I Tested Bolt.new, Replit Agent, and Cline for 2 Weeks - Here's What Actually Works

I've been building side projects and prototypes for years, and I've used everything from vanilla VS Code to GitHub Copilot. But lately, the AI coding landscape has shifted dramatically. Three tools keep coming up in conversations: Bolt.new, Replit Agent, and Cline. I decided to put all three through their paces for two solid weeks, building real projects with each one. Here's my unfiltered experience.

Quick Comparison Table

Feature	Bolt.new	Replit Agent	Cline
Pricing	Free tier (limited), Pro $20/mo	Free tier (limited), Hacker $25/mo, Pro $50/mo	Free (bring your own API key), costs vary by usage
Installation	Web-based, zero setup	Web-based, zero setup	VS Code extension, requires API key setup
Language Support	JavaScript/TypeScript, React, Next.js, basic Python	50+ languages, full stack	Any language VS Code supports
Deployment	One-click to Netlify/Cloudflare	Built-in hosting with URL	Manual (you handle it)
Best For	Quick prototypes, frontend-heavy apps	Full-stack apps, learning, quick deployments	Complex projects, existing codebases, power users
Context Window	Limited (around 8k tokens)	Moderate (around 16k tokens)	Large (depends on model, up to 200k tokens)
Autonomy Level	Low-medium (guided, step-by-step)	Medium-high (semi-autonomous)	High (fully autonomous with approval)
Model	Proprietary, fine-tuned	Proprietary, fine-tuned	Bring your own (GPT-4, Claude, etc.)

My Testing Setup

I built three projects with each tool:

1. A simple todo app - to test basic CRUD and UI
2. A markdown blog with authentication - to test routing, databases, and auth
3. A real-time chat app with WebSockets - to test complex state management and real-time features

I also tried migrating an existing Node.js/Express project I had lying around to see how each handled legacy code.

Bolt.new: The Fastest Path to "It Works"

First Impressions

Bolt.new is the most polished of the three. You land on a clean web interface, type what you want, and it starts building immediately. No account needed to try it (though you'll hit limits fast without paying). The UI is beautiful - it shows you a live preview of your app as it's being built, which is incredibly satisfying.

Building the Todo App

I typed: "Build a todo app with React, dark mode, local storage persistence, and the ability to edit and delete todos."

Bolt.new started coding immediately. It created a single-file React app with inline styles. The whole thing took about 30 seconds. The live preview updated as it wrote code - I could literally watch the UI appear piece by piece.

What went well:

• The result was clean, functional, and looked decent
• Local storage worked out of the box
• Dark mode toggle was smooth

What went wrong:

• It couldn't add dependencies on its own. When I asked for "use UUIDs for IDs," it tried to use a library but couldn't install it
• The code was all in one file, which is fine for a demo but not for real projects
• When I asked for a refactor into multiple files, it got confused and broke things

The Markdown Blog

This is where Bolt.new started showing cracks. I asked for a Next.js blog with Markdown support and GitHub authentication.

It generated a nice-looking Next.js app with a basic markdown parser. The GitHub auth setup was impressive - it created the OAuth flow correctly. But then I hit the wall.

The problems:

• Bolt.new has a hard time understanding existing project structure. After the initial generation, making changes became increasingly unreliable
• It kept suggesting changes that broke other parts of the app
• The context window is small - after about 20 messages, it started forgetting what the project was about
• There's no way to edit files manually. If the AI messes up, you're stuck asking it to fix itself

Real-Time Chat

I didn't even bother. Bolt.new's architecture is fundamentally limited for real-time apps. It generates static or server-rendered pages, but WebSocket support requires backend configuration that it can't handle well. I tried and got a half-baked Socket.io implementation that crashed on refresh.

Pricing Reality

The free tier is basically a demo. You get maybe 10-15 generations before you hit limits. Pro at $20/month is reasonable if you're building simple frontends, but you'll quickly outgrow it.

Who is Bolt.new For?

Perfect for: Non-developers who want to prototype a landing page or a simple React app. Designers who need to validate an idea quickly. Beginners who want to see what building feels like.

Not for: Anyone building production apps, complex backends, or anything that needs maintenance.

