Weeknotes for the week finishing Friday, 27th February 2026.

This week felt like a tipping point: I started using an LLM to write code.

Before this week, I’d used ChatGPT’s web app to ask “How do I?” questions.

  • How do I count the number of NaN values in a numpy array?
  • How do I parse a date string into a Date object in JavaScript?
  • How do I run a command for every commit in a range?

These are questions that at some point or other I’ve answered myself. Sometimes I’ve read the docs. Sometimes I’ve Googled some keywords and sifted through the results. Often I’ve done both. Alas, I’ve forgotten the answers and whilst I’d like to refresh my numpy, JavaScript, and Git knowledge, I need the answers now. In some cases, that’s because I want to do the right thing before moving on: a mistake when counting the number of NaN values would mean more time spent debugging; incorrectly parsing a date string would mean a bug. In others, that’s because I’m scratching an itch: I could checkout each commit and run the command, but is there a better way? I’m not going to spend my evenings and weekends finding out. I’m 44 and have a young family. I don’t have evenings and weekends.

That was before this week. This week, I used Codex to write code. You’re looking at it now. I used Codex to write the HTML and CSS for my website. I could have written it myself, but I don’t write much HTML and CSS day-to-day and I don’t have a clear picture of what good front-end code looks like.

At work, I also used Codex to write front-end code, but with Bootstrap. The Bootstrap docs are excellent: easy to navigate, loads of examples. But I wanted a modal and as with the “How do I?” questions, I wanted to do the right thing before moving on. Incorrectly nesting a .modal within a .modal-dialog would mean a bug (they’re the other way around). I don’t have evenings and weekends. I need the answers now.

I reviewed the code for my website and the modal just as I would review the code in a PR. My sense is that Codex has a much clearer picture of what good front-end code looks like than I do. I learnt a lot, but I feel uneasy. Some thoughts:

  • What are the environmental impacts of using LLMs?
  • And the social impacts? There are haves and have-nots.
  • And the legal impacts? LLMs can write good front-end code because they’ve been trained on open-source projects.
  • Do LLMs disproportionately benefit me, a senior software engineer? It seems so. (Thank you for the link, Katie.)
  • What are the security implications of using LLMs? Codex can read the contents of my .env file.
  • What are the blub studies implications of using LLMs? Detailed mental models are valuable; fiddly technical details aren’t?

Time’s up!