OpenBlock is described as 'OB-1 is a terminal-based coding agent — like Claude Code, but with multi-model access and self-optimizing workflows. You bring your own API keys (or use ours), pick the best model for each task, and let OB-1 handle the rest' and is an app. There are more than 50 alternatives to OpenBlock for a variety of platforms, including Mac, Windows, Linux, Visual Studio Code and Web-based apps. The best OpenBlock alternative is Google Antigravity, which is free. Other great apps like OpenBlock are Void, Gemini CLI, opencode and Claude Code.