Antigravity vs Bolt.new vs Replit Agent: Which AI App Builder Wins in 2025?
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Nick
December 27, 2025
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Antigravity vs Bolt.new vs Replit Agent: Which AI App Builder Wins in 2025?
The AI App Builder Showdown: 3 Tools, 3 Approaches, 1 Winner?
The AI coding landscape has exploded in 2025. Three tools dominate developer discussions: Google Antigravity (the IDE powerhouse), Bolt.new (the instant app generator), and Replit Agent (the autonomous coding companion). Each promises to revolutionize how we build software—but they take fundamentally different approaches.
I spent 3 weeks building identical projects with all three tools: a task management SaaS app with authentication, database, payments, and deployment. This comparison shares real findings from actual development work, not marketing fluff.
TL;DR: Antigravity wins for professional developers, Bolt.new wins for rapid prototyping, Replit Agent wins for beginners. Keep reading for the deep dive.
Google Antigravity is Google's flagship AI-powered IDE, launched in late 2024 and rapidly evolving through 2025. Built on the Gemini 3 model with an industry-leading 1 million token context window, it represents the "professional developer" approach to AI coding.
Philosophy: AI as a pair programmer that enhances your skills
Key Features:
1 million token context window (can understand entire codebases)
Agent Mode for autonomous multi-file tasks
MCP (Model Context Protocol) servers for external integrations
Deep VS Code extension integration
.antigravity rules files for project-specific AI behavior
Native Google Cloud integration
Best For: Professional developers, large projects, teams, production applications
What is Bolt.new?
Bolt.new (by StackBlitz) burst onto the scene as the "instant app generator." Type a description, and within seconds you have a working web application in your browser. It's powered by Claude 3.5 Sonnet and focuses on speed over customization.
Philosophy: AI that builds entire apps from prompts instantly
Key Features:
Instant app generation from natural language
In-browser development environment (WebContainers)
One-click deployment
Real-time preview as you iterate
Support for React, Vue, Svelte, and more
Built-in package management
Best For: Rapid prototyping, demos, MVPs, non-developers, hackathons
What is Replit Agent?
Replit Agent is an autonomous AI coding assistant built into Replit's cloud IDE. Unlike chatbots, it can independently plan, write, debug, and deploy code with minimal human intervention. Think of it as a junior developer that never sleeps.
Philosophy: AI that autonomously builds what you describe
Key Features:
Autonomous task execution (plans and implements)
Multi-file editing without manual intervention
Automatic debugging and error fixing
Built-in deployment to Replit hosting
Conversation-based iteration
Access to Replit's ecosystem (databases, secrets, etc.)
Best For: Beginners, learning to code, small projects, quick experiments
Deep Dive: Testing Methodology
To fairly compare these tools, I built the same application three times:
The Project: TaskFlow SaaS
User authentication (email + OAuth)
Task CRUD operations with categories
Team collaboration features
Stripe subscription payments
Dashboard with analytics
Production deployment
Evaluation Criteria:
Time to first working version
Code quality and maintainability
Ease of customization
Debugging experience
Final production readiness
Let's see how each tool performed.
Round 1: Getting Started (Speed to First App)
Bolt.new: 47 Seconds
I typed: "Create a task management app with user authentication, task lists, and a clean modern UI"
Within 47 seconds, I had:
A fully functional React app
Mock authentication system
Beautiful UI with Tailwind CSS
Local storage persistence
Responsive design
The instant gratification is incredible. However, this was a prototype—not production code.
Replit Agent: 4 Minutes
I described the same requirements. Replit Agent:
Created a project plan (30 seconds)
Asked clarifying questions about tech stack
Built the application file by file
Set up a basic SQLite database
Created working authentication
More thorough than Bolt.new, but slower. The code was functional but needed refinement.
Antigravity: 12 Minutes
With Antigravity, I took a more structured approach:
Created project with Next.js 15 template
Set up .antigravity rules file for my preferences
Used Agent Mode: "Set up authentication with Supabase, create task model, build dashboard layout"
Reviewed and approved each file change
Slowest to start, but the code was production-ready from the beginning. Proper TypeScript types, error handling, and best practices baked in.
Functional, but missing input validation, error handling, and proper HTTP status codes. About 70% of the way to production-ready.
Round 2 Winner: Antigravity (by a wide margin)
Round 3: Customization & Iteration
Antigravity: Full Control
When I wanted to add a Kanban board view:
Described the feature in chat
Agent Mode proposed file changes
I reviewed each change before applying
Made manual adjustments where needed
Feature integrated seamlessly
The .antigravity rules file meant the AI understood my coding preferences:
# .antigravity rules
- Use Server Components by default
- Prefer Tailwind CSS with custom design tokens
- Always include proper TypeScript types
- Use Zod for validation
- Follow the repository pattern for database access
Every subsequent generation followed these rules. Consistency across the entire codebase.
