Show HN: jmux – tmux-based development environment for humans and coding agents
github.comI've been a tmux user for years. When I started running 5-10 Claude Code sessions in parallel, I tried the tools that are out there: Conductor, cmux, the GUI orchestrators. None of them felt right. They either wanted me to leave tmux entirely for a 100MB+ Electron app with its own editor and Git workflow, or they were thin wrappers that didn't solve the actual problem: I need to parallelize my entire development environment, agents, editors, servers, logs, and keep track of all of it.
So I built jmux. It turns tmux into a parallel development environment. Every session, every agent, every running process, visible and navigable from one terminal. When Claude Code completes a response, an orange flag appears on that session. Switch to it, review the work, move on. No context switching to a different app. No learning a new workflow. It's still tmux underneath.
The key decision was to build on tmux instead of replacing it. My ~/.tmux.conf still works. My neovim setup still works. My keybindings, plugins, prefix key, etc, all of it carries over. jmux just makes it all work at scale.
What it does:
- Run Claude Code, Codex, aider. Any agent, directly, in parallel
- Attention flags. Know the moment an agent finishes without watching every pane
- Instant switching between sessions (Ctrl-Shift-Up/Down, no prefix key)
- Auto-groups sessions by project and git branch
- Works with your existing tmux config, editor, and tools
- No SDK, no API wrappers. First-party tools, no middleman.
What it doesn't do:
- No built-in editor (I use neovim btw)
- No built-in Git (use yours)
- No agent protocol/wrapper (run them directly in the terminal)
~1800 lines of TypeScript, ~0.3 MB installed. MIT licensed.
Landing page: https://jmux.build
Github: https://github.com/jarredkenny/jmux Well, your timing is perfect. Conductor's been crashing on startup all morning, and nothing I try fixes it. Ah shoot sorry to hear that! I’m one of the creators. Can you email me charlie@conductor.build and I can help debug it for you? :) Tried this on my WSL2 machine (which is my main machine now) and I can now forget my Mac again because of cmux. Thanks for this. Happy to hear this works in WSL! I'm using claude-squad for the same purpose at the moment, will try this one out Can't wait to give this a shot, looks excellent! does jmux handle the case where two agents need to modify the same file? Not in anyway that worktrees and coding agents don't already. jmux follows the Unix philosophy which means you compose it with the tools for your workflow. I use a git worktree per thing I am working on and run claude code in the worktree. Legend