Claude Sonnet 4.5 - The New Coding King? (Sonnet 4.5 vs. GPT 5 Codex)

Key Concepts:

• Claude Sonnet 4.5: Anthropic's new AI model, positioned as a leader in AI coding.
• GPT5 Codecs: OpenAI's AI model for coding, used for comparison.
• Agentic Tool Use: The ability of an AI model to effectively use tools to accomplish tasks.
• Claude Code: Anthropic's platform for AI-assisted coding.
• Codeex: An alternative coding platform, used for comparison.
• PRP (Process Requirement Plan): A structured approach to defining AI coding workflows.
• Stripe Integration: Integrating Stripe payment processing into an existing application.
• RAG (Retrieval-Augmented Generation) Agent: An agent that retrieves information to generate responses.

1. Introduction of Claude Sonnet 4.5

• Anthropic released Claude Sonnet 4.5, an AI model for coding.
• Benchmarks indicate that Sonnet 4.5 outperforms previous Anthropic models like Opus 4.1 and potentially surpasses GPT5 Codecs from OpenAI.
• The video aims to test Sonnet 4.5 in practice by building a Stripe integration into an existing application and comparing it to GPT5 Codecs.
• Sonnet 4.5 shows significant improvements in agentic tool use, with a nearly 20% increase in computer use compared to Opus 4.1.
• Anthropic has released Claude Code version 2.0, powered by Sonnet 4.5, with options to switch back to Opus 4.1.
• Improvements include a VS Code extension and enhancements to the Claude Agents SDK for building custom agentic experiences.

2. Live Coding Test: Sonnet 4.5 vs. GPT5 Codecs

• A live coding test is conducted to compare Sonnet 4.5 in Claude Code with GPT5 Codecs in Codeex.
• The task involves building a Stripe integration into an existing agentic application, specifically a chat interface with a RAG agent.
• The existing application allows users to purchase tokens to interact with the agent.
• The Stripe integration is chosen because it is complex enough to reveal differences between the models but not too time-consuming.
• The models are given the same requirements document and work on separate versions of the repository.
• The instruction set follows a structured approach (PRP) to load feature requirements, plan the implementation, break it down into tasks, and execute each task.

3. Execution and Performance Comparison

• During execution, Claude Sonnet 4.5 is significantly faster than GPT5 Codecs.
• Codeex struggles with running commands and is slower to read files.
• Sonnet 4.5 completes the Stripe implementation in 15 minutes, while Opus 4.1 took 35 minutes for the same task.
• Codeex takes 1 hour and 20 minutes to complete the implementation.
• Sonnet 4.5 required minor corrections to URLs between the front end and back end.

4. Results and Analysis

• Claude Sonnet 4.5's implementation includes a Stripe checkout page for purchasing tokens.
• The initial implementation with Sonnet 4.5 had a minor issue with the token count not updating immediately.
• Codeex's implementation has a less polished UI but includes a token history feature.
• Codeex's implementation also has issues with the initial token balance and requires a page refresh to update the token count.
• The presenter notes that Codeex exhibited unusual behavior, such as rereading files after editing them.

5. Conclusion

• Claude Sonnet 4.5 is faster and slightly better than GPT5 Codecs in this specific test.
• Codeex is still a solid platform, and its performance is expected to improve.
• Sonnet 4.5 is currently leading in the AI coding race.
• The presenter encourages viewers to like and subscribe for more content on large language models, agent building, and AI coding.