Bolt.new: Limited After Generation
Customizing Bolt.new apps is challenging:
The in-browser editor is basic
Making structural changes often breaks things
No proper Git history
Exporting to a real IDE requires setup work
I tried adding the Kanban view, but the AI kept fighting my changes. Eventually, I exported to VS Code and finished manually.
Replit Agent: Good But Slow
Replit Agent handled customization well:
Described the Kanban feature
Agent planned the implementation
Made changes across multiple files
Fixed bugs it introduced
Feature worked after 2 iterations
The process took longer than Antigravity because the Agent sometimes went in wrong directions and had to backtrack.
Round 3 Winner: Antigravity
Round 4: Handling Complex Features
I challenged each tool with a complex requirement: "Implement Stripe subscription payments with multiple tiers, usage tracking, and webhook handling."
Antigravity: Nailed It
Agent Mode produced:
Complete Stripe integration with proper webhook signature verification
Subscription model with trial periods
Usage metering with overage calculations
Customer portal integration
Proper error handling and retry logic
The 1M token context window meant it understood my entire codebase and integrated payments seamlessly with existing auth and database patterns.
Bolt.new: Struggled
Bolt.new couldn't handle this complexity:
Generated basic Stripe Checkout (no subscriptions)
No webhook handling
Mock implementations instead of real integration
Required significant manual work to complete
This is where Bolt.new's "instant app" approach breaks down. Complex features need iterative development.
Replit Agent: Partial Success
Replit Agent made progress but got stuck:
Created basic subscription checkout
Webhook handling had security issues
Usage tracking was incomplete
Needed 3 rounds of corrections
The Agent tried hard but lacked the context understanding to implement complex integrations correctly.
Round 4 Winner: Antigravity (decisively)
Round 5: Debugging Experience
Antigravity: Best-in-Class
When I encountered a cryptic error with Server Actions:
Error: Invariant: headers() expects to have requestAsyncStorage
Antigravity:
Identified it was a Next.js 15 issue with cookies in Server Actions
Explained the root cause (calling cookies() outside request context)
Showed three solutions ranked by best practice
Offered to implement the fix
Updated all affected files automatically
Bolt.new: Limited
Debugging in Bolt.new's browser environment is frustrating:
Console errors are hard to trace
No breakpoint debugging
AI sometimes suggests fixes that create new bugs
Complex errors require exporting to a real IDE
Replit Agent: Persistent But Slow
Replit Agent's debugging approach:
Notices the error
Tries a fix automatically
If that fails, tries another approach
Eventually finds a solution (or asks for help)
It works, but watching the Agent try 5 different approaches isn't efficient.
Round 5 Winner: Antigravity
Round 6: Deployment & Production
Antigravity: Any Platform
Antigravity doesn't lock you into a platform:
Deploy to Vercel, AWS, Railway, Render, or anywhere
Standard build outputs work everywhere
Docker support out of the box
CI/CD integration with any provider
I deployed my TaskFlow app to Vercel in under 2 minutes with full preview environments.
Bolt.new: Built-in Deployment
Bolt.new has one-click deployment:
Click "Deploy" and it's live
Custom domains supported
Automatic HTTPS
However, you're locked into their infrastructure. Need to move to AWS later? You'll need to export and reconfigure everything.
Replit Agent: Replit Hosting
Replit deployment is simple:
Click "Deploy" → Live on Replit's servers
Custom domains with paid plans
Built-in secrets management
Like Bolt.new, you're locked into their ecosystem. Production workloads may face scaling limitations.
Yes! A common workflow: prototype in Bolt.new, then export to Antigravity for production development. Or learn with Replit Agent, then graduate to Antigravity for professional work.
Which is best for complete beginners?
Bolt.new if you just want an app. Replit Agent if you want to learn coding while building.
Which handles large codebases best?
Antigravity, by far. Its 1M token context window can understand projects that would overwhelm the others.
What about GitHub Copilot?
Copilot ($10/month) is a great autocomplete tool but can't do what these three do. It's best as a complement to Antigravity, not a replacement.
Can Bolt.new handle databases?
Bolt.new currently focuses on frontend. For backend and databases, you'll need Antigravity or Replit Agent.
Is my code private with these tools?
Antigravity: Yes, with enterprise plans. Bolt.new: Code is stored on their servers. Replit: Yes, with paid plans.
Conclusion
After building the same app three times, my verdict is clear:
Google Antigravity is the best overall tool for serious developers. The code quality, customization, and context understanding are unmatched. Yes, it takes longer to learn, but the investment pays massive dividends.
Bolt.new is magical for prototyping. Nothing else creates working apps as fast. Just don't expect to take that code to production without significant rework.
Replit Agent is the best learning companion. If you're new to coding or want an AI that explains its work, it's an excellent choice for smaller projects.
The best developers in 2025 will use all three—choosing the right tool for each situation.