Show HN: Cmux – Coding Agent Multiplexer (github.com)

Coder Technologies released Cmux, a cross-platform desktop app that lets developers run and manage multiple agent workspaces in parallel for “agentic” coding tasks. It’s built for workflows like simultaneous code-review/refactor/new-feature branches, A/B testing different agent approaches, long-running background runs (auto-resuming after restarts or intermittent connectivity), and exploratory tangents isolated from a main workspace. The app centralizes git status, supports rich markdown outputs (Mermaid diagrams, LaTeX), and exposes UI/keybinds (including VIM input) to quickly switch, pause, or abandon agents — a practical productivity tool for teams and researchers iterating on agent-driven development. On the technical side Cmux uses a custom agent loop and multi-model orchestration (sonnet-4-*, gpt-5-*, opus-4-*) with UX patterns inspired by Claude Code — Plan/Exec mode, compact views, plus new ideas like opportunistic compaction and mode prompts. It’s aimed at developer-heavy usage: long-lived model runs, parallel evaluations, and experiment comparison. Cmux is currently in Preview (expect bugs/performance issues) and is distributed under the AGPLv3. Pre-built binaries are available for macOS (signed/notarized DMG for Intel & Apple Silicon) and Linux (AppImage); Windows support is forthcoming. Documentation and AGENTS.md cover setup and contributor guidelines.