Claude Opus 4 and Sonnet 4 Technical Review: The Best Coding Models for Developers?

Yusuf Ishola's headshotYusuf Ishola· May 23, 2025

Anthropic just dropped the fourth version of the Claude models, and it's clear they're meant for developers.

After months of speculation, we finally have two new models: Claude Opus 4 and Claude Sonnet 4—both featuring enhanced hybrid reasoning capabilities, allowing them to switch between instant responses and extended thinking.

Claude Opus 4 and Sonnet 4 Technical Review: The Best Coding Models for Developers

Let's explore the new so-called "Best Coding Models in the World" and see just how well that nickname holds up.

Table Of Contents

What's New in Claude 4?

Claude 4 builds on Anthropic's hybrid reasoning approach, now with significant improvements for developers:

  • Enhanced tool calling: Models can use multiple tools in parallel and switch between reasoning and tool use dynamically
  • Extended thinking with tools: Unlike previous reasoning models, Claude 4 can actively use tools while working through problems—creating a feedback loop that dramatically improves problem-solving
  • Autonomous coding sessions: Claude Opus 4 can maintain context and code effectively for up to 7 hours straight
  • Better instruction following: Reduced tendency to over-engineer solutions or add unnecessary features
  • Improved memory capabilities: Better at creating and maintaining memory files for long-term task awareness
  • Claude Code now generally available: Anthropic's command-line AI assistant, is now generally available with VS Code and JetBrains integrations, GitHub PR reviews, and an SDK for building custom coding agents. The tool can handle complex, multi-step development workflows directly from your terminal.

Here's a quick rundown of the key numbers:

FeatureClaude Opus 4Claude Sonnet 4
Context Window200K tokens200K tokens
Pricing$15 input / $75 output per 1M tokens$3 input / $15 output per 1M tokens
Knowledge CutoffMarch 2025March 2025
Safety LevelASL-3ASL-2
Best ForComplex reasoning, long-horizon tasksEveryday coding, faster responses

Monitor Claude 4 Usage Before Costs Spiral 🚨

Claude 4's reasoning capabilities can burn through tokens fast, especially with extended thinking enabled. Track every API call with real-time cost monitoring and set alerts before your development experiments break the bank.

import Anthropic from "@anthropic-ai/sdk";

const anthropic = new Anthropic({
  baseURL: "https://anthropic.helicone.ai",
  apiKey: process.env.ANTHROPIC_API_KEY,
  defaultHeaders: {
    "Helicone-Auth": `Bearer ${process.env.HELICONE_API_KEY}`,
  },
});

Claude 4 Benchmark Performance

Claude 4 Benchmark Performance

Source: Anthropic

Coding: Impressive numbers

Claude 4 dominates coding benchmarks, with Anthropic claiming it's now "the world's best coding model."

On SWE-bench Verified, which tests real-world GitHub issue resolution, the Claude 4 models scored consistently higher than both OpenAI's developer-focused GPT-4.1 and Google's Gemini 2.5 Pro.

Developer Tip 💡

Interestingly, Sonnet 4 often matches or even outperforms Opus 4 on most coding tasks—likely due to Opus overcomplicating solutions. This suggests that for development work, the smaller and cheaper model might be the sweet spot.

Long-Horizon Tasks: Built for Persistence

Both models excel at sustained, multi-step workflows. Rakuten reported a successful 7-hour coding session, with the models maintaining context and making consistent progress without losing track of objectives.

Math and Science: Strong but Not Dominant

While Claude 4 performs well on mathematical reasoning, it doesn't dominate like it does in coding, scoring comparable results to OpenAI o3 and Gemini 2.5 Pro on AIME 2025 (high school math competition) and GPQA Diamond (graduate-level science reasoning).

Claude 4 Real-World Developer Experience

I had early access to what is Claude 4 (I don't know which model) & I have been very impressed.

— Ethan Mollick, Wharton Professor & AI Influencer

Early testing reveals some impressive capabilities, with notable wins against competitors in practical scenarios.

Head-to-Head: Frontend Aesthetics

I'll give 2.5 Pro the pass. [GPT-4.1] I'll give it a five out of 10 there. Claude came out really solid

— Theo from t3.gg

Testing UI generation prompts across models reveals Claude 4's strength in tasteful design:

  • Claude Sonnet 4: Clean layout with subtle blur effects and professional styling
  • Gemini 2.5 Pro: Decent design but overly bright purple elements
  • GPT-4.1: Poor dark mode handling and basic styling

Claude consistently produces more polished, professional-looking interfaces than competitors.

Document Analysis

In a stress test with a 180-page Nvidia annual report, Claude 4 successfully located specific director compensation details buried on page 53—demonstrating strong needle-in-haystack capabilities for large document analysis.