Replit Agent: The Swiss Army Knife

First Impressions

Replit Agent feels like Bolt.new's older, more experienced sibling. The interface is less polished - it's essentially Replit's online IDE with an AI agent that can do things on its own. You get a real file system, a terminal, and the ability to edit code manually. This is huge.

Building the Todo App

Same prompt: "Build a todo app with React, dark mode, local storage persistence, and the ability to edit and delete todos."

Replit Agent took a different approach. It created a proper project structure with separate files for components, styles, and logic. It installed dependencies automatically. The live preview worked, though it was slower than Bolt.new's.

What went well:

• The code was well-structured from the start
• I could open any file and edit it manually if I didn't like what the AI did
• It added proper error handling and edge cases without being asked
• The terminal was accessible - I could run npm commands, check logs, debug

What went wrong:

• The agent sometimes got stuck in loops, repeatedly trying the same broken solution
• It occasionally deleted files or overwrote my manual changes without asking
• The UI is less intuitive than Bolt.new - more powerful, but harder to learn

The Markdown Blog

This is where Replit Agent shined. I asked for the same Next.js blog with Markdown and GitHub auth.

The agent:

1. Created a Next.js project with proper structure
2. Set up next-auth for GitHub authentication
3. Created a markdown parser with gray-matter for frontmatter
4. Added a database (I chose SQLite via Prisma)
5. Generated admin pages for creating and editing posts

The magic moment: When I asked it to add a "share on Twitter" button to each post, it not only added the button but also generated Open Graph metadata and a proper sitemap. It understood the context.

The frustration: The agent is autonomous, which means it sometimes does things you didn't ask for. I had to tell it "stop adding features" several times. It also has a tendency to refactor your code without permission, which can break things.

Real-Time Chat

I built this with Replit Agent and it mostly worked. It set up a Node.js server with Express and Socket.io, created a React frontend with proper state management, and deployed it to Replit's built-in hosting.

The problems:

• The agent struggled with WebSocket connection handling. It took about 10 iterations to get reconnection logic working
• Deployment was confusing - Replit's hosting has quirks with WebSocket support
• The final product worked but was bloated. The agent added unnecessary libraries and abstractions

Pricing Reality

The free tier gives you 10 agent runs per month. The Hacker plan at $25/month is what you'll actually need. The Pro plan at $50/month adds more compute and priority access. For serious use, Hacker is the minimum.

Who is Replit Agent For?

Perfect for: Solo developers building full-stack apps quickly. Students learning web development. Anyone who wants a balance between AI assistance and manual control.

Not for: Teams (collaboration is weak), enterprise projects, or anyone who needs fine-grained control over infrastructure.

Cline: The Power User's Choice

First Impressions

Cline is different. It's not a web app - it's a VS Code extension. You bring your own API key (OpenAI, Anthropic, or any OpenAI-compatible provider). This means you pay for what you use, and you can choose your model. I used GPT-4 for most of my testing, but also tried Claude 3.5 Sonnet.

The setup is more involved than the other two. You need:

1. VS Code installed
2. The Cline extension from the marketplace
3. An API key from your provider of choice

Once set up, Cline lives in your VS Code sidebar. You give it tasks, and it reads/writes files, runs terminal commands, and even opens browsers to test things.

Building the Todo App

Same prompt. Cline asked a clarifying question first: "Should I use React with TypeScript or plain JavaScript? Do you want any testing framework?"

This was a good sign. It wanted to understand the requirements before starting.

The process:

• It created the project from scratch, initializing with Vite + React + TypeScript
• It set up proper file structure: components, hooks, utils, styles
• It wrote tests alongside the implementation (I didn't ask for this)
• It installed dependencies as needed

What went well:

• The code was production-quality. Proper TypeScript types, error boundaries, accessibility attributes
• It handled edge cases I hadn't thought of (empty state, loading state, error state)
• I could review every change before it was applied (Cline asks for approval before writing files or running commands)
• The approval system means I never lost control

What went wrong:

• It's slower because of the approval process. Each file write requires confirmation
• The initial setup cost me about $2 in API calls for a simple todo app
• It doesn't have a built-in preview. I had to run npm run dev manually

The Markdown Blog

This is where Cline absolutely destroyed the competition. I gave it the same requirements, and it built something I would have been proud to ship to production.

