A Claude Code plugin that teaches the agent to operate cmux, a terminal multiplexer with first-class agent integration. Provides skill patterns and shell wrappers (cmux-send, cmux-read, cmux-send-key, cmux-grid, cfork) for the full sub-agent lifecycle: launch -> trust detection -> prompt -> completion detection -> result collection. Browser automation is covered to the depth needed for a single agent. Companion plugin cmux-team handles multi-agent orchestration on top of using-cmux. macOS / Linux only.