How to Use Claude Sonnet 4.5, Opus 4.5, GPT-5, Gemini 3 for FREE

Want to harness the power of Claude Sonnet 4.5, GPT-5, Gemini 3, or Opus 4.5 without spending a fortune? You’re in the right place. In this comprehensive guide, I’ll reveal five legitimate methods to access these advanced AI models completely free. These are the exact tools I use daily for coding, automation, and content creation.

Why Use Claude Sonnet 4.5, GPT-5, and Gemini 3?

Before diving into the free methods, let’s understand why these models are worth your attention:

The challenge? Premium pricing can be prohibitive. Claude Sonnet 4.5 costs $3-15 per million tokens, while GPT-5 and Gemini 3 have similar premium pricing. That’s where these free alternatives come in.

Method 1: Droid CLI - 20 Million Free Tokens First Month

Droid CLI by Factory AI is my top recommendation for developers who want extensive free access to premium AI models. This command-line tool offers an incredible 20 million tokens first month at no cost.

What is Droid CLI?

Droid CLI is a powerful command-line interface that provides direct access to multiple AI models including Claude Sonnet 4.5, GPT-5, Claude Opus 4.5, and more. It’s designed specifically for developers who prefer working in the terminal or need to integrate AI into their workflows.

Key Features

How to Get Started with Droid CLI

Step 1: Sign Up and Install

# Visit the website and create an account
# https://go.bitdoze.com/droid-cli

# Install the CLI tool (instructions provided after signup)
curl -fsSL https://app.factory.ai/cli | sh

Step 2: Launch and Configure

# Start Droid CLI
droid

# The interface will prompt you to choose your model

Step 3: Select Your Model

When you launch Droid, you’ll see options to choose between:

• Claude Sonnet 4.5
• Claude Opus 4.5
• GPT-5
• Other supported models

Step 4: Enable Reasoning (Optional)

For complex tasks requiring deep thinking, you can enable reasoning mode which allows the model to think through problems step-by-step before responding.

Real-World Usage Example

Here’s how I use Droid CLI in my daily workflow:

# Launch Droid
droid

# Select Claude Sonnet 4.5 or Opus 4.5
# Enable reasoning mode for complex tasks

# Example prompt
"Create a Python web scraper that extracts product prices from e-commerce sites,
handles pagination, and exports data to CSV with error handling"

The model will process your request and provide comprehensive code with explanations. Each interaction consumes tokens from your 20 million first month allowance.

Monitoring Your Usage

Best Use Cases for Droid CLI

• Backend Development: API creation, database design, server configuration
• Automation Scripts: Task automation, data processing, workflow optimization
• Code Review: Analyzing and improving existing codebases
• Learning: Exploring new programming concepts and frameworks
• Prototyping: Rapid development of proof-of-concept applications

Get 20M Free Tokens with Droid CLI

Method 2: Windsurf IDE - 25 Free Prompts Monthly

Windsurf is a powerful AI-integrated development environment that offers 25 free prompts per month with access to premium models including Claude Sonnet 4.5 and GPT-5.

What Makes Windsurf Special?

Windsurf is more than just an IDE—it’s a complete development environment with AI deeply integrated into every aspect of your workflow. Unlike traditional IDEs with AI plugins, Windsurf is built from the ground up with AI assistance as a core feature.

Key Features

Understanding the Credit System

Windsurf uses a credit-based system where different models have different costs:

Model	Credits per Prompt	Best For
Supernova	Free (unlimited)	General coding, quick questions
Claude Sonnet 4.5	1 credit	Complex coding, reasoning tasks
GPT-5	1 credit	Advanced reasoning, content creation
GPT-4o	0.5 credits	Cost-effective premium performance

With 25 free credits monthly, you can strategically use premium models for complex tasks while leveraging Supernova for routine work.

How to Get Started with Windsurf

Step 1: Download and Install

Visit Windsurf and download the IDE for your operating system (Windows, macOS, or Linux).