The key difference: Cline understands existing codebases. It read my existing project structure before making changes. When I asked for changes later, it didn't break anything because it had full context.

Specific examples:

• It set up proper Next.js App Router with server components where appropriate
• It created a Prisma schema with proper relations (User, Post, Comment)
• It implemented GitHub OAuth with next-auth, including database sessions
• It added rate limiting to the auth endpoints
• It created a proper admin dashboard with CRUD for posts
• It even added SEO metadata and a sitemap

The cost: Building this blog cost about $8 in API calls. That's expensive compared to the flat fees of Bolt.new or Replit Agent. But the quality was significantly higher.

Real-Time Chat

This was the real test. Cline handled it beautifully.

What it did:

1. Set up a Node.js server with TypeScript
2. Used Socket.io with proper connection handling
3. Created a React frontend with a custom hook for WebSocket management
4. Implemented reconnection logic with exponential backoff
5. Added typing indicators, online status, and message history
6. Set up Redis for message persistence across server restarts

The process took about 45 minutes (with approvals) and cost roughly $5 in API calls. The final product was production-ready, with proper error handling, logging, and even a Dockerfile for deployment.

The Migration Test

I threw my existing Node.js/Express project at Cline. This was the real test.

Bolt.new couldn't even open my project (it's web-based, no file system access).
Replit Agent could import it but struggled with the existing structure.

Cline read the entire project, understood the architecture, and helped me:

1. Add TypeScript gradually
2. Implement proper error handling middleware
3. Add tests for the API endpoints
4. Refactor the routing into a cleaner structure

It never broke anything because it always asked before making changes. This is the killer feature for anyone working on real projects.

Pricing Reality

Cline is free to install. You pay for API usage. My two weeks of heavy testing cost about $60 in API calls. For a professional developer, that's cheap. For a hobbyist, the flat fees of Bolt.new or Replit Agent might be more appealing.

Pro tip: Use Claude 3.5 Sonnet for coding tasks. It's cheaper than GPT-4 and often produces better code. I switched halfway through and saved about 30% on costs.

Who is Cline For?

Perfect for: Professional developers. Anyone working on existing codebases. Teams that need AI assistance without losing control. Projects that need to be production-ready.

Not for: Beginners who just want to see if an idea works. Anyone who doesn't want to deal with API keys and costs. People who need a one-click deploy solution.

The Verdict: Which One Should You Use?

After two weeks of intense testing, here's my honest take:

For Quick Prototypes: Bolt.new

If you want to see if an idea works in 10 minutes, Bolt.new is the best. It's fast, polished, and requires zero setup. Just don't expect to build anything you'd ship to production.

For Learning and Full-Stack Apps: Replit Agent

If you're building a full-stack app and want to learn as you go, Replit Agent is the sweet spot. It's powerful enough to build real things, but forgiving enough that you can mess around. The built-in hosting is a nice bonus.

For Real Work: Cline

If you're a professional developer who needs to build production software, Cline is the only choice. It respects your existing code, asks before making changes, and produces the highest quality output. The cost is higher, but the quality justifies it.

My Personal Winner

Cline, without hesitation.

Here's why: I'm a professional developer. I need tools that respect my workflow, not tools that try to replace me. Cline treats me like a partner, not a user. It suggests, I approve. It builds, I review. The other two tools treat you like a passenger - you're along for the ride, but you're not driving.

The day after I finished my tests, I had to fix a bug in a production app. I opened Cline, described the bug, and within 5 minutes it had identified the issue and suggested a fix. I approved the change, ran the tests, and deployed. That's the kind of tool I need.

But here's the honest truth: If you're not a developer, Cline will be overwhelming. The API key setup, the approval system, the lack of built-in hosting - it's not beginner-friendly. For you, Replit Agent is probably the better choice.

And if you just want to build a landing page for your startup idea and see if anyone signs up, Bolt.new will get you there in 15 minutes.

Each tool has its place. I'll be keeping all three in my toolbox, but Cline is the one I open every day.

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One last thing: The AI landscape is moving fast. By the time you read this, all three tools will have improved. But the fundamental differences I've described - Bolt.new's simplicity, Replit Agent's balance, Cline's power and control - are baked into their design. Choose based on what kind of builder you are.