Martin Fowler

JUNE 18, 2025

As computer systems get more sophisticated we've seen a growing trend to value deep specialists. But we've found that our most effective colleagues have a skill that comes from spanning many specialties. We are thus starting to explicitly recognize this as a first-class skill of “Expert Generalist” This is the first installment of an article detailing how we think about this skill, starting with the first three characteristics of an Expert Generalist.

Trends 276

Trends System 276

Martin Fowler

JUNE 4, 2025

In the past few weeks, multiple “autonomous background coding agents” have been released. Birgitta Böckeler tried out giving a task to OpenAI Codex to see what she could learn. Here she describes one particular Codex run, to help us look behind the scenes, and make some observations about its contribution to our work.

Examples 181

Examples 181

Martin Fowler

JUNE 3, 2025

I set up Google Analytics on my site in 2010, and since then use it to track page views to my site. I only care about page views, which I find useful to figure out which pages get the most traffic. Its interesting data, and sometimes rather useful. But Google collects much more information than just page views, and its tracking is more intrusive than I would like.

Analytics 122

Analytics Open Source Report Data 122

Martin Fowler

MAY 28, 2025

Here's one of the best tips I know for writers, which was told to me by Bruce Eckel. One you've got a reasonable draft, read it out loud. By doing this you'll find bits that don't sound right, and need to fix. Interestingly, you don't actually have to vocalize (thus making a noise) but your lips have to move. 1 This advice is for those who, like me, strive to get a conversational tone to their writings.

Course 187

Course Company 187

Martin Fowler

MAY 6, 2025

While LLMs excel at generating cogent text based on their training data, they may also need to interact with external systems. Kiran Prakash describes how we get them to construct external function calls to do this. The LLM does not execute these calls directly, instead it creates a data structure that describes the call, passing that to a separate program for execution and further processing.

Artificial Inteligence 307

Artificial Inteligence Construction Training Programming 307

Martin Fowler

APRIL 30, 2025

Creating a user interface that visualizes a real-world structure — like the Thirty Meter Telescope's mirror — might seem like a task that demands deep knowledge of geometry, D3.js, and SVG graphics. But with a Large Language Model (LLM) like Claude or ChatGPT, you don't need to know everything upfront. Unmesh Joshi describes how working with an LLM gave him a working prototype even when he's unfamiliar with the underlying tech.

Artificial Inteligence 221

Artificial Inteligence ChatGPT 221

Martin Fowler

APRIL 17, 2025

AI editors like Cursor can generate code with remarkable speed using LLMs, handling boilerplate and providing functional snippets for various tasks. However, when building robust systems, functional correctness is only the starting point. Code must also be safe, predictable, maintainable, and free from subtle side effects. Unmesh Joshi demonstrates, through a dialogue between a developer and an LLM , how expert guidance is crucial to transform an initial, potentially unsafe code snippet into a r

Artificial Inteligence 242

Artificial Inteligence System Development 242

Martin Fowler

APRIL 3, 2025

A few years ago, whenever I published a new article here, I would just announce it on Twitter, but since the Muskover its importance has declined, and now I post updates to several services. To compare engagement on these services, I've looked at reposts, likes, and replies to two dozen of my recent posts.

Media 171

Media Social 171

Martin Fowler

APRIL 1, 2025

I've always enjoyed reading, and for most of my life I've particularly enjoyed reading history. I've head many great things about Robert Caro's books, but was deterred by their size. Finally, with his first book newly available as an ebook, I decided to dip my toes in. The books are too good for me to escape.

eBook 172

eBook 172

Martin Fowler

MARCH 25, 2025

As agentic coding assistants get more capable, Birgitta Böckeler is trying them to change existing codebases. This has led to some impressive collaboration sessions, but she's needed to intervene, correct and steer all the time. In her latest post , she describes examples of these interventions, giving ideas of the types of skills we currently need to correct the tools' missteps.

Development 245

Development Examples Tools 245

Martin Fowler

FEBRUARY 25, 2025

While RAG is the most common way to focus a foundation model on material outside its training set, Bharani Subramaniam and I now finish our current batch of patterns by examining our experience with Fine Tuning where we learned to prioritize curating high-quality data.

