Martin Fowler and Kent Beck on AI: What Carries Over from Agile, and What They Have to Give Up

Open on YouTube ↗
Overview

At the Pragmatic Summit, a conference otherwise full of AI startups, the host brought Martin Fowler and Kent Beck on stage. Both were among the 17 signatories of the Agile Manifesto 25 years ago. The host asked them what they have seen across decades of technology shifts, what the rollout of Agile suggests about the rollout of AI, and what engineers who care about craft should do now. Neither speaker claimed to know how the AI transition will end. Both argued that the habits of verification, skepticism, and good design they have promoted for decades still matter. Beck also admitted that part of what he loved about programming no longer pays off.

19 min read

What stuck from Agile, TDD, and refactoring

The host opened by asking which of their ideas engineers still thank them for. Fowler said he hadn't really reflected on it. People talk to him about Agile in general or about refactoring, since he wrote that book, but he couldn't name a specific piece that stood out. Beck said he gets "Thank you so much for test-driven development," and also hears that TDD ruined someone's life: their dog left and their house burned down, and it was all his fault. The host said they had personally gone back and forth on TDD, and suggested these practices were meant to be provocative and to push people.

Fowler then described a conversation from the day before with someone pushing hard on AI. That person thanked them for 20 years of promoting TDD, because tests have become very important now that there are AI agents. Fowler said he is suspicious of feedback like this precisely because he wants it to be true, and he tends to ask himself whether he is just making it up. Still, the reasoning made sense to him: with "a big powerful genie" at hand, you have to learn how to verify that it is doing the right thing for you. Beck added that this is what they have been practicing for 25 years. Fowler joked that he isn't a big powerful genie himself, but he still needed tests to check he was doing the right thing.

What they are working on now

The host said someone on LinkedIn had complained that the conference was inviting authors who were out of touch with technology, and asked both speakers what their day-to-day work looks like.

Fowler said that after finishing the second edition of Refactoring, five or six years ago, he considered writing another book. He has several half-written ones. He decided against it and chose instead to work with people who are still doing real work on real projects and writing real code, and to help them publish what they learn. That work is mostly on martinfowler.com, which he likes because he controls it and no big corporation can take it over. Since AI arrived, he has focused on capturing people's workflows in detail. He wants to know what conversations they have with the genies (Beck's term, he noted), what they look for when reviewing output, and above all which decisions humans still make and how that flow of decisions is changing. He stressed that his interest lies in what his colleagues are doing, and his job is spreading it.

Beck described his personal mission as helping geeks feel safe in the world, and said they don't feel safe right now, for some good reasons and some bad ones. For 25 years, he said, they had the answers. If a team had too many bugs, you told them to write tests. If they couldn't write tests, you showed them how to design so they could. It was like pressing play on a recording. That has changed: "at this moment nobody knows the answers to anything." So Beck has gone back into explore mode, partly out of his own curiosity, to find out what makes people effective with the new tools. He then wants to show the next generation, who are used to looking up answers in a book, how that search is done. Looking it up worked for 20 years, he said, but it hasn't worked in the last year and won't for a long time. In his view, seniors owe it to others to show not only how to use the tools effectively but how to figure out how to use them effectively, which he called "a whole different set of skills."

Historical analogies: OO, the internet, Agile, the microprocessor

Asked whether any earlier technology shift felt as unpredictable as AI, Fowler said nothing has hit with this magnitude and called it "a whole size difference." At a smaller scale, he pointed to the growth of object-oriented languages, which scared many people, though not the two of them, since they were part of it. He also named the internet and Agile itself. You could measure Agile's impact, he said, by how hard organizations resisted it. The key difference, in Fowler's view, is that with all those earlier shifts they had to persuade people the change mattered. That was true even of the internet, since some people didn't think it was important. With AI, there is essentially no argument about its importance, and you cannot put blinkers on to deny it.

Beck offered a different analogy: the microprocessor. Before it, computers were big boxes you couldn't move, and buying another one meant mortgaging your house again. He was a kid in Silicon Valley, with a programmer father, when the Intel 4004 came out, and he remembered the reaction: that's a computer? The possibilities suddenly opened up for anyone who could write software or design hardware around it. He sees AI partly as a similar expansion of imagination. He described his own "ridiculously ambitious" projects, including a persistent Smalltalk and library-quality Rust code. He tries anything he can imagine, many attempts fail, and he considers that part of the process. He also stressed that this is not the first time "the heavens have opened" with a flood of new opportunities.

Skepticism about skepticism, and the smallest experiment

The host asked what separated the experienced people who thrived in earlier shifts from those left behind. Fowler said each shift had a mix of people chasing the hype and people insisting it was nothing special. You need a balance of skepticism and curiosity, he said, and you apply it selectively. He has been completely skeptical of some big changes, blockchain for instance, and said that skepticism is well founded after years of watching the industry push snake oil. But he explained his rule: his skepticism has to be "absolute and total," so he must also be skeptical about his skepticism. That takes curiosity, because you have to ask how to probe for signs that something real is emerging.

