Claude Opus 4 Guide - What's New and How to Use It for Coding

Claude Opus 4 represents a significant leap in AI capabilities. For developers, this means more powerful code generation, better reasoning, and deeper understanding of complex codebases.

Here's everything you need to know about Opus 4 and how to leverage it effectively.

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Table of Contents

1. What's New in Opus 4
2. Capabilities for Developers
3. When to Use Opus 4
4. Best Practices
5. Pricing & Access
6. Comparison to Other Models

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What's New in Opus 4

Enhanced Reasoning

Opus 4 shows significantly improved:

• Multi-step problem solving
• Logical deduction
• Planning and strategy
• Understanding complex requirements

For coding, this means:

• Better architecture decisions
• More thorough edge case handling
• Improved debugging of complex issues
• Better understanding of trade-offs

Extended Thinking

Opus 4 can "think" longer before responding:

• More careful analysis
• Fewer logical errors
• Better handling of ambiguity
• More coherent long-form outputs

Improved Instruction Following

The model better understands:

• Complex multi-part instructions
• Nuanced requirements
• Implicit constraints
• Context from earlier in conversation

Agentic Capabilities

Enhanced for autonomous tasks:

• Better tool use
• More reliable multi-step execution
• Improved error recovery
• Better state management

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Capabilities for Developers

Code Generation

What's improved:

• More complete implementations
• Better handling of complex logic
• Improved awareness of edge cases
• More idiomatic code per language

Example prompt:

Create a rate limiter middleware for Express.js that:
- Uses sliding window algorithm
- Stores state in Redis
- Supports different limits per route
- Has graceful degradation if Redis is down
- Returns proper HTTP 429 responses

Include TypeScript types and comprehensive error handling.

Opus 4 will produce production-ready code with all edge cases handled.

Code Review

What's improved:

• Catches more subtle bugs
• Better security awareness
• More nuanced suggestions
• Understands context better

Example:

Review this authentication code for security issues,
paying special attention to:
- Session management
- Token validation
- Timing attacks
- Edge cases that could bypass auth

[paste code]

Debugging Complex Issues

What's improved:

• Better at forming hypotheses
• More systematic debugging approach
• Can reason about async/concurrent issues
• Better memory of conversation context

Example:

I have a race condition that only appears under load.

The system: [describe architecture]
The symptom: [describe behavior]
What I've observed: [observations]

Help me:
1. Form hypotheses about the root cause
2. Design tests to confirm/eliminate each
3. Suggest fixes for the most likely cause

Architecture & Design

What's improved:

• More nuanced trade-off analysis
• Better understanding of scale implications
• Improved system design reasoning
• More practical recommendations

Example:

I'm designing a notification system for a mobile app.

Requirements:
- Support push, email, SMS
- User preferences per channel
- Batch notifications to prevent spam
- Analytics on engagement
- Scale to 10M users

Please:
1. Propose a high-level architecture
2. Discuss key design decisions
3. Identify potential bottlenecks
4. Suggest tech stack

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When to Use Opus 4

Best Use Cases

1. Complex architecture decisions When you need to think through system design with many considerations.

2. Debugging mysterious issues Race conditions, memory leaks, intermittent failures—problems requiring deep analysis.

3. Major refactoring When you're restructuring significant portions of code and need to maintain correctness.

4. Security-critical code Authentication, authorization, crypto—areas where subtle bugs have big consequences.

5. Learning complex topics When you need nuanced explanations with depth.

When to Use Sonnet Instead

Opus 4 is overkill for:

• Simple code generation
• Routine debugging
• Standard CRUD operations
• Quick questions
• High-volume tasks

Sonnet is faster and cheaper for these.

