ccNexus is a multi-protocol AI API proxy/gateway that provides intelligent endpoint rotation, failover, and format conversion between Claude, OpenAI Chat, OpenAI Responses, and Gemini APIs. It operates as both a desktop application (built with Wails v2, providing a native GUI with system tray integration, auto-updater, and terminal launcher) and a headless server (with an embedded zero-dependency Web UI for management). The system manages API credentials via a token pool with automatic refresh and rate-limit tracking, stores usage statistics in SQLite, and supports backup/restore across local, WebDAV, and S3 providers. The architecture is modular: a core proxy layer handles request routing, authentication, and streaming; a transformer layer converts between API formats using a plug-in registry; a storage layer abstracts persistence behind adapters; and service modules provide endpoint management, statistics aggregation, and backup orchestration. The desktop frontend is a vanilla JavaScript SPA with extensive theming and i18n support, while the server Web UI is a separate but functionally parallel implementation. Key capabilities include: multi-endpoint failover with configurable retry and rotation strategies, real-time format conversion with thinking block and tool call mapping, Codex token pool credential management with automatic refresh and cooldown, usage statistics with daily/weekly/monthly trends and monthly archives, WebDAV-based multi-device configuration sync, and a comprehensive REST API for remote management. The codebase demonstrates strong engineering practices with contract tests, security-conscious redaction of secrets in logs and API responses, and thread-safe configuration management.