proton-cli

A single-binary CLI tool that provides access to five Proton services from the terminal on Linux, macOS, and Windows. It handles authentication and encryption locally using Proton's own libraries, ensuring your keys never leave your machine. The tool supports mail management, file operations, calendar events, password storage, and contact management through a consistent command structure.

Designed for developers and power users who prefer terminal workflows, proton-cli outputs JSON and YAML, supports piping and cron jobs, and includes dry-run modes for state-changing operations. The maker reports that LLMs assisted in writing much of the codebase, backed by an extensive test suite covering hundreds of API endpoints.