Step 2: Create Your Account

Sign up for a free account to access your monthly credit allowance.

Step 3: Choose Your Mode

Windsurf offers two primary interaction modes:

• Chat Mode: Ask questions, get explanations, discuss architecture
• Code Mode: Direct file editing and project-wide changes

Step 4: Select Your Model

Open the model selector and choose based on your needs:

• Use Supernova for general tasks (free, unlimited)
• Reserve Claude Sonnet 4.5 or GPT-5 for complex problems (1 credit each)

Practical Example: Building a Snake Game

Here’s a real-world example of using Windsurf:

Prompt: "Build a snake game in Python with pygame"

The AI will:
1. Plan the project structure
2. Create necessary files
3. Implement game logic
4. Add controls and scoring
5. Provide instructions for running the game

Windsurf’s Cascade feature allows the AI to plan multi-step projects and execute them systematically, creating multiple files and organizing your project structure automatically.

Monitoring Your Usage

Best Use Cases for Windsurf

• Full-Stack Development: Complete web applications with frontend and backend
• Code Refactoring: Improving existing codebases with AI assistance
• Learning New Frameworks: Exploring React, Vue, Angular, etc.
• UI/UX Development: Creating beautiful, responsive interfaces
• Documentation: Generating comprehensive project documentation

Get 25 Free Prompts with Windsurf

Method 3: AgentRouter - $200 Free API Credits

AgentRouter is a newer service that offers an impressive $200 in free API credits to test premium models including GPT-5, Claude Sonnet 4.5, and GLM-4.5.

What is AgentRouter?

AgentRouter is an API routing service that provides access to multiple AI models through a unified interface. While it’s a newer service, the generous $200 free credit makes it worth exploring for testing and development.

Key Features

Available Models

Model	Use Case
GPT-5	Advanced reasoning, content creation
Claude Sonnet 4.5	Complex coding, long-context tasks
GLM-4.5	Agentic tasks, tool integration

How to Get Started with AgentRouter

Step 1: Sign Up

Visit AgentRouter and create an account. You’ll immediately receive $200 in free credits.

Step 2: Create an API Key

1. Navigate to the API Keys section in your dashboard
2. Click “Create New Key”
3. Set a name (e.g., “Development Key”)
4. Choose default grouping
5. Set a quota (e.g., $10 per key for safety)
6. Optionally restrict to specific models
7. Click Submit to generate your key

Step 3: Configure Your IDE

AgentRouter works with multiple development tools. Here’s how to set it up:

For Roo Code (VS Code Extension)

// Create a new profile in Roo Code settings
{
  "profile_name": "AgentRouter Free",
  "provider": "OpenAI Compatible",
  "base_url": "https://agentrouter.org/v1",
  "api_key": "your_api_key_here",
  "model": "gpt-5",
  "enable_streaming": true
}

For Kilo Code

1. Open Kilo Code settings
2. Select “Use my own key”
3. Choose “OpenAI Compatible” provider
4. Enter base URL: https://agentrouter.org/v1
5. Paste your API key
6. Select your preferred model

Important Considerations

Best Use Cases for AgentRouter

• API Development: Building applications that use AI models
• Batch Processing: Processing large amounts of data
• Experimentation: Testing different models and approaches
• Cost Comparison: Evaluating which model works best for your needs

Get $200 Free Credits with AgentRouter

Method 4: Google Antigravity IDE - Free Gemini 3 Pro Access

Google Antigravity is Google’s new agentic development platform that’s available in public preview at no charge with generous rate limits on Gemini 3 Pro usage. It also includes access to Claude Sonnet 4.5, Claude Opus 4.5, and GPT-OSS models.

What is Google Antigravity?

Google Antigravity is more than just an AI-powered IDE—it’s an agent-first platform designed for a future where AI agents can autonomously plan and execute complex, end-to-end software tasks. While the core provides a familiar IDE experience, Antigravity evolves the concept with browser control capabilities, asynchronous interaction patterns, and multi-agent orchestration.