Training 189

Training Data 189

Martin Fowler

FEBRUARY 18, 2025

Gen AI systems are gullible, and can easily be tricked into responding in ways that are contrary to an enterprise's policies or leak confidential information. Bharani Subramaniam and I describe how we can counter this by adding guardrails at the boundaries of the request/response flow. We also conclude our discussion of RAG with an overview of how all the RAG component patterns fit together.

Policies 189

Policies Enterprise System 189

Martin Fowler

FEBRUARY 17, 2025

Recent LLM models have provided reasoning capabilities. Birgitta Böckeler asks what role these play with coding tasks. She doesn't have an answer, but does have questions and thoughts - and has not found such capabilities worthwhile so far.

Artificial Inteligence 187

Artificial Inteligence Software 187

Martin Fowler

FEBRUARY 13, 2025

LLMs struggle with large amounts of context. Bharani Subramaniam and I explain how to mitigate this common RAG problem with a Reranker which takes the document fragments from the retriever, and ranks them according to their usefulness.

How To 189

How To 189

Martin Fowler

FEBRUARY 11, 2025

Users often have difficulty writing the most effective queries. Bharani Subramaniam and I explain Query Rewriting : getting an LLM to formulate alternative queries to send to a RAG's retriever.

Artificial Inteligence 189

Artificial Inteligence 189

Martin Fowler

FEBRUARY 5, 2025

Today Bharani Subramaniam and I outline four limitations to the simple RAG from yesterday, and the pattern that addresses the first of these: Hybrid Retriever. This tackles the inefficiencies of embeddings-based search by combining it with other search techniques.

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Martin Fowler

FEBRUARY 4, 2025

was on a panel at goto Copenhagen last September with Holly Cummings, Trisha Gee, Dave Farley, and Daniel Terhorst-North. We discussed the current state of software development and where it was heading. Given the timing, there was much discussion about the role AI would play in our profession's future.

Development 282

Development Software Development Software 282

Martin Fowler

FEBRUARY 4, 2025

A pre-trained GenAI model lacks recent and specific information about a domain. Bharani Subramaniam and I explain how Retrieval Augmented Generation (RAG) can fill that gap.

Training 245

Training 245

Martin Fowler

JANUARY 29, 2025

GenAI systems, like many modern AI approaches, have to handle vast quantities of data, and find similarities between elements in an image or chunk of words.

Tools 180

Tools System Data 180

Martin Fowler

JANUARY 24, 2025

Luca Rossi hosts a podcast (and newsletter) called Refactoring, so it's obvious that we have some interests in common. The tile comes from me leaning heavily on Beth Anders-Beck and Kent Beck's metaphor of The Forest and The Desert. We talk about the impact of AI on software development, the metaphor of technical debt, and the current state of agile software development.

Software Development 246

Software Development Agile Software Development 246

Martin Fowler

JANUARY 22, 2025

Juntao Qiu finishes his description of codemods by looking at some other approaches outside the JavaScript world such as JavaParser and OpenRewrite.

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Martin Fowler

JANUARY 15, 2025

So far the codemods that Juntao Qiu has described are fascinating, but rather straightforward. Real codebases offer more challenges. In this installment , he goes into how to tackle more complicated cases by composing codemods.

How To 241

How To 241

Martin Fowler

JANUARY 9, 2025

I've got into the habit of starting the New Year by sharing six favorite albums I discovered during the last year. This years set includes Celtic jazz, trip-hop neo-fado, jazz-fusion for the 2020's, playful harmonies, and a vibrant collaboration between Indian classical musicians and a string quartet. (I was also unable to limit myself to six.

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Martin Fowler

JANUARY 8, 2025

Juntao Qiu moves onto a more complex example of a codemod , one that extracts a tooltip responsibility from a JSX component. This illustrates how to manipulate the AST in several steps.

Examples 182

Examples How To 182

Martin Fowler

JANUARY 7, 2025

As a library developer, you may create a popular utility that hundreds of thousands of developers rely on daily, such as lodash or React. Over time, usage patterns might emerge that go beyond your initial design. When this happens, you may need to extend an API by adding parameters or modifying function signatures to fix edge cases. The challenge lies in rolling out these breaking changes without disrupting your users’ workflows.

