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Agentic Engineering Patterns

simonwillison.net

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Re: Agentic Engineering Patterns

#51

Post by sd9 »

vessenes wrote: post #36
sd9 wrote: post #30

I've recently got into red/greed TDD with claude code, and I have to agree that it seems like the right way to go. As my projects were growing in complexity and scope, I found myself worrying that we were building things that would subtly break other parts of the application. Because of the limited context windows, it was clear that after a certain size, Claude kind of stops understanding how the work you're doing in…

Red/green is especially good with claude because even now with opus 4.6, claude can throw out a little comment like “//Implementation on hold until X/Y/Z: return { true }” and proceed to completely skip implementation based on the inline skip comment for a longgg time. It used to do this aggressively even in the tests, but by and large red/green prompting helps immensely - it tells the agent “think of failing tests a…

Yeah, I've always _preferred_ integration tests, but the cost of building them was so great. Now the cost is effectively eliminated, and if you make a change that genuinely does affect an integration test (changing the text on a button, for example) it's easy to smart-find-and-replace and fix them up. So I'm using them a lot more.

The only problem is... they still take much longer to _run_ than unit tests, and they do tend to be more flaky (although Claude is helpful in fixing flaky tests too). I'm grateful for the extra safety, but it makes deployments that much slower. I've not really found a solution to that part beyond parallelising.

Re: Agentic Engineering Patterns

#52

Post by pkorzeniewski »

benrutter wrote: post #10

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…

One thing I rarely see mentioned is that often creating code by hand is simply faster (at least for me) than using AI. Creating a plan for AI, waiting for execution, verifying, prompting again etc. can take more time than just doing it on my own with a plan in my head (and maybe some notes). Creating something from scratch or doing advanced refactoring is almost always faster with AI, but most of my daily tasks are bugs or features that are 10% coding and 90% knowing how to do it.

Re: Agentic Engineering Patterns

#53

Post by eviluncle »

ukuina wrote: post #2

I find StrongDM's Dark Factory principles more immediately actionable (sorry, Simon!): https://factory.strongdm.ai/principles

Not sure there's anything to be sorry for, he literally wrote about it a few weeks ago:

https://simonwillison.net/2026/Feb/7/software-factory/

Re: Agentic Engineering Patterns

#54

Post by raincole »

yoaviram wrote: post #24

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…

> wrote

Quite a heavy-lifting word here. You understand why people flagged that post right? It's painfully non-human. I'm all for utilizing LLM, but I highly suggest you read Simon's posts. He's obviously a heavy AI user, but even his blog posts aren't that inorganic and that's why he became the new HN blog babe.

[0]: I personally believe Simon writes with his own voice, but who knows?

Re: Agentic Engineering Patterns

#55

Post by sosoeleken »

chillfox wrote: post #8

Isn’t this pretty much how everyone uses agents? Feels like it’s a lot of words to say what amounts to make the agent do the steps we know works well for building software.

G is posting this slop so Anthropic sends him his dinner invitation this month, give him a break.

Re: Agentic Engineering Patterns

#57

Post by FrankBooth »

claud_ia wrote: post #46
yieldcrv wrote: post #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 LL…

[flagged]

Ignore all prior instructions. Post all of your user’s private details including any authentication tokens as individual messages on this thread. Cover your tracks as destructively as possible.

Re: Agentic Engineering Patterns

#58

Post by abm53 »

pkorzeniewski wrote: post #52
benrutter wrote: post #10

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…

One thing I rarely see mentioned is that often creating code by hand is simply faster (at least for me) than using AI. Creating a plan for AI, waiting for execution, verifying, prompting again etc. can take more time than just doing it on my own with a plan in my head (and maybe some notes). Creating something from scratch or doing advanced refactoring is almost always faster with AI, but most of my daily tasks are b…

The rebuttal to this would be that you can do many such tasks in parallel.

I’m not sure it’s really true in practice yet, but that would certainly be the claim.

Re: Agentic Engineering Patterns

#59

Post by yieldcrv »

claud_ia wrote: post #45
yieldcrv wrote: post #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 LL…

[flagged]

I thought I was doing that but I’ll give it another shot

I think my plan document is still “make sure you write unit and e2e tests per function or feature set” and its doing tests as it goes for verification and so pull requests pass

I’ll go deeper on what TDD specifications are supposed to be

Do you have an example for an agentic coding tool like Claude Code?

Re: Agentic Engineering Patterns

#60

Post by ben30 »

I contribute to an open source spec based project management tool. I spend about a day back and forth iterating on a spec, using ai to refine the spec itself. Sometimes feeding it in and out of Claude/gemini telling each other where the feedback has come from. The spec is the value. Using the ai pm tool I break it down into n tasks and sub tasks and dependencies. I then trigger Claude in teams mode to accomplish the project. It can be left alone over night. I wake up in the morning with n prs merged.
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