How to Use Copilot Claude Sonnet & Opus models for Free Inside Claude Code (After VS Code Copilot Removed Them)

GitHub quietly removed Claude Sonnet 4.5 and Opus 4.5 from the VS Code Copilot extension. But here's what nobody is talking about — they're still fully accessible through the Copilot API. In this guide I'll show you exactly how to get Claude Sonnet 4.5 running inside Claude Code CLI completely free using an open-source proxy. Students pay $0. Everyone else pays $10/month for Copilot — still way cheaper than Anthropic's API. Why This Works GitHub removed the models from the VS Code UI — not from their API. The claude-sonnet-4.5 and claude-opus-4.5 models still respond normally when called directly via api.githubcopilot.com. We exploit this using three tools: OpenCode CLI — authenticates with GitHub and stores your Copilot token claude-code-proxy — translates Anthropic API → OpenAI API format Claude Code CLI — Anthropic's agentic coding tool The Architecture Claude Code CLI │ Anthropic format ▼ claude-code-proxy (localhost:8082) │ OpenAI format ▼ api.githubcopilot.com │ ▼ claude-sonnet-4