Ian Thomas

I've published the first two chapters of a new guide to Agentic Engineering Patterns - coding practices and patterns to help get the best results out of coding agents like Claude Code and OpenAI Codex simonwillison.net/2026/Feb/23/ag…

A few random notes from claude coding quite a bit last few weeks. Coding workflow. Given the latest lift in LLM coding capability, like many others I rapidly went from about 80% manual+autocomplete coding and 20% agents in November to 80% agent coding and 20% edits+touchups in December. i.e. I really am mostly programming in English now, a bit sheepishly telling the LLM what code to write... in words. It hurts the ego a bit but the power to operate over software in large "code actions" is just too net useful, especially once you adapt to it, configure it, learn to use it, and wrap your head around what it can and cannot do. This is easily the biggest change to my basic coding workflow in ~2 decades of programming and it happened over the course of a few weeks. I'd expect something similar to be happening to well into double digit percent of engineers out there, while the awareness of it in the general population feels well into low single digit percent. IDEs/agent swarms/fallability. Both the "no need for IDE anymore" hype and the "agent swarm" hype is imo too much for right now. The models definitely still make mistakes and if you have any code you actually care about I would watch them like a hawk, in a nice large IDE on the side. The mistakes have changed a lot - they are not simple syntax errors anymore, they are subtle conceptual errors that a slightly sloppy, hasty junior dev might do. The most common category is that the models make wrong assumptions on your behalf and just run along with them without checking. They also don't manage their confusion, they don't seek clarifications, they don't surface inconsistencies, they don't present tradeoffs, they don't push back when they should, and they are still a little too sycophantic. Things get better in plan mode, but there is some need for a lightweight inline plan mode. They also really like to overcomplicate code and APIs, they bloat abstractions, they don't clean up dead code after themselves, etc. They will implement an inefficient, bloated, brittle construction over 1000 lines of code and it's up to you to be like "umm couldn't you just do this instead?" and they will be like "of course!" and immediately cut it down to 100 lines. They still sometimes change/remove comments and code they don't like or don't sufficiently understand as side effects, even if it is orthogonal to the task at hand. All of this happens despite a few simple attempts to fix it via instructions in CLAUDE . md. Despite all these issues, it is still a net huge improvement and it's very difficult to imagine going back to manual coding. TLDR everyone has their developing flow, my current is a small few CC sessions on the left in ghostty windows/tabs and an IDE on the right for viewing the code + manual edits. Tenacity. It's so interesting to watch an agent relentlessly work at something. They never get tired, they never get demoralized, they just keep going and trying things where a person would have given up long ago to fight another day. It's a "feel the AGI" moment to watch it struggle with something for a long time just to come out victorious 30 minutes later. You realize that stamina is a core bottleneck to work and that with LLMs in hand it has been dramatically increased. Speedups. It's not clear how to measure the "speedup" of LLM assistance. Certainly I feel net way faster at what I was going to do, but the main effect is that I do a lot more than I was going to do because 1) I can code up all kinds of things that just wouldn't have been worth coding before and 2) I can approach code that I couldn't work on before because of knowledge/skill issue. So certainly it's speedup, but it's possibly a lot more an expansion. Leverage. LLMs are exceptionally good at looping until they meet specific goals and this is where most of the "feel the AGI" magic is to be found. Don't tell it what to do, give it success criteria and watch it go. Get it to write tests first and then pass them. Put it in the loop with a browser MCP. Write the naive algorithm that is very likely correct first, then ask it to optimize it while preserving correctness. Change your approach from imperative to declarative to get the agents looping longer and gain leverage. Fun. I didn't anticipate that with agents programming feels *more* fun because a lot of the fill in the blanks drudgery is removed and what remains is the creative part. I also feel less blocked/stuck (which is not fun) and I experience a lot more courage because there's almost always a way to work hand in hand with it to make some positive progress. I have seen the opposite sentiment from other people too; LLM coding will split up engineers based on those who primarily liked coding and those who primarily liked building. Atrophy. I've already noticed that I am slowly starting to atrophy my ability to write code manually. Generation (writing code) and discrimination (reading code) are different capabilities in the brain. Largely due to all the little mostly syntactic details involved in programming, you can review code just fine even if you struggle to write it. Slopacolypse. I am bracing for 2026 as the year of the slopacolypse across all of github, substack, arxiv, X/instagram, and generally all digital media. We're also going to see a lot more AI hype productivity theater (is that even possible?), on the side of actual, real improvements. Questions. A few of the questions on my mind: - What happens to the "10X engineer" - the ratio of productivity between the mean and the max engineer? It's quite possible that this grows *a lot*. - Armed with LLMs, do generalists increasingly outperform specialists? LLMs are a lot better at fill in the blanks (the micro) than grand strategy (the macro). - What does LLM coding feel like in the future? Is it like playing StarCraft? Playing Factorio? Playing music? - How much of society is bottlenecked by digital knowledge work? TLDR Where does this leave us? LLM agent capabilities (Claude & Codex especially) have crossed some kind of threshold of coherence around December 2025 and caused a phase shift in software engineering and closely related. The intelligence part suddenly feels quite a bit ahead of all the rest of it - integrations (tools, knowledge), the necessity for new organizational workflows, processes, diffusion more generally. 2026 is going to be a high energy year as the industry metabolizes the new capability.

