And from what I’ve seen, here’s what they enable:

• A full dev environment inside the browser
• You can run both frontend and backend code without needing local setup
• You can install npm packages on the fly
• You can connect to external APIs and third-party services

Basically, it gives you a working development environment without touching your terminal.

Deployment

After the app is built, Bolt connects to platforms like Vercel and Netlify, letting you deploy your app instantly. Just click a button, and it’s live.

No extra steps or config files.

Final Thoughts

This is what I pulled out from exploring Bolt’s codebase.

It’s a clean, efficient, and smart way to build apps with the help of AI. And I think this is just the start of a new wave of dev tools that will save time and boost creativity.

What would you build if you had access to something like this?

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