Anthropic has opened its Claude Hardware Interface (Bluetooth API) to developers, enabling an ESP32-S3-based desk companion to connect directly to the Claude desktop app over Bluetooth Low Energy (BLE).To demonstrate this new feature, the company released an open-source reference project called Claude Desktop Buddy. It currently runs on the M5StickC Plus (an ESP32-based board from M5Stack, about $30 on AliExpress and Amazon) and works as a small interactive hardware companion for Claude. Also, during the recent “Build with Claude” event, the company recommended the ESP32-S3-based M5Stack Cardputer as one of the best hardware options for developers who want to build physical devices that interact with AI agents.Designed as a physical companion device for Claude Cowork and Claude Code on macOS and Windows, it stays on your desk and provides real-time updates on the AI agent’s activity. It also lets you respond to permission requests directly using its buttons, so you can approve or deny actions without going back to the desktop app, making interaction with the AI faster and more convenient.The “Buddy” feature started as a hidden Easter egg and April Fools’ joke inside the Claude Code CLI. It was planned for April 1st, 2026, but it got leaked a day early through an accidental npm source map. Developers could summon it with a simple command to display a reactive ASCII character whose energy and mood changed based on their coding activity. The goal was to make long terminal coding sessions more fun and less boring. But over time, as it got popular, Anthropic decided to expand the concept beyond software. By late April 2026, the company open-sourced the Claude Desktop Buddy project and released a local Bluetooth Low Energy (BLE) API for its desktop apps. You’ll find the code and documentation on GitHub.This hardware interface solves a key problem of frequent user approvals that similar AI systems like StackChan, Loona Deskmate, and Espressif’s EchoEar voice chatbot do not address. Instead of constantly switching back to your computer screen, you can now receive prompts and approve or deny actions directly on the ESP32 device using physical buttons over BLE. The interaction stays local, fast, and private, and no API keys or internet connection are needed. The firmware also keeps the fun “desk pet” personality with animated visual feedback, while the open BLE standard makes it easy for makers to build their own custom versions.Sleep mode with ZZZs (left), Celebrate animation (middle), and Attention alert mode when waiting for approval (right)