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

Show HN: Rmux – A programmable terminal multiplexer with a Playwright-style SDK(github.com)

64 points by shideneyu 2 hours ago | 39 comments

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.

kloud 35 minutes ago |

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.

shideneyu 9 minutes ago | |

I thought I was too zealous because I created 11 crates respecting single responsibility principles.. I would have been all in to risk it further and separating responsibilities for session and window management but it would have diverged too much from tmux. I wanted a 1-1 port for now

0x1ceb00da 38 minutes ago |

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

cat-whisperer 38 minutes ago |

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

florianist 1 hour ago |

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.

shideneyu 1 hour ago | |

wupsy ! thanks, I just fixed it

cultofmetatron 2 hours ago |

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?

qudat 31 minutes ago | |

I built https://zmx.sh to make it easier to interact with your terminal sessions programmatically. 1 window = 1 session which might feel like a negative but it makes programmatic access easy and agents can use it just by pointing it at the zmx help command. Basically, an agent just needs 2 commands (run and write) for full control and the commands are synchronous so you don’t need to do any polling.

Oras 1 hour ago | |

I started using cmux a month ago and it had made my life a lot easier. Finally I have a pane with all my projects open all the time, I can switch between them, have multiple terminals for each one.

What do you mean by remote terminals?

cultofmetatron 1 hour ago | | |

my plan is to eventually move my entire workflow to a remote workmachine over ssh. with kernal, I can automate all my smoketests entirely from a headless machine rendering my laptop overkill to run agentic workflows. I'd rather be using it to watch movies, learn new stuff or hand code in my downtime. if your workflow requires cmux, you're stuck running your agents on your local machine.

To be clear, That doesn't make cmux bad. if you WANT to do everythign on your mac, cmux is fantastic. its just not designed with the remote ssh control use case in mind.

shideneyu 1 hour ago | |

no skill file, you get the same 90 commands of tmux. and if you build a rust app you can have many more cool stuff like "wait for" some text to appear, asyncly

cultofmetatron 1 hour ago | | |

well it looks great so far but Its a no go for me for now until you have at least a cli that a coding harness can use to drive it. thats going to be the killer feature going forward for all these multiplexers. last week I vibecoded a plugin that lets me open a line specific input box that sends the context of my code along with my prompt into my opencode session running on a seperate pane. its a game changer when it comes to moving faster.

excited to check back in on the progress as you work on it though! I think these kinds of tools are going to be much more relevant going forward as we all move to agentic workflows.

DeathArrow 46 minutes ago |

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!

miroljub 30 minutes ago | |

If the tokens are already burned, it's better for the environment to share the result for everyone to use it.

Sirental 2 hours ago |

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.

ookblah 58 minutes ago | |

"site made by ai" is the new "bootstrap template" criticism that honestly gets tiring after a while. just read the content.

shideneyu 2 hours ago | |

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

redrove 2 hours ago | |

I’m genuinely interested in what you find to be the problem with that?

It’s a landing page.

cultofmetatron 1 hour ago | |

commonlisp (sbcl) is one of the best sleeper techs out there. one of those if you're in the know type industry secrets. part of it is because their website looks like something out of the 90's. clearly having a nice website and some level of marketing is necessary to get adoption. Im more than happy to see devs use AI to automate that so they have more time to focus on their creations.

alcasa 1 hour ago | | |

Isn't lisp getting advertisement every couple months here or so. After so many decades I don't believe the reason lisp doesn't have traction is just marketing.

Oras 1 hour ago | |

and why this is a problem? I found the landing page covering exactly what the product does, with nice demos and examples.

stefanfisk 1 hour ago | |

Not to mention those absolutely horrible scroll animations.

shideneyu 1 hour ago | | |

you don't like parallax effects ? maybe I'm too 2010 for you

jarym 1 hour ago | |

So?

shideneyu 1 hour ago | | |

@jarym what don't you like with the homepage ? I am curious how I can improve

luizfwolf 2 hours ago |

I found the project quite interesting but what's the advantage over just using tmux with a hotkey to send keys?

shideneyu 1 hour ago | |

windows support, and the sdk. native async "wait until" something appears on your terminal, so you don't spam send-keys

kosolam 2 hours ago |

Hey, I automate tmux all the time with send keys and capture.. how is your project improves vs tmux or zellij?

Galanwe 1 hour ago | |

I don't get it as well, everything mentioned in the readme is already trivially possible with tmux or zellij

shideneyu 1 hour ago | | |

windows support + async + public sdk. You can rewrite zellij with rmux, but not the opposite. rmux is a multiplexer engine

shideneyu 1 hour ago | |

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

kosolam 1 hour ago | | |

But wait, I’m a user of tmux or zellij which for me was basically another tmux and I went back to tmux eventually. I’m not looking to develop another tmux or something. Is this project more of a library to create tmux like apps?

noodletheworld 2 hours ago | |

I mean, the obvious immediate answer is “windows”, which tmux flat out doesn't support (except via WSL and a shared mount).

small_model 2 hours ago |

Never had the need to do playwright automation for tmux, so not sure why I would use this above tmux which works well.

shideneyu 2 hours ago | |

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

elromulous 1 hour ago |

Can someone describe the pros/cons vs zellij?

shideneyu 1 hour ago | |

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