Beck turned this into a practical question: what is the smallest experiment I can run to verify, to my own satisfaction, whether a claim is true? He noted that everyone's threshold for satisfaction differs. He said that skill has become "a thousand times more valuable" in the last year.

Why first impressions of AI can mislead

Fowler added another caution: early interactions may not be a true signal. About a year to a year and a half earlier, he tried Copilot-style completion. As an Emacs user ("the one true editor," he said), he set Emacs up to prompt and complete automatically. He used it for three or four days and gave up. Sometimes it produced something wonderful, but most of the time the output was garbage he deleted right away. If he had judged AI by that experience, he said, he would have "flipped the bozo switch" on it, as he did with blockchain.

He changed his mind because he kept probing. His most valuable discovery, he said, was Simon Willison's blog (Willison was speaking in the next room). His main takeaway was that using these tools well is a skill you have to learn. He saw a parallel with object orientation: people claimed to be doing objects in C++ or Java, but when you looked at their code they weren't using objects well. Fowler also described how he judges whom to trust. Does someone call everything wonderful, or do they acknowledge real problems and give a straight account? People who present both good and bad, and above all who will say "I don't know," are worth listening to. Besides Willison, he credited ThoughtWorks colleagues including Mike Mason and Birgitta Böckeler with showing him not to rely too much on his first reactions.

Beck said the answer can change week to week. He described trying something with Gemini that failed badly, then with Claude Code, which worked well for a while and then stopped working, then trying Gemini again on the same task and finding it now worked when it hadn't the week before. People want the answer, he said, but the answer keeps changing, so no one can have it in this environment. The bad news is that you can't have the answer. The good news is that nobody else has it either: "you're just as smart as everybody else because you're just as ignorant as everybody else."

Did Agile deliver "better, faster, cheaper"?

The host noted that the Agile Manifesto went up in 2001 with 17 names, Beck's first. Beck explained this was strictly alphabetical, and said it gives him endless joy. The host read the manifesto as promising four simple, relatable principles for building software better, faster, cheaper, and with higher quality. Companies adopting AI seem to expect much the same, so the host asked how Agile actually turned out.

Beck said: "it turns out that people don't want faster, cheaper, better." Inside companies, incentives are badly misaligned with those goals. Geeks who show up saying something is 40% better, 12% cheaper, and "less fattening" can be punished for it if it conflicts with incentives inside the organization. Ideally everyone would care about the same things, but that isn't how organizations work. Beck said this problem remains unsolved, so if AI promises the same benefits, he expects exactly the same reaction.

Similarities and differences between Agile and AI

Asked how AI's adoption might resemble Agile's much slower one, Fowler said the obvious difference is the sheer size and speed of AI's impact. He expects two similarities. First, there will be a large gap between people who use AI well and people who use it badly, and the key is working out how to use it well and putting in the effort to learn. Second, the ideas behind Agile and extreme programming were sound, yet "a huge snake oil industry" grew up around them, which he calls the "Agile industrial complex." He said the same is already happening with AI, and it is often hard to tell snake oil from the real thing, so you need to keep probing and stay wary.

AI as amplifier: juniors, experts, and the middle

Beck called AI an amplifier. For young people who learn quickly, it will, or at least can, amplify that. He said he personally thinks this is "the golden age of the junior programmer." People often tell him their child is in the second year of a CS degree and wants to switch to something "more commercial like art history." His response is an analogy: if you are a carpenter and the circular saw has just been introduced, carpentry isn't over and anyone still can't build a house. You simply have more powerful tools and spend less time on tedious work. In his view, fast-learning young people will learn faster, and effective experienced people will work faster and better.

His concern, which he said he picked up at the previous week's gathering, is the middle. After the dot-com crash, he said, a middle group who had come to programming for the money left, more or less for real estate. He doesn't know where today's middle will go, and he noted it is much larger than it was 25 years ago.

Fowler added that this middle has already been partly flushed out by industry retrenchments at the end of the zero-interest-rate period. The AI boom and the economic headwinds of the last two or three years are happening together, which he called an interesting mix. The 1990s dot-com era was different, he said, because it was "pretty much all solid boom."

"Get rid of the programmers," again

Beck noted that a recurring cycle feeds the current fear: every so often, someone announces that all the programmers can finally be eliminated. It started with COBOL, which was supposed to let business analysts write programs themselves. Agile was explicitly not that, he said. It aimed to make programmers more effective, and because programmers started it, they could push that agenda well. Now the "get rid of the programmers" story is back. Beck said programmers should ask themselves why people keep wanting to get rid of them. Some of the reasons have to do with programmers and some don't, but some do. He added that the recurring story also raises everyone's fear.