Additionally, from a Google Analytics screenshot, Claude 4 generated a clean, responsive dashboard with accurate data extraction and visualization, mobile-friendly responsive design, and professional styling that matched the original data layout.

Video Game Creation

Claude 4 shined in the creation of various video games, most of which were playable right in the chat interface (via artifacts).

Claude 4 Opus and Sonnet Pricing

Claude 4 isn't cheap, especially compared to models like GPT-4o Mini:

  • Claude Opus 4: $15/$75 per million tokens (5x more expensive than Claude 3.5 Sonnet)
  • Claude Sonnet 4: $3/$15 per million tokens (same as Claude 3.5 Sonnet)

Hidden costs with reasoning: Extended thinking can dramatically increase costs. Tests show reasoning-enabled models can cost 14x more due to thinking tokens, with one evaluation jumping from $109 to $1,485 when thinking was enabled.

For most development work, Claude Sonnet 4 offers the best value. Reserve Opus 4 for complex reasoning tasks where the premium pricing is justified by time savings.

Slash your AI Costs 🚨

With top AI models being able to tackle problems for hours on end, you'll want to keep a close eye on your token usage. Track every request with real-time cost monitoring and save costs with caching and other features.

How to Access Claude 4

Direct Access Options

Claude.ai Web Interface and Apps

  • Free tier: Access to Claude Sonnet 4 with usage limits
  • Pro tier ($20/month): Unlimited access to both models with extended thinking
  • Max tier ($100/month): 5-20x more usage for heavy users

Developer Access

Anthropic API

  • Usage-based pricing: $3/$15 per million tokens (Sonnet 4), $15/$75 (Opus 4)
  • Full access to both models and extended thinking capabilities
  • Batch processing available with 50% discount

Third-Party Integrations

  • GitHub Copilot: Claude Sonnet 4 now default option
  • Cursor and Windsurf: Integrated for coding assistance
  • Vercel and Replit: Available in their AI platforms

Claude Code

  • Install CLI tool
  • VS Code and JetBrains extensions with inline suggestions
  • GitHub integration for PR reviews and CI fixes

Safety Alert: ASL-3 Protections ⚠️

Claude Opus 4 is the first production model requiring ASL-3 security protections due to concerning behaviors in testing—including self-exfiltration attempts, high-agency actions, and proactive whistleblowing. While not seen in real-world usage, developers should be aware these capabilities exist.

Anthropic's Strategic Pivot: Betting on Developer Infrastructure

Claude 4's release signals a major strategic shift—while OpenAI and Google fight for consumer mindshare, Anthropic is doubling down on becoming the AI infrastructure layer for developers.

This pivot should accelerate innovation across better coding models, deeper IDE integrations beyond simple autocomplete, agentic development workflows that handle multi-step tasks autonomously, and specialized developer APIs designed specifically for development use cases.

Bottom Line

Claude 4 marks the next step in Anthropic's evolution to developer-focused AI infrastructure provider. The models deliver impressive coding capabilities and introduce genuinely useful improvements like enhanced tool calling and sustained autonomous performance.

While the premium pricing and context window limitations restrict adoption for some use cases, the developer community seems to be more than impressed so far by the new models.

If Anthropic can maintain its technical lead in coding while building out its developer ecosystem, this strategy could establish it as the preferred AI provider for serious development work.

Frequently Asked Questions

What's the difference between Claude Opus 4 and Claude Sonnet 4?

Claude Opus 4 is the more powerful model designed for complex reasoning and long-horizon tasks, while Claude Sonnet 4 offers excellent performance for everyday development work at a much lower cost. Interestingly, Sonnet 4 often matches Opus 4 on coding tasks.

How does Claude 4's hybrid reasoning work?

Claude 4 can operate in two modes: standard mode for quick responses and extended thinking mode for deep reasoning. Claude 4 can use tools (web search, code execution, etc.) during its reasoning process, creating a feedback loop that improves problem-solving.

Is Claude 4 worth the higher cost compared to other models?

For complex development work and long-horizon tasks, yes. Claude 4 excels at sustained coding sessions and complex reasoning. However, reasoning costs can be significantly higher due to thinking tokens, so monitor usage carefully with observability tools like Helicone.

What is Claude Code and how do I access it?

Claude Code is a command-line AI assistant that integrates directly into your development workflow. It can be accessed after installation to your CLI but is now available as VS Code and JetBrains extensions as well.

Why does Claude Opus 4 require ASL-3 safety protections?

Claude Opus 4 showed concerning emergent behaviors in testing, including attempts at self-exfiltration and proactive actions like contacting authorities when detecting wrongdoing. ASL-3 protections include enhanced monitoring and deployment restrictions to mitigate these risks.

Questions or feedback?

Are the information out of date? Please raise an issue or contact us, we'd love to hear from you!