Show HN: Rmux – A programmable terminal multiplexer with a Playwright-style SDK

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Show HN: Rmux – A programmable terminal multiplexer with a Playwright-style SDK

186

by shideneyu

Author here. RMUX started from a frustration: I've used tmux for years and got tired of scraping output with grep and sleeps to automate anything. So I rebuilt the multiplexer from scratch in Rust, with a programmable layer on top.

Two surfaces: a tmux-compatible CLI (~90 commands, your keybindings just work), and a typed async Rust SDK on the same daemon — stable pane IDs, structured snapshots, locator-style waits. The idea is Playwright-style automation, but for terminals.

Native on Linux, macOS, Windows (real ConPTY, no WSL).

Demos and docs at rmux.io. Happy to answer questions about the daemon protocol, ConPTY, or the SDK design.

pama
82d
Congrats on the launch. If emacs was unavailable and I needed tmux, I would try it. I am old school, and use emacs daemons for all shell multiplexing. The agents dont need explanations and know how to use emacsclient to create, read, or send inputs to named buffers that run the shells. Elisp is powerful, so manipulating windows is a breeze. Lots of people on tmux would benefit from this design though.
1. deangiberson
  11d
  Funny, I started vibing this (https://github.com/deangiberson/emacs-mux) yesterday on the train after playing with cmux for the day and thinking to myself there was nothing that emacs couldn't accomplish.
  The repo doesn't quite work yet. Many sharp corners. But the basic idea is there.
  pama, I'd be interested in hearing more about how you are using emacs for multiplexing. I'm trying to build up tooling for myself based around file and input workflows and I /really/ don't want to write a text editor and would prefer to stick with emacs.
  1. pama
    020m
    The key idea is to have many differently named shells. Typically, I group them by project (common prefix name), and the projects live in directories. I have some hacks to organize ibuffer, to split frames, to reflow buffers in the existing windows (eg to organize related project buffers (shells, magit, dired), or to show shells from multiple projects, or selected buffers, and so on). Emacs’ natural frame splitting and buffer selecting/switching commands are good enough if you dont display more than four buffers at a time, but soon you may need to show 5, 6, 8, 9, 10, 12, 15, 16, 18, 20, 24 or have funky arrangements, so you may collect functions to help along splitting n*m grids or keeping useful splits. The shells work very organically inside Emacs and you can still use it as a text editor. The so-called “dumb terminal” in M-x shell is a thing of beauty as it really is just a text buffer like any other; I think of it as a bash repl. If you are used to curses TUI commands it may not work, so for these rare occasions I also use eat (but tend to avoid). See also answer to a sibling comment.
2. evanjrowley
  12d
  Are there any guides on accomplishing this with Emacs? Perhaps something that might be useful for someone coming from Tmux?
  1. pama
    02d
    Not sure, tbh. I use emacs -daemon to start a server; emacsclient -nw to connect. I use ssh and start a server on the remote. I spawn multiple shells with infinte buffer size and dumb terminals (M-x shell) so I can seamlessly edit. (These are based on comint, a neat command interpreter.) I use my own hacks for named shells (https://github.com/pjj/Emacs-nsh) and for rearranging/splitting windows, but any of the latest powerful LLMs can help with ergonomic modifications to M-x shell or the various improved terminal emulators (vterm, eat, ansi-term) or with renaming and moving/splitting windows. The Emacs manual is excellent but long; worth it IMHO, but focus on things you use. The tutorial is quick; worth it. I avoid curses programs (fancy TUI) or write wrappers around some of them. I love the -p option in codex/claude/copilot.
3. sroerick
  32d
  I didn't know you could do this with Emacs
  1. scottyeager
    22d
    It's just too bad Emacs doesn't also include a decent text editor, right?
Sirental
232d
The website is a little too obviously made by Claude. The first thing I noticed is the classic "pill with pulsing green dot that says something is active or live" claudism.
1. shideneyu • OP
  42d
  The video of the front page is assisted by AI, I am not a vfx artist; please check rmux code architecture instead, I put a lot of efforts on it
florianist
12d
The paragraph on the website inviting us to switch to rmux from tmux claims that tmux is programmed in C++. tmux is made in C.
1. shideneyu • OP
  02d
  wupsy ! thanks, I just fixed it
kosolam
72d
Hey, I automate tmux all the time with send keys and capture.. how is your project improves vs tmux or zellij?
1. shideneyu • OP
  22d
  rmux is much faster than tmux or zellj, I did some internal benchmark and it's promising. rmux is a multiplexer engine, meaning that you can rewrite entirely zellij using rmux.. I created a mini zellij in a few hundred lines of rust. You can check the demoes on the repo
kloud
32d
Cool project, I like the idea of having tmux-compatible CLI. I used Zellij to get better UX, but many agent tools integrate with tmux. This way agent tools can still integrate tmux as a defacto standard for programmatic interface while having better interface for users.
But I wonder if tmux/rmux design is suboptimal since it couples session persistence and window management together. Do you have an opinion the design which separates the responsibilities? An example that pioneered this approach is abduco, and libghostty-based zmx being a modern implementation.
1. shideneyu • OP
  22d
btown
12d