Time outside of work has always been scarce for side projects. Over the holidays I took it upon myself to use some of the AI engineering skills I'd been using at work to see if I could get some side projects back up and running. This kickstarted my Vibe-uary ian-thomas.net/vibe-uary-or-h…

Sometimes you look up and realise it's nearly 3 years since you last blogged something. Today, I can say it's 1 day since I blogged something.

@bcherny Curious why you didn't do this already with Claude Code? What triggered you to do this with Cowork?

Cowork just organized 6 months of receipts into a categorized spreadsheet with monthly breakdowns. Pointed it at a folder. That’s it.

I'm Boris and I created Claude Code. Lots of people have asked how I use Claude Code, so I wanted to show off my setup a bit. My setup might be surprisingly vanilla! Claude Code works great out of the box, so I personally don't customize it much. There is no one correct way to use Claude Code: we intentionally build it in a way that you can use it, customize it, and hack it however you like. Each person on the Claude Code team uses it very differently. So, here goes.

@mprkhrst @amasad 👀

Convinced a university to scan Facebooks little red book on a $150k archival scanner The best PDF’s I could find were @amasad’s and a remastered version that were both low quality Reply if you’d like me to send you the link when it’s ready - should be the highest quality publicly available version to ever exist

@matryer This made me chuckle, love how niche 80s/90s British this joke is.

Why was light petting tolerated at swimming baths?

#GOTOEDADay #London & #Nashville huge hits for companies and developers who wanted to up their event driven architecture game. And now, we are back in London! May 14th is EDA Day London! Super early bird tickets are £49, more details to come! For now -> gotoldn.com/2024-eda-aws-d…

@editingemily Can you ever unhear it?

I can hear this gif.

@jeremy_daly Without saying anything, show me how long you’ve been on the internet.

Without saying anything, show me how long you’ve been on the internet.

For the ninth(!) year in a row, I will be releasing 25 programming puzzles over the first 25 days of December over on adventofcode.com! It's completely free thanks to AoC++ supporters and thanks to sponsors. If you want to check it out early, all past puzzles are still up!

Type the year you turned 10 in the gif search bar.

@boristane I don’t write code every day, but I do read it and share feedback on diffs. I’d say daily code involvement > daily writing, but not totally removing the writing

should a software architect write code daily?

Infoshare DEV Katowice completed for today, thank you to everyone that came to hear me speak! Looking forward to travelling to Gdynia for part 2 #InfoshareDEV

Bugs happen but it's rare you see a bug that grabs you so hard and makes you nod like a little dog.. CVE-2023-44487 did that for me good god what a bug and here's why

I picked up Leading Quality: How Great Leaders Delivery High-Quality Software and Accelerate Growth at the National Testing Conference last year and have constantly referred to it since. I particularly like how it presents Dan Ashby's manual vs automated testing framework

Enjoyed this one, and gmail put it in my priority inbox!

@_JamesWard @jdegoes @HappyPathProg Enterprises requires stability, breadth and depth of ecosystem. Academic & cutting edge features may be exciting for some, but unappealing for companies looking for stability & a large talent pool. Building a business is hard enough, don't waste cycles chasing language updates!

@_JamesWard @jdegoes @HappyPathProg This was a really good listen. A thoroughly pragmatic look at programming. I've dabbled with Scala repeatedly and love the premise (and promise) of it. Scala 3 is a lovely language. However, code is a means to an end, and ultimately economic viability and market forces win out.

Had such a great conversation with @jdegoes today about Scala, Rust, and Durable Computing! Check it out on the latest @HappyPathProg episode: podcasters.spotify.com/pod/show/happy…