How to Set Up Claude Code with Opus 5 in 5 Minutes (The Free Upgrade That Doubles Your Output)

Anthropic's Claude Opus 5, shipped July 24, is now available at the same $5/$25 per million tokens as Opus 4.8, offering improved performance and background agent support. Users can switch to Opus 5 via the Claude Code CLI by running `claude --model claude-opus-5` or using the `/model` command, and the update requires Claude Code v2.1.220. The author reports a 30–40% prompt reduction after adding a CLAUDE.md file for project context, and Opus 5 completes multi-feature specs in one prompt versus two on 4.8.

Claude Opus 5 shipped July 24. If you’re still running Claude Code on other cheaper models, you’re leaving performance on the table. Here’s the complete setup, from installing Claude Code to running your first Opus 5 build. Open your terminal and run: npm install -g @anthropic-ai/claude-code Already have it? Update to the latest version: npm update -g @anthropic-ai/claude-code Check your version: claude --version You need v2.1.220 to get all the latest features background agents, notifications, Opus 5 support . Launch Claude Code in any project folder: claude Once inside, switch models: /model claude-opus-5 Or launch directly with Opus 5: claude --model claude-opus-5 That’s it. You’re on Opus 5. It’s the same $5/$25 per million tokens as Opus 4.8. Opus 5 is smarter than 4.8. Give it project context, and it gets even better. Create a CLAUDE.md file in your project root: Project ContextThis is a describe your project built with your stack . Tech Stack- Frontend: React + TypeScript + Tailwind- Backend: Supabase- Deployment: Vercel Coding Conventions- Functional components with hooks- Named exports- Tailwind utility classes for styling- Early returns for guard clauses Important Rules- Never remove existing functionality when adding features- Handle loading and error states on every component- Mobile responsive on every page- No console.log in production code Claude Code reads this file at the start of every session. Your prompts get shorter and your first-pass accuracy goes up. I saw a 30–40% prompt reduction after adding CLAUDE.md to my projects. Test it on something real. Here’s a starter spec you can paste directly: Build a task manager app.Stack: React, Vite, TypeScript, Tailwind CSS.Features:1. Add task form with title and priority dropdown Low, Medium, High 2. Task list with checkboxes to mark complete3. Filter by priority and completion status4. Task count showing total, completed, and remaining5. Local storage persistence - tasks survive page refresh6. Clean modern design, mobile responsiveAlso create Supabase SQL and ensure the UI is impressive This spec tests multi-feature coherence, state management, and local storage… all areas where Opus 5 outperforms 4.8. On Opus 4.8, this spec typically needs 2 prompts filter connection breaks on first pass . On Opus 5, it should complete in 1. As your main build runs, start a second task in the background: claude --background "Write unit tests for all utility functions in this project using Vitest" Your main session keeps running. The background agent writes tests, commits them, and opens a draft PR when done. You get notified. Two tasks running in parallel in the same terminal. The model is better, and thinking is on by default. If safety classifiers trigger, it falls back to 4.8 gracefully instead of blocking your request entirely. You’re now running the strongest Opus model Anthropic has shipped, at the same price you were paying for last month’s version. I write about building solo with AI, one real project at a time. Follow me on Medium to get more content. How to Set Up Claude Code with Opus 5 in 5 Minutes The Free Upgrade That Doubles Your Output https://pub.towardsai.net/how-to-set-up-claude-code-with-opus-5-in-5-minutes-the-free-upgrade-that-doubles-your-output-a8948f3c849c was originally published in Towards AI https://pub.towardsai.net on Medium, where people are continuing the conversation by highlighting and responding to this story.