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Comment by jaytaylor

19 days ago

(DTU creator here)

I did have an initial key insight which led to a repeatable strategy to ensure a high level of fidelity between DTU vs. the official canonical SaaS services:

Use the top popular publicly available reference SDK client libraries as compatibility targets, with the goal always being 100% compatibility.

You've also zeroed in on how challenging this was: I started this back in August 2025 (as one of many projects, at any time we're each juggling 3-8 projects) with only Sonnet 3.5. Much of the work was still very unglamorous, but feasible. Especially Slack, in some ways Slack was more challenging to get right than all of G-Suite (!).

Now I'm part way through reimplementing the entire DTU in Rust (v1 was in Go) and with gpt-5.2 for planning and gpt-5.3-codex for execution it's significantly less human effort.

IMO the most novel part to this story is Navan's Attractor and corresponding NLSpec. Feed in a good Definition-of-Done and it'll bounce around between nodes until it gets it right. There are already several working implementations in less than 24 hours since it was released, one of which is even open source [0].

[0] https://github.com/danshapiro/kilroy

16 comments

jaytaylor

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ukuina  19 days ago

Been toying around with DTs myself for a few months. Until December, LLMs couldn't correctly hold large amounts of modeled behavior internally.

Why the switch from Go to Rust?

  • jaytaylor  19 days ago

    I'm testing a theory that large-scale (LoC) generated projects in Rust tend to have fewer functional bugs compared to e.g. Go or Java because Rust as a language is a little stricter.

    I've not yet formed a full opinion or conclusion, but in general I'm starting to prefer Rust.

    Re: generalizing mocks, it sounds interesting but after getting full-fidelity clones of so many multi-billion dollar SaaS offerings, I really like it and am hooked. It pays nice dividends for developing using agentic coders at high scale. In a few more model releases having your own exhaustive DTU could become trivial.

    • mohsen1  15 days ago

      Hi there!

      I'm thinking about the same things and landed on Rust. I think we're at a very critical point in software development and would love to chat with you and share/learn ideas. Please let me know if you're interested.

knuckleheads  19 days ago

Are the digital twins open source anywhere, or available as a service somehow? They sound useful to use!

Zakodiac  19 days ago

[dead]

  • jaytaylor  19 days ago

    > The Go to Rust rewrite is interesting - was that driven by performance or more about the ecosystem/tooling for this kind of work?

    I'm testing a theory that large-scale (LoC) generated projects in Rust tend to have fewer functional bugs compared to e.g. Go or Java because Rust as a language is a little stricter.

    I've not yet formed a full opinion or conclusion, but in general I'm starting to prefer Rust.

    Re: generalizing mocks, it sounds interesting but after getting full-fidelity clones of so many multi-billion dollar SaaS offerings, I really like it and am hooked. It pays nice dividends for developing using agentic coders at high scale. In a few more model releases having your own exhaustive DTU could become trivial.