CMUX Terminal Is Making Me Rethink How We Code

Here's a weird flex: developer and YouTuber Theo has used terminal multiplexers for longer than he hasn't. Since he was 15, actually—GNU screen at first, then tmux for the past decade and a half. That's the kind of muscle memory that makes switching tools feel like relearning how to type.

But he just did it anyway. And not because Ghostty, his terminal of choice, suddenly got bad. Ghostty is still "really fast, really good, reliable, customizable, open source, well-maintained, all the things you would want your terminal to be," according to Theo. The problem isn't the tool. It's that the work itself has changed shape.

When Your Workflow Outgrows Your Tools

Theo describes his current work as branching more, going up and down more, getting stranger in how things happen in parallel. He's juggling more projects simultaneously than ever before—different codebases, different dev servers, different git branches, AI coding assistants running in some terminals but not others. The mental model for organizing this work across traditional terminal windows, tabs, and panels was breaking down.

"The hierarchy of the work I am doing does not map well to things like a terminal multiplexer," he explains. That's when he found CMUX, a new terminal built on libghosty—the core library that powers Ghostty—by the team at Manaflow.

Full disclosure: Theo invested in Manaflow before they even started building CMUX, which means he's now financially tied to a company that's building open-source software for free. His exact words: "If I don't want to lose all of my money to open source projects, we're going to have to make a little now." So yes, there's skin in the game here.

What Makes CMUX Different

The pitch is straightforward: CMUX adds project-level organization to your terminal. Instead of just having windows and panes, you get a sidebar with different projects. Each project can have its own set of terminals, tabs, and splits. Theo can have one workspace for T3 Code, another for his sandbox experiments, another for benchmarking work, and jump between them with keyboard shortcuts.

Within each project, he's set up his own hierarchy. One terminal runs Claude Code (Anthropic's AI coding assistant). Behind it in another tab, his dev server runs quietly where he can check it when needed but it's not taking up screen real estate. On the other side, a dedicated git terminal for all the branch management and PR filing he does constantly.

"It's very easy to hop between apps and see what's going on in each of them," Theo says. When he holds down the command key, hotkeys appear on everything showing him exactly how to navigate. The organizational model just... fits how he's actually working now.

Even Mitchell Hashimoto, Ghostty's creator, seems excited about this direction. Theo quotes him: "Ghosty the app has always been a glorified tech demo for lib ghosty which is what he planned and hoped would really take over the world eventually with a diverse set of terminal adjacent things focused on specific goals and ideas and that's what's happening."

The Rough Edges

But CMUX isn't perfect, and Theo's brutally honest about where it falls apart. There's an annoying bug where his zsh status line doubles up, and every time he clears the terminal or hits enter on an empty line, another line appears. He's just... living with it. "It's the worst. It annoys me so much."

Then there's the built-in browser. CMUX tries to handle web links by opening them in an integrated Safari webview. Sounds neat in theory. In practice? It doesn't have his auth, his cookies, or extension support, which means he can't even use 1Password to sign into things. This broke one of his most common workflows: pushing a git branch and opening a link to file a PR, something he does "dozens of times a day." He eventually found the setting to turn off the built-in browser and went back to using regular Chrome.

"The only thing I like CMUX for is how it collapses the terminal side of this," Theo admits. "They have also attempted to solve the browser problem and I hate it."

What Comes Next

Here's where things get interesting. Theo isn't just using CMUX—he's thinking about what this category of tool could become. He's recently gotten obsessed with Niri, a "papering" window manager where new windows don't steal space from existing ones. Instead of dividing your screen into smaller and smaller tiles, each window maintains its own size and you scroll through them like sheets of paper.

He wants that same concept inside CMUX. Imagine each project in the sidebar having an infinitely scrollable canvas of terminals. You could three-finger swipe left and right between them, go vertical for different tasks within a project, and never feel cramped because opening a new terminal doesn't shrink the old ones.

And then he goes further: what if it wasn't just terminals? What if you could integrate actual Chrome—not a janky webview, but your real Chrome profile with all your extensions and auth—right into this workspace model? Your terminal, your editor, and your browser, all organized by project, all in one place.

"I can't stop thinking about this now that I've thought about it," Theo says.

Mitchell Hashimoto has been "talking shit about the GUIs for managing agents" because most of them suck, according to Theo, who's been forcing himself to try various AI coding interfaces. He thinks they all miss the mark. "I asked him to tell me every problem he has so that we can make sure we do this properly with T3 code. I'm very excited to potentially get to build his dream app because he's already built so many of mine."

The problem space is clear: developers are working differently now. More projects in parallel, AI assistants in the mix, context switching that's both more frequent and more complex. Traditional terminal multiplexers were built for a different era of work. CMUX is a first attempt at building for how we actually code in 2025. It's far from finished, rough around the edges, and missing features Theo considers essential.

But it's also the first tool in years that made him switch terminals after using the same setup for a decade. That's not nothing. And judging by where his head is at—imagining nested infinite canvases with full Chrome integration—we're probably still in the very early innings of figuring out what a modern developer workspace should actually look like.

Tyler Nakamura is Buzzrag's Consumer Tech & Gadgets Correspondent