Key Features

Core Tenets of Antigravity

Google built Antigravity around four key principles:

Tenet	Description
Trust	Task-level abstractions with artifacts and verification results for user validation
Autonomy	Agents operate across code editor, terminal, and browser simultaneously
Feedback	Async feedback through Google-doc-style comments on text and visual artifacts
Self-improvement	Knowledge management allows agents to learn from past work

How Antigravity Works

Editor View (Synchronous):

• State-of-the-art AI-powered IDE experience
• Tab completions and inline commands
• Fully functioning agent in the side panel
• Perfect for focused, hands-on development

Manager View (Asynchronous):

• Mission control for spawning multiple agents
• Orchestrate agents across multiple workspaces in parallel
• Inbox notifications for agent progress
• Ideal for running background research while focusing on other tasks

Artifacts and Verification

Unlike tools that show every single tool call or only the final code change, Antigravity provides context at a natural task-level abstraction through Artifacts:

How to Get Started with Antigravity

Step 1: Visit the Platform

Go to antigravity.google and sign up for the public preview.

Step 2: Download and Install

Download the Antigravity IDE for your operating system (macOS, Linux, or Windows).

Step 3: Choose Your Model

Select from available models:

• Gemini 3 Pro - Google’s most intelligent model (generous free limits)
• Claude Sonnet 4.5 - Anthropic’s top coding model
• Claude Opus 4.5 - Anthropic’s most powerful model for complex reasoning
• GPT-OSS - OpenAI’s model offering

Step 4: Start Building

Use either the Editor view for hands-on coding or the Manager view to spawn autonomous agents for complex tasks.

Real-World Use Case Example

Here’s how Antigravity’s autonomous capabilities work:

Task: "Build a new frontend feature and verify it works"

The Antigravity Agent will:
1. Write code for the new frontend feature
2. Use the terminal to launch localhost
3. Actuate the browser to test the feature works
4. Provide screenshots and recordings as verification
5. All without manual intervention

Best Use Cases for Antigravity

• Full-Stack Development: Leverage browser control for end-to-end testing
• Complex Multi-File Projects: Let agents plan and execute across your codebase
• Parallel Development: Run multiple agents on different tasks simultaneously
• Automated Testing: Agents verify their own work through browser automation
• Research Tasks: Spawn background agents for research while you focus elsewhere

Try Google Antigravity Free

Method 5: GitHub Copilot - 30-Day Free Trial + Free Tier

GitHub Copilot offers a 30-day free trial of their Pro plan, plus an ongoing free tier. This gives you access to GPT-5 mini (unlimited), Claude Sonnet 4.5, Claude Opus 4.5, and other premium models through a polished, production-ready platform.

What is GitHub Copilot?

GitHub Copilot is the most mature AI coding assistant available, deeply integrated with GitHub’s ecosystem. It offers code completion, chat assistance, CLI tools, and autonomous coding agents—all in one subscription that starts with a generous free trial.

Free Access Options

Plan	What You Get
30-Day Free Trial	Full Pro features, no credit card required
Free Tier	50 premium requests/month ongoing
Pro ($10/month)	Unlimited GPT-5 mini + 300 premium requests

Key Features

Available Models in GitHub Copilot

Model	Premium Requests	Best For
GPT-5 mini	Unlimited (Pro)	Daily coding tasks
Claude Sonnet 4.5	1×	Complex algorithms, architecture
Claude Opus 4.5	3×	Most complex reasoning tasks
GPT-5	1×	Advanced reasoning
Gemini 2.0 Flash	0.25×	Quick questions (efficient!)
Claude Haiku 4.5	0.33×	Fast responses

How to Get Started with GitHub Copilot

Step 1: Sign Up for Free Trial

Visit GitHub Copilot Plans and start your 30-day free trial. No credit card required.

