Sebastien Castiel | Articles

There has been a Spliit app on the App Store since the end of 2024.

One of the first things people notice about Spliit is what’s not there.

Until now, if you wanted to support Spliit financially, you had two options: GitHub Sponsors, or a direct donation through a Stripe link.

$ git log --oneline gama/runtime - LangChain (TypeScript) Dec 2024 - LangGraph (Python) mid 2025 - Google ADK + Agent Engine (Python) Oct 2025 - Mastra (TypeScript) Mar 2026 + Claude Agent SDK (TypeSc…

It’s been three months since I last wrote a line of code.

I know that feedback about using AI as a dev is so mid-2025, but I feel there are still some things to say.

Most leverage from AI doesn’t come from writing AI code—it comes from writing code that AI can use.

Revenue operations teams face a constant challenge: complex workflows that require deep domain knowledge, even for seemingly simple tasks.

Seven hours on a plane, zero internet, and a curiosity about local AI coding.

Developers on my team use Cursor’s Tab feature.

When I first started using Claude Code, I had a naive approach to working with it.

For the first time in my career, I have absolutely no idea what the software engineer job will look like in five or ten years.

I created Spliit a few years ago, but the version you can use today is only one year old.

When I first built Spliit, I naturally chose English as the default language to reach the widest audience possible.

Splitwise was created in 2012 as a free application to split expenses between friends.

When I created Spliit, I wanted it to be minimalist and not implement dozens of features that nobody uses.

In many years of writing and reviewing code, I learned a few secrets to craft better pull requests and review code more efficiently.

Server Actions are a new feature in Next.js.

React is living something these days.

“The code must be reviewed by senior developers.”

A recurring question I hear from people learning React: “how do I know if I’m ready to apply to junior React developer jobs?”.

I’ve always loved sharing my knowledge.

I remember the time it was so cool to have a view counter on my personal website.

If you have ever created an API or a form accepting user input, you know what data validation is, and how tedious it can be.

If you sell some products on Gumroad and also have a personal website, maybe you’d like to automatically list your products on this website.

A few months ago, I rebuilt my blog using Next.js, writing my posts with Markdown.

At the same time I released the new design for this blog using Next.js, Vercel announced a new library to generate OpenGraph (OG) images.

I discovered Kotlin recently and realized that, for many people, it was only a new syntax for Java.

Ada is a developer.

I released my course about React hooks a while ago.

In the past four years, I wrote three eBooks about programming.

Redux is an awesome library to handle the state of big applications, React or not.

React hooks are awesome, but they are not as easy to use as they sound.

Although I love React and am more used to single-page applications (SPA), I decided to leave them aside the time of a side project and to use plain old Node.js, Express, Pug, and MongoDB.

As a developer, you may have acquired some skills that you don’t find the time to practice.

A couple of days ago, I created a 3D version for a book I was writing, with CSS only.

Think about a normal day of work.

When you’ve been working as a developer for several years, improving at coding is not enough to become better at your job.

It’s been some time that I hear about Flutter, the UI library by Google supposed to be a concurrent for React.

Thanks to a recent evolution in mobile and desktop operating systems, it is more and more common for users to expect two UI themes for apps and websites: a light one and a dark one.

This blog has been using Gastby for a year now.

Have you ever dreamed to wake up one morning and realize you felt different, more powerful?

I’ve been living in Montréal for almost two years now.

You can use everyday a library such as React, Redux or Redux-Saga.

This article is not recent, but still relevant!

Big week for me: I finished writing my eBook in French about React, and I couldn’t be prouder.

Note du 5 nov. 2020: cet article date un peu maintenant, mais son propos me semble toujours valide.

Voilà quelques mois, j’étais à la recherche d’un nouveau projet personnel.

Not that long ago I used Create-React-App a lot to quickly boostrap my React projects.

Writing reusable components in React is something every React developer care about (or should care about).