Decision Matrix

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Best Practices

Practice 1: Invest in Context

Opus 4 uses context better than previous models. Provide:

Context about the system:
[architecture overview]

Context about this feature:
[what it does, why it exists]

Context about constraints:
[performance requirements, compatibility needs]

Now, [your actual question]

Practice 2: Ask for Reasoning

Get more value by requesting explanations:

For this design decision:
1. Propose options
2. For each option, explain:
   - Advantages
   - Disadvantages
   - When it's the right choice
3. Give your recommendation with reasoning

Practice 3: Multi-Turn Refinement

Use Opus for deep dives:

Turn 1: "Here's my system. What potential issues do you see?"
Turn 2: "Let's dig into issue #2. What's the root cause?"
Turn 3: "How would you fix it without breaking X?"
Turn 4: "Show me the implementation"
Turn 5: "Review for edge cases"

Practice 4: Extended Thinking

For complex problems, explicitly request thinking:

This is a complex problem. Before answering:
1. Identify all the considerations
2. Think through different approaches
3. Consider potential issues with each
4. Then provide your recommendation

Take your time—I'd rather have a thorough answer 
than a quick one.

Practice 5: Tool Use Setup

When using Opus with tools (API):

# Give Opus clear tool descriptions
tools = [
    {
        "name": "read_file",
        "description": "Read contents of a file. Use when you need to see code.",
        "parameters": {
            "filepath": "Path to the file to read"
        }
    },
    {
        "name": "run_command",
        "description": "Execute a shell command. Use for testing or builds.",
        "parameters": {
            "command": "The command to run"
        }
    }
]

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Pricing & Access

API Pricing

Opus is 5x more expensive than Sonnet.

Cost Optimization

Strategies:

1. Use Opus only when needed
2. Start with Sonnet, escalate to Opus
3. Batch complex questions together
4. Use shorter prompts for simple tasks

Typical monthly costs:

• Light use (hobby): $10-30
• Heavy use (professional): $50-200
• Team use: $200-1000

Access Options

Claude.ai Pro ($20/mo):

• Access to Opus 4
• Limited usage
• Good for exploration

Claude.ai Team ($30/user/mo):

• More Opus usage
• Team features
• Better for companies

API:

• Pay per token
• Full control
• Best for integration

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Comparison to Other Models

Opus 4 vs Sonnet 3.5

Use Sonnet for 80% of tasks, Opus for the hard 20%.

Opus 4 vs GPT-4 Turbo

Opus for precision, GPT-4 for speed.

Opus 4 vs GPT-o1

o1 for math/logic puzzles, Opus for practical development.

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Getting Started

Step 1: Get Access

Options:

1. Claude.ai Pro subscription
2. API access via Anthropic
3. Cursor with Opus enabled

Step 2: Start with a Hard Problem

Don't waste Opus on easy tasks. Try:

• That bug you've been stuck on
• Architecture decision you're uncertain about
• Code review for critical code

Step 3: Compare to Sonnet

Same prompt, both models. Notice:

• Depth of reasoning
• Edge case awareness
• Quality of explanation

Step 4: Develop Your Workflow

Figure out your personal triggers for Opus:

• Spent 30+ minutes debugging? Opus time.
• Major architecture decision? Opus time.
• Routine feature? Sonnet's fine.

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Tips for Specific Tasks

For Architecture

I need to design [system].

Requirements:
[list requirements]

Constraints:
[list constraints]

Please:
1. Propose 2-3 architectural approaches
2. Analyze trade-offs deeply
3. Recommend one with reasoning
4. Identify risks in that approach
5. Suggest mitigations

For Complex Debugging

I've been stuck on this bug for [time].

The system:
[describe relevant parts]

The bug:
[describe symptoms precisely]

What I've tried:
[list attempts]

My current hypothesis:
[what you think might be wrong]

Please help me:
1. Evaluate my hypothesis
2. Suggest other possibilities
3. Design a debugging approach
4. Predict what we'll find

For Security Review

Review this code for security:

Context: [what it does, threat model]

[paste code]

Check for:
- OWASP Top 10 vulnerabilities
- Logic errors that bypass security
- Timing attacks
- Input validation gaps
- Privilege escalation
- Information disclosure

Rate severity of each finding.

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Conclusion

Claude Opus 4 is a significant upgrade in AI capabilities for developers. The key is knowing when to use it:

Use Opus 4 for:

• Complex reasoning required
• High-stakes code
• Deep analysis
• Architecture decisions

Use Sonnet for:

• Day-to-day coding
• Quick tasks
• Volume work
• Budget optimization

Master the art of model selection, and you'll get the best of both: Sonnet's speed for most work, Opus's depth when it matters.

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