Step 2: Install in Your IDE

# For Zed (recommended for speed)
brew install zed
# Enable Copilot in Settings → Extensions

# For VS Code
# Extensions → Search "GitHub Copilot" → Install

Step 3: Install CLI (Optional)

# Install GitHub CLI
brew install gh

# Install Copilot CLI extension
gh extension install github/gh-copilot

# Use it
copilot -p "Create a Next.js app with auth"

Step 4: Enable Latest Models

Visit https://github.com/settings/copilot/features and enable:

• Model choice
• Preview features
• Latest models

Copilot Features Overview

Best Use Cases for GitHub Copilot

• Daily Development: Unlimited GPT-5 mini handles 90% of coding tasks
• Complex Problems: Switch to Claude Sonnet 4.5 or Opus 4.5 for architecture decisions
• Terminal Workflows: Use CLI for DevOps and automation
• Team Collaboration: Deep GitHub integration for PRs and issues
• Learning: Great for exploring new languages and frameworks

Start 30-Day Free Trial - GitHub Copilot

Comparison: Which Free Method is Best?

Here’s a comprehensive comparison to help you choose the right option:

Feature	Droid CLI	Windsurf	AgentRouter	Antigravity	GitHub Copilot
Free Allowance	20M tokens	25 prompts/month	$200 credits	Generous limits	30-day trial + 50/month
Models	Claude 4.5, Opus 4.5, GPT-5	Claude 4.5, GPT-5, Supernova	GPT-5, Claude 4.5, GLM-4.5	Gemini 3, Claude 4.5, Opus 4.5, GPT-OSS	Claude 4.5, Opus 4.5, GPT-5
Best For	CLI users, automation	IDE development	API integration	Agentic workflows	Professional dev
Reliability	High	High	Moderate	High	Very High
Learning Curve	Medium	Low	Medium	Medium	Low
IDE Integration	Yes	Built-in	Yes (multiple)	Built-in	Multi-IDE
Browser Control	No	No	No	Yes	No
Renewal	First Month	Monthly	One-time	Ongoing preview	Monthly

My Recommendations

Choose Droid CLI if you:

• Prefer working in the terminal
• Need extensive token allowance
• Want access to Claude Opus 4.5 for complex tasks
• Focus on backend development and automation

Choose Windsurf if you:

• Want a complete IDE experience
• Prefer visual development tools
• Need both chat and code modes
• Work on full-stack projects

Choose AgentRouter if you:

• Need API access for custom applications
• Want to test multiple models extensively
• Are building integrations
• Don’t mind occasional reliability issues

Choose Google Antigravity if you:

• Want autonomous agents that control browser for testing
• Need to run multiple agents in parallel
• Prefer an agent-first development approach
• Want access to Gemini 3 Pro and Claude Opus 4.5

Choose GitHub Copilot if you:

• Want the most polished, production-ready experience
• Use multiple IDEs and need consistent experience
• Value deep GitHub integration
• Need CLI tools for DevOps workflows
• Want access to Claude Opus 4.5 for complex reasoning

Conclusion

Access to Claude Sonnet 4.5, GPT-5, Gemini 3, and Opus 4.5 doesn’t have to break the bank. With these five free methods, you can:

✅ Get 20 million tokens monthly with Droid CLI for extensive development work

✅ Use 25 premium prompts in Windsurf’s powerful IDE environment

✅ Experiment with $200 in credits through AgentRouter’s API

✅ Access Gemini 3 Pro and Opus 4.5 free with Google Antigravity’s agent-first platform

✅ Try GitHub Copilot free for 30 days plus ongoing free tier access

Start with all five services to maximize your free access and find which works best for your workflow. Whether you’re learning to code, building side projects, or exploring AI capabilities, these tools provide everything you need to get started without spending a cent.

Get 20M Free Tokens - Droid CLI Get 25 Free Prompts - Windsurf Get $200 Credits - AgentRouter Try Antigravity Free - Gemini 3 GitHub Copilot - 30 Day Trial

Remember to use these resources wisely, monitor your usage, and take advantage of all five platforms to maximize your free access to the world’s most powerful AI models. Happy coding!