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Agentic Engineering Patterns

simonwillison.net

41–50 of 341 posts

Re: Agentic Engineering Patterns

#41
I dont currently have confidence in TDD

A broken test doesn’t make the agentic coding tool go “ooooh I made a bad assumption” any more than a type error or linter does

All a broken test does it prompt me to prompt back “fix tests”

I have no clue which one broke or why or what was missed, and it doesnt matter. Actual regressions are different and not dependent on these tests, and I follow along from type errors and LLM observability

Re: Agentic Engineering Patterns

#42
The most important thing you need to understand with working with agents for coding is that now you design a production line. And that has nothing to do (mostly) with designing or orchestrating agents.

Take a guitar, for example. You don't industrialize the manufacture of guitars by speeding up the same practices that artisans used to build them. You don't create machines that resemble individual artisans in their previous roles (like everyone seems to be trying to do with AI and software). You become Leo Fender, and you design a new kind of guitar that is made to be manufactured at another level of scale magnitude. You need to be Leo Fender though (not a talented guitarrist, but definitely a technical master).

To me, it sounds too early to describe patterns, since we haven't met the Ford/Fender/etc equivalent of this yet. I do appreciate the attempt though.

Re: Agentic Engineering Patterns

#43

I dont currently have confidence in TDD A broken test doesn’t make the agentic coding tool go “ooooh I made a bad assumption” any more than a type error or linter does All a broken test does it prompt me to prompt back “fix tests” I have no clue which one broke or why or what was missed, and it doesnt matter. Actual regressions are different and not dependent on these tests, and I follow along from type errors and LL…

[flagged]

Re: Agentic Engineering Patterns

#44
post #6

I've experimented with agentic coding/engineering a lot recently. My observation is that software that is easily tested are perfect for this sort of agentic loop. In one of my experiments I had the simple goal of "making Linux binaries smaller to download using better compression" [1]. Compression is perfect for this. Easily validated (binary -> compress -> decompress -> binary) so each iteration should make a dent o…

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Re: Agentic Engineering Patterns

#45

I dont currently have confidence in TDD A broken test doesn’t make the agentic coding tool go “ooooh I made a bad assumption” any more than a type error or linter does All a broken test does it prompt me to prompt back “fix tests” I have no clue which one broke or why or what was missed, and it doesnt matter. Actual regressions are different and not dependent on these tests, and I follow along from type errors and LL…

[flagged]

Re: Agentic Engineering Patterns

#46

I dont currently have confidence in TDD A broken test doesn’t make the agentic coding tool go “ooooh I made a bad assumption” any more than a type error or linter does All a broken test does it prompt me to prompt back “fix tests” I have no clue which one broke or why or what was missed, and it doesnt matter. Actual regressions are different and not dependent on these tests, and I follow along from type errors and LL…

[flagged]

Re: Agentic Engineering Patterns

#47
post #20
post #12

Earlier quoted context omitted.

When was the last time you tried? I think trying agents to do larger tasks was always very hit or miss, up to about the end of last year. In the past couple of months I have found them to have gotten a lot better (and I'm not the only one). My experience with what coding assistants are good for shifted from: smart autocomplete -> targeted changes/additions -> full engineering

I’m not OP but every time I post a comment with this sentiment I get told “the latest models are what you need”. If every 3 months you are saying “it’s ready as long as you use the latest model”, then it wasn’t ready 3 months ago and it’s not likely to be ready now. To answer your question, I’ve tried both Claude code and Antigravity in the last 2 weeks and I’m still finding them struggling. AG with Gemini regularly…

I don’t think that’s true. Claude Opus 4.5/4.6 in Cursor have marked the big shift for me. Before that, agentic development mostly made me want to just do it myself, because it was getting stuck or going on tangents.

I think it can (and is) shifting very rapidly. Everyone is different, and I’m sure models are better at different types of work (or styles of working), but it doesn’t take much to make it too frustrating to use. Which also means it doesn’t take much to make it super useful.

Re: Agentic Engineering Patterns

#48

Yesterday I wrote a post about exactly this. Software development, as the act of manually producing code, is dying. A new discipline is being born. It is much closer to proper engineering. Like an engineer overseeing the construction of a bridge, the job is not to lay bricks. It is to ensure the structure does not collapse. The marginal cost of code is collapsing. That single fact changes everything. https://nonstruc…

The formal engineering disciplines are not defined by the construction vs design distinction so much as the regulatory gates they have passed and the ethical burdens they shoulder for society's benefit.

https://www.slater.dev/2025/09/its-time-to-license-software-...

Re: Agentic Engineering Patterns

#49

I use AI in my workflow mostly for simple boilerplate, or to troubleshoot issues/docs. I've dipped into agentic work now and again, but never been very impressed with the output (well, that there is any functioning output is insanely impressive, but it isn't code I want to be on the hook for complaining). I hear a lot of people saying the same, but similarly a bunch of people I respect saying they barely write code a…

> It feels a little tricky to square these up sometimes.

In my experience, this heavily depends on the task, and there's a massive chasm between tasks where it's a good and bad fit. I can definitely imagine people working only on one side of this chasm and being perplexed by the other side.

Re: Agentic Engineering Patterns

#50
post #20
post #12

Earlier quoted context omitted.

When was the last time you tried? I think trying agents to do larger tasks was always very hit or miss, up to about the end of last year. In the past couple of months I have found them to have gotten a lot better (and I'm not the only one). My experience with what coding assistants are good for shifted from: smart autocomplete -> targeted changes/additions -> full engineering

I’m not OP but every time I post a comment with this sentiment I get told “the latest models are what you need”. If every 3 months you are saying “it’s ready as long as you use the latest model”, then it wasn’t ready 3 months ago and it’s not likely to be ready now. To answer your question, I’ve tried both Claude code and Antigravity in the last 2 weeks and I’m still finding them struggling. AG with Gemini regularly…

Agree, it’s strange, I will just assume that the people who say this are building react apps. I still have so much ”certainly, I should not do this in a completely insane way, let me fix that” … -400+2. It’s not always, and it is better than it was, but that’s it.
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