Tools 301

Tools Development 301

Martin Fowler

DECEMBER 12, 2024

Design tokens are fundamental design decisions represented as data. Andreas Kutschmann explains how they work and how to organize them to balance scalability, maintainability and developer experience.

Architecture 212

Architecture Scalability Organization Data 212

Martin Fowler

DECEMBER 10, 2024

Once we've designed our initial data products, Kiran Prakash finishes his article by leading us through the next steps : identifying common patterns, improving the developer experience, and handling governance.

Data 189

Data Government Development 189

Martin Fowler

DECEMBER 4, 2024

Having got an initial data product, Kiran Prakash leads us through the next steps: covering similar uses cases to generalize the data product, determining which domains the products fit into, and considering service level objectives.

Data 189

Data 189

Martin Fowler

DECEMBER 3, 2024

Increasingly the industry is seeing the value of creating data products as a core organizing principle for analytic data. Kiran Prakash has helped many clients design their data products, and shares what he's learned. In particular his methodical approach doesn't begin by thinking about some data that might be handy to share, but instead works from what consumers of a data product need.

Data 269

Data Analytics Industry Organization 269

Martin Fowler

NOVEMBER 19, 2024

A very powerful new coding assistance feature made its way into GitHub Copilot at the end of October. This new “multi-file editing” capability expands the scope of AI assistance from small, localized suggestions to larger implementations across multiple files. Birgitta Böckeler tries out this new capability and finds out how useful its changes tend to be, and wonders about what feedback loops are needed with them.

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Martin Fowler

NOVEMBER 13, 2024

With the recent uptick in tech activity on Bluesky, I've decided that I will start posting there in addition to my current locations. I've also put together my general thoughts on the state of social media, and how I'm using it, now that it's two years since The Muskover.

Media 206

Media Social 206

Martin Fowler

NOVEMBER 5, 2024

Matthew Foster and John Mikel Amiel Regida finish their account of how they incrementally modernized a mobile application by looking at the results of their work. They achieved a significant shortening of time to new value, and found that changes in the new application could be prepared in about half the time it took on the old codebase.

Mobile 175

Mobile Applications 175

Martin Fowler

OCTOBER 30, 2024

Matthew Foster and John Mikel Amiel Regida dive into the details of incrementally modernizing a legacy mobile application. They look a t how to implant the strangler fig into the existing app, setting up bi-directional communication between the new app and the legacy, and ensuring effective regression testing on the overall system.

Mobile 174

Mobile Testing Applications System 174

Martin Fowler

OCTOBER 29, 2024

My colleagues are often involved in modernizing legacy systems, and our approach is to do this in an incremental fashion. Doing this with a mobile application raises some specific challenges. Matthew Foster and John Mikel Amiel Regida share their experiences of a recent engagement to do this, shifting from a monolithic legacy application to one using a modular micro-app architecture.

Mobile 316

Mobile Fashion Architecture Applications 316

Martin Fowler

OCTOBER 4, 2024

I was interviewed on the Book Overflow podcast about the Refactoring book. We talked about the origins of the book, the relationship between refactoring, testing, and extreme programming, how refactoring is used in the wild, and the role of books and long-form prose today.

Programming 269

Programming Testing 269

Martin Fowler

SEPTEMBER 18, 2024

Alessio Ferri , Tom Coggrave , and Shodhan Sheth use their combination of an AST-fueled knowledge graph and LLMs to gain understanding of legacy systems. They have found it aids them both in extracting the low-level details of the code and can provide high-level explanations to support human-centered approaches such as event storming.

System 246

System 246

Martin Fowler

SEPTEMBER 17, 2024

Most of the talk about the impact of GenAI on software development is about its ability to write (messy) code. But many of us think it's going to be much more useful to help us understand existing messy code, as part of a modernization effort. My colleagues Alessio Ferri , Tom Coggrave , and Shodhan Sheth have been considering how GenAI can do this , including building an internal tool to help explore the possibilities.

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Meeting Artificial Inteligence Software Development Tools 349