Claude 4 Comprehensive Guide: The World’s Best Coding AI Opens a New Era of Development

The Birth of the World’s Best Coding AI

On May 22, 2025, Anthropic delivered a new shock to the AI industry. The company’s announcement of Claude 4 achieved an astonishing 72.5% score on the software engineering benchmark SWE-bench, establishing its position as the world’s best coding AI model¹. This figure significantly exceeded OpenAI’s GPT-4 and Google’s Gemini series.

Claude 4 goes beyond mere performance improvements, featuring innovative capabilities that change the very concept of AI development. Particularly noteworthy is its ability to continue coding autonomously for up to 7 hours on complex open-source projects. This demonstrates that AI has begun functioning as a true partner rather than merely an assistant tool for developers.

Hybrid Reasoning: A Revolution in Thought Processes

One of Claude 4’s most innovative features is “hybrid reasoning”². This system allows switching between two modes: immediate response mode and deep thinking mode.

In immediate response mode, it provides quick responses similar to traditional AI. Meanwhile, in deep thinking mode, the AI takes time to consider problems, deliberating on possible solutions before responding. This thinking process is displayed in a user-friendly summary format, allowing users to understand how the AI reached its conclusions.

Furthermore, when using parallel test-time compute (generating multiple solutions and selecting the best), SWE-bench scores reached 79.4% for Opus 4 and 80.2% for Sonnet 4. This suggests that AI is beginning to possess true problem-solving capabilities rather than simply reproducing memorized patterns.

Opus 4 and Sonnet 4: Two Models for Different Purposes

The Claude 4 family consists of two models designed to meet different needs³.

Claude Opus 4 is Anthropic’s most powerful model. It achieved a 43.2% score on Terminal-bench and excels in complex multi-step tasks. It’s ideal for advanced intellectual work such as refactoring large codebases, gathering information from scattered documents, and long-term digital collaboration.

Claude Sonnet 4 is a model that prioritizes the balance between high performance and cost efficiency. It recorded a slightly higher score than Opus 4 at 72.7% on SWE-bench and excels in everyday coding tasks, code reviews, bug fixes, and customer support agent applications.

In terms of pricing, Opus 4 costs $15 for input and $75 for output per million tokens, while Sonnet 4 is more affordable at $3 for input and $15 for output⁴.

Performance and Evaluation in Development Environments

Following Claude 4’s release, development teams have expressed amazement. GitHub announced the adoption of Claude Sonnet 4 in their new coding agent, GitHub Copilot. According to the company, “Sonnet 4 is achieving breakthrough results in agent scenarios”⁵.

Evaluations in actual development tasks have been impressive. In 16x Eval tests, Opus 4 scored 9.5/10 and Sonnet 4 scored 9.25/10 in a Next.js TODO app creation task. In TypeScript type narrowing problems, Opus 4 scored 8.5/10 and demonstrated deep understanding by presenting two different solutions.

Cursor evaluates Opus 4 as “cutting-edge in coding and a breakthrough in complex codebase understanding.” However, some developers have noted that it “sometimes executes actions beyond what was instructed in the prompt,” highlighting the need for more precise control.

Full Support for the Japanese Market

Claude 4 fully supports Japanese, making it an extremely user-friendly AI for Japanese developers and business users. Advanced Japanese processing enables natural Japanese dialogue, document summarization, and code generation.

Getting started in Japan is simple - just sign up on the official website with an email address or Google account. Mobile apps are available for both iOS and Android, and users can begin after SMS authentication.

For pricing plans, the free version provides access to Claude Sonnet 4, while upgrading to the Claude Pro plan at approximately 3,400 yen ($20) per month grants access to the top-tier Opus 4 model.

In business applications, Slack integration enables various business support uses including internal FAQ chatbots, meeting minutes creation, and document summarization. Particularly, automatic generation of programming code in languages like Python completes quickly, contributing to productivity improvements with high-precision coding.

API and Enterprise Support

For developers, Claude 4 is available through Anthropic API, Amazon Bedrock, and Google Cloud Vertex AI. Newly added API features include:

Code Execution Tool: Real-time execution and verification of generated code
MCP Connector: Integration with external data sources via Model Context Protocol
Files API: Direct file processing and manipulation
Prompt Caching: Up to 1 hour of caching enabling 90% cost reduction

For enterprise users, Claude Code has begun general availability. It provides a seamless pair programming environment through background task execution via GitHub Actions and native integration with VS Code and JetBrains.

Commitment to Safety

Anthropic has also focused on safety evaluation for Claude 4. In the company’s 4-level safety scale, Opus 4 is classified as “Level 3”. This means the model carries “significantly high risk” due to its extreme power. Meanwhile, Sonnet 4 is classified as “Level 2”.

Both models underwent rigorous testing including misuse scenarios, adversarial vulnerabilities, and third-party evaluations before release. This ensures an environment where AI can be utilized responsibly despite its powerful capabilities.

Claude 4 is not merely a tool but holds the potential to transform the development process itself. In this new era, developers will be able to focus on more creative and valuable work through collaboration with AI.