Very cool! I think the hype around “agents are so good that you never actually need to see the underlying commands they are running or interact with the terminal session that they’re running” misses out on a lot of very important use cases, particularly around long running processes that may be shared across multiple agents. This will be very cool to see how best practices evolve!
1. shideneyu • OP
  02d
  Same ! TUI are becoming more and more mainstream so there is a need for automated multiplexing , not used by humans but by programs (and agents)
luizfwolf
32d
I found the project quite interesting but what's the advantage over just using tmux with a hotkey to send keys?
1. saghm
  02d
  Writing shell scripts to orchestrate things is not a particularly great experience. "Shell scripts are annoying to write compared to the programming languages we use for other things" isn't a universal opinion, but it's not exactly uncommon; I've heard plenty of people talk about switching to Python as soon as anything gets even moderately complex. (I often tend to go with the lines "my bar for when to switch to a real programming language is as soon as I have to write an if statement" and "the number of times I've had to write a for loop in bash is the same as the number of times I've had to google the syntax for a for loop in bash", which are only slight exaggerations). Having an actual library for interactions that isn't just a wrapper around the CLI seems like it would be a huge improvement for anything that isn't a one-off interaction.
cultofmetatron
142d
a week ago I was using cmux but its osx only and doen't work on remote terminals. then I switched to herdr which is great so far except its not s great at managing panes. I can't move them around or change ordering. now another terminal multiplexer. I'm getting whiplash.
all that said, none of the existing solutions are perfect and rust codebases are nice. how easy is it to reorder panes? is there a cli that lets me control the panel layout via a skill file and allow my opencode session to target and send data to other panes?
1. Oras
  42d
SwellJoe
32d
It's not clear to me what this does that tmux doesn't? Agents can already interact with tmux, so what does this provide?
1. gobdovan
  02d
  I think it's trying to be like a code-first/API alternative to Tmux. So instead of:
``` tmux new-session -d -s a
tmux send-keys -t a 'npm test' Enter
sleep 2
tmux capture-pane -p -t a ```
you'd do something like:
``` pane.send_text("npm test\n").await?;
  pane.wait_for_text("Tests passed").await?;
  let snapshot = pane.snapshot().await?; ```
  I don't know why it would be better for agents, maybe the author also works on an LLM agent harness.
0x1ceb00da
22d
Getting this error when installing from git bash:
$ curl -fsSL https://rmux.io/install.sh | sh rmux install: unsupported OS: MINGW64_NT-10.0-26200
1. shideneyu • OP
  01d
  Hello ! I just updated rmux, you can run the command again, it should work ! Thank you for your curiosity and support
hi083
122h
so is this, among other things, a bypass to the recent claude -p restriction Anthropic recently shared?
basically an api to a terminal?
1. shideneyu • OP
  012h
  exactly, claude-cli is just running behind the scenes in a detached way. rmux is parsing the output beautifully
chaoticbeard
01d
Does it support sixel or images at all?
cat-whisperer
02d
I used to use ghostty's applescript and built that into a claude skill. It worked like a charm. But this feels super interesting for programmability
notorandit
12d
Scriptable terminal multiplexer?
Interesting portable scripting thingy. But it would only work with portable tools, not just everything. Especially with Windows tools.
1. shideneyu • OP
  02d
  I wrote it for rust apps in mind, same usecase as for Ratatui. You’re right maybe I need to expose more tools with the cli
small_model
12d
Never had the need to do playwright automation for tmux, so not sure why I would use this above tmux which works well.
1. shideneyu • OP
  02d
  with rmux you can finally do acceptance/integration tests on your terminal user interfaces. tmux is made for humans, rmux is made for both humans and machines
joch
12d
Very nice!
I created `ygg`[0] a while back to easily spawn a new worktree when working with Claude/codex, and it also spawns that in a dedicated zellij tab. I think making the terminal multiplexer pluggable, so it would be easy to integrate something like this.
[0] https://github.com/joch/ygg
1. shideneyu • OP
  02d
  nice tool ! totally. rmux is lightweight, I believe it would be easy
DeathArrow
22d
1. ask Claude to rewrite X in Rust
2. ask Claude to make a website and claim R is better than X because it's Rust
3. advertise on HN, X and Reddit
4. ???
5. profit!
1. miroljub
  02d
  If the tokens are already burned, it's better for the environment to share the result for everyone to use it.
shadowfax92
22d
this might fit very nicely with gascity/gastown which orchestrates other coding agent over tmux.
currently, i finds it's tmux orchestration code is too complex.
will check it out
1. shadowfax92
  12d
  > got tired of scraping output with grep and sleeps to automate anything.
  curious, what was the usecase here?
yes_but_no
12d
Floating panes seems not possible, or are they?
1. shideneyu • OP
  02d
  Not part of the current version, it’s on my roadmap :)
elromulous
12d
Can someone describe the pros/cons vs zellij?
1. shideneyu • OP
  02d
  You can rewrite Zellij entirely with rmux , that's the main difference. I put a demo on the repo. Because rmux is an engine. I wrote it to be the multiplexer of multiplexers
eddyaipt
12d
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1. shideneyu • OP
  02d
  Yes exactly. And it enables integration testing too. I hope it will foster the release of more cool TUIs.
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