I built a programming language using Claude Code

One thing I'd add: even with good specs, the agent still cuts corners in ways that are hard to catch. It'll implement a feature but quietly add a fallback that returns mock data when the real path fails. Your app looks like it works. It doesn't. You find out in production.

Or it'll say "done" and what it did was add a placeholder component with a TODO. So now I have trust issues and I review everything, which kind of defeats the "walk away from the computer" part.

The "just one more prompt" loop is so true lol.

Impressive. As a practical matter, one wonders what th point would be in creating a new programming languages if the programmer no longer has to write or read code.

Programming languages are after all the interface that a human uses to give instructions to a computer. If you’re not writing or reading it, the language, by definition doesn’t matter.

That is the part of the post that stuck with me, because I've also picked up impossible challenges and tried to get Claude to dig me out of a mess without giving up from very vague instructions[1].

The effect feels like the Loss-Disguised-As-Win feeling of the video-games I used to work on at Zynga.

Sure it made a mistake, but it is right there, you could go again.

Pull the lever, doesn't matter if the kids have Karate at 8 AM.

[1] - https://github.com/t3rmin4t0r/magic-partitioning

It’s missing all the heart, the soul, of deciding and trading off options to get something to work just for you. It’s like you bought a rat bike from your local junkyard and are trying to pass it off as your own handmade cafe racer.

That said, the core value of the software wouldn't exist without a human at the helm. It requires someone to expend the energy to guide it, explore the problem space, and weave hundreds of micro-plans into a coherent, usable system. It's a symbiotic relationship, but the ownership is clear. It’s like building a house: I could build one with a butter knife given enough time, but I'd rather use power tools. The tools don't own the house.

At this point, LLMs aren't going to autonomously architect a 400+ table schema, network 100+ services together, and build the UI/UX/CLI to interface with it all. Maybe we'll get there one day, but right now, building software at this scale still requires us to drive. I believe the author owns the language.

In all seriousness, this is great, and why not? As the post said, what once took months now takes weeks. You can experiment and see what works. For me, I started off building a web/API framework with certain correctness built in, and kept hitting the same wall: the guarantees I wanted (structured error handling, API contracts, making invalid states unrepresentable) really belonged at the language level, not bolted onto a framework. A few Claude Code sessions later, I had a spec, then a tree-sitter implementation, then a VM/JIT... something that, given my sandwich-generation-ness, I never would have done a few months ago.

That said, it's a lot of words to say not a lot of things. Still a cool post, though!

I've been trying a new approach I call CLI first. I realized CLI tools are designed to be used both by humans (command line) and machines (scripting), and are perfect for llms as they are text only interface.

Essentially instead of trying to get llm to generate a fully functioning UI app. You focus on building a local CLI tool first.

CLI tool is cheaper, simpler, but still has a real human UX that pure APIs don't.

You can get the llm to actually walk through the flows, and journeys like a real user end to end, and it will actually see the awkwardness or gaps in design.

Your commands structure will very roughly map to your resources or pages.

Once you are satisfied with the capability of the cli tool. (Which may actually be enough, or just local ui)

You can get it to build the remote storage, then the apis, finally the frontend.

All the while you can still tell it to use the cli to test through the flows and journeys, against real tasks that you have, and iterate on it.

I did recently for pulling some of my personal financial data and reporting it. And now I'm doing this for another TTS automation I've wanted for a while.

It has not had any issues at all writing objc3 code

I really liked that part - the house always wins.

However, I fear that agents will always work better on programming languages they have been heavily trained on, so for an agent-based development inventing a new domain specific language (e.g. for use internally in a company) might not be as efficient as using a generic programming language that models are already trained on and then just live with the extra boilerplate necessary.

I haven't read any farther than this, yet, but this made me stutter in my reading. Isn't a comparison just a function that takes two arguments and returns a third? How is that different from "+"?

Congratulations on getting to the front page ;)

  fn read_float_literal(&mut self) -> &'a str {
    let start = self.pos;
    while let Some(ch) = self.peek_char() {
      if ch.is_ascii_alphanumeric() || ch == '.' || ch == '+' || ch == '-' {
        self.advance_char();
      } else {
        break;
      }
    }
    &self.source[start..self.pos]
  }

At the end of the day, I threw out all of the code the AI generated and wrote it myself, because the AI struggled to produce code that was functional to spec, much less code that would allow me to easily extend it to other kinds of future operators that I knew I would need in the future.

This is such an interesting statement to me in the context of leftpad.

I mean, they may be right but there is also a big opportunity for this being Gell-Mann amnesia : "The phenomenon of a person trusting newspapers for topics which that person is not knowledgeable about, despite recognizing the newspaper as being extremely inaccurate on certain topics which that person is knowledgeable about."

Step #2 is: get real people to use it!

Who the hell is going to use it then? You certainly won't, because you're dependent on AI.

The "more on that later" was unit tests (also generated by Claude Code) and sample inputs and outputs (which is basically just unit tests by a different name).

This is... horrifically bad. It's stupidly easy to make unit tests pass with broken code, and even more stupidly easy when the test is also broken.

These "guardrails" are made of silly putty.

EDIT: Would downvoters care to share an explanation? Preferably one they thought of?