Show HN: DanTerm – a fast macOS terminal emulator (compare with Ghostty, iTerm2)

danterm started out as a small AppKit wrapper around libghostty so I could get vertical tabs.

About 3-4 weeks ago, I decided to replace libghostty with my own Swift terminal engine implementation, and the whole project is just Swift with no third-party deps -- only Apple's swift-collection for a Deque impl.

I started with a naive correctness implementation that passed third-party tests, and then I incremented to the optimized release of today with things like a packed byte arena for scrollback that grows on demand.

The result is that it's an 8 MB application that sits at 52 MB with 10 empty tabs open and grows to just 250 MB when those tabs are filled with 10k lines each. (kitty: 240 -> 790 MB, ghostty 1.3: 780 -> 1400 MB). It also has the best pty throughput as measured by kitty's `kitten __benchmark__ --render`.

Perhaps most interestingly is that this project is my latest experiment in how to use rigor to automate high-quality software with LLMs. I use things like ADRs, a docs/research/ system, a review/revise cycle on plans, and multi-pass workflows to pay back debt and find code improvement opportunities.

For example: https://github.com/danneu/danterm/blob/749942ffa1198f520c8b7...

This project has put yet more writing on the wall, for me, that most software -- and then all software -- can be fully automated with just a human "taste-maker".

It has some cute features like:

- A `danterm <command>` CLI

- A replayable pty flight recorder (`danterm tape`)

- Usual fare like tabs, panes, themes, search, and a recovery system so that you can close danterm, reopen it, and it reads its prev state from disk. Even has a gimmicky todo system (per pane and per tab).

- A semantic model powered by shell/agent integrations where you notify danterm things like "command started (vim foo.sh)" and "agent waiting (claude code)". This seemed a lot more reasonable than trying to cleverly determine the state of the session from the pty stream.

- A companion iPhone app that lets me control danterm remotely over Tailscale

- A reusable Swift terminal engine that compiles on Linux (for fun, I started a gtk4 frontend)

Anyways, I hope it's interesting. It was a lot of work and it's my daily driver terminal.

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