Fowler challenged the claim that "no one's going to write code in six months' time" by asking what "code" means. Even people who don't write code by hand are prompting and interacting with the genie, so what is that if not some form of code? He thinks the nature of code may become radically different, but people will still need to produce it and interact with it in some way.

What large enterprises are doing: confusion, panic, and security risk

The host said both speakers have their feet on the ground, unlike AI labs such as OpenAI, which must "talk their book," or others with a small incentive to sell tools. The host asked what they see in companies, including large, skeptical, traditional ones.

Fowler said "large-scale confusion and panic" is the norm across the board. Large enterprises have huge amounts of code and complex systems that fit together in ways that are hard to untangle. People ask whether these tools can handle a million lines of code, and Fowler noted that counts as a smaller codebase for many of those systems. The picture differs sharply from startups. An airline cannot accept the risk of going offline for a day or two.

He also raised other risks. He said he has met several groups, some at surprisingly large companies, who want to give an LLM full control of their email so it can read everything and answer most messages. Fowler and Beck both reacted on stage with an emphatic "NO." Fowler called the security risk "mind-boggling" and said he is very worried there will be some really bad security incidents this year because people aren't paying attention. He described a blind rush to grab attractive tools alongside real concerns.

The "re-soloing" of programming

Beck identified a major trend he called "the re-soloing of programming." A big part of extreme programming, he said, was creating a safe social environment for "basically antisocial people," and he stressed not just asocial but antisocial. On an XP team, people talk to each other for hours a day and are glad to, because the setup makes it a positive experience. Now he hears programmers say, "I've got six agents, so really I'm managing a team." Beck disagrees: you are using six tools at once, which is fine, but that is very different from talking with someone who believes slightly different things than you do, or whose energy level today differs from yours.

He compared this to the old days of individual offices, where you shut the door and pizza got slid underneath. That model was easy to manage and control. Then came a messy, social, complicated, chaotic process that "just happened to produce really good results," and management found it uncomfortable. He described the appeal of the new framing: instead of 50 people, a team of five who don't need to talk to each other, each running ten agents. His verdict: "It's not the same."

One-pizza teams or more capable two-pizza teams?

Fowler brought up a question from the previous week's discussion: will two-pizza teams shrink to one-pizza teams because agents don't eat pizza, or will two-pizza teams stay the same size and become far more effective? (Beck joked that you could build a genie that eats pizza.) Fowler said his bet is on more effective two-pizza teams.

He said they are starting to get interesting feedback about pair programming. Is the pair one human and a genie, or two humans with genies? With two humans, he suggested, you might control the genies somewhat better and keep the human interaction. He said he'd be very interested in reports from people trying pairs that direct genies, and possibly larger groups, such as mob programming combined with genies. He doesn't think one person with many genies is necessarily the right answer.

Beck said one person with many agents is the simplest framing to understand. His own experience pairing with two humans and one or more genies has been very positive, and he likes that the models are fairly slow. Each time a faster model comes out, he thinks there is less time to talk. You give a prompt and it goes off for three minutes, and meanwhile you can discuss your philosophy of naming, how to express conditionals, or what to do next. If it comes back in 15 seconds, there's no time for that conversation.

Advice for people who care about craft

The host closed by asking what engineers and engineering leaders who love the craft should do as they write less code themselves and lose some control.

Fowler cited a remark from the previous week, whose author he couldn't remember: the Venn diagram of developer experience and agent experience is a circle. What is good for agents is good for humans, and vice versa. He said he hears a lot of feedback that well-modularized code makes it easier for agents to work, and that good tests help agents as well as people. He again allowed that this might be wishful thinking because he wants it to be true, but said he will run with it for now. His advice was to keep focusing on craft and to work with the agent, teaching it and finding out how best to express that craft. As an example he described his colleague Unmesh Joshi, who, when working in a domain with an agent, tries to develop a precise language for talking about the domain. That is essentially the model-building, language-building work of domain-driven design, and Joshi finds it makes him more efficient in communicating with the agent. To Fowler, examples like this show a large overlap between what is good in existing practices and what will keep working with AI.

Beck's answer was more personal. He said he takes an "OCD enjoyment" in craft and needs to let go of it, because the satisfaction of getting one function exactly right no longer makes a difference. He said this "with sadness." He described what he loved: getting into the zone with a messy file, taking tiny safe steps without quite knowing where they lead, seeing a glimmer of the shape, and then having it suddenly pop into focus. "I can't do that anymore," he said. He can still build an overall understanding of what he's doing. His task now is to shift his enjoyment toward understanding the domain and how it connects to his program. For him, treating the program itself as the domain and making it better and better "just doesn't have leverage anymore."