Full-stack contractor for the hard parts of SaaS: payments/billing and AI agents in production. Remote, UTC+1https://jguillaumesio.com/https://jguillaumesio.com/blog/ai-branch-diff-summary/https://jguillaumesio.com/blog/ai-branch-diff-summary/How to generate a smart summary of branch diffs. Highlights deleted files and renames to give AI agents the context they need to review, refactor, or document code.Tue, 28 Apr 2026 00:00:00 GMTdevtoolsaihttps://jguillaumesio.com/blog/ai-generated-infrastructure-problems/https://jguillaumesio.com/blog/ai-generated-infrastructure-problems/I asked AI to generate Terraform for a standard AWS setup. It produced 2,400 lines that worked perfectly. Here's why I'd never deploy it to production.Tue, 14 Apr 2026 00:00:00 GMTdevopsarchitectureaihttps://jguillaumesio.com/blog/architecture-more-important-than-code/https://jguillaumesio.com/blog/architecture-more-important-than-code/I spent 2 weeks making my serverless functions clean. The architecture was wrong. I rewrote everything as a single Express server and it was simpler.Tue, 02 Jun 2026 00:00:00 GMTarchitecturedevopshttps://jguillaumesio.com/blog/checking-ai-context-window/https://jguillaumesio.com/blog/checking-ai-context-window/How to verify the actual context window of an LLM, understand external vs internal context, and avoid the silent truncation problem.Tue, 07 Apr 2026 00:00:00 GMTaihttps://jguillaumesio.com/blog/debugging-infrastructure/https://jguillaumesio.com/blog/debugging-infrastructure/My blog returned 404 on every page at 2 AM. I had zero visibility into why. Here is the debugging infrastructure I wish I had set up from day one.Tue, 26 May 2026 00:00:00 GMTdevopsarchitecturehttps://jguillaumesio.com/blog/perfect-code-less-maintainable/https://jguillaumesio.com/blog/perfect-code-less-maintainable/I spent 3 hours reviewing a 200-line PR that handled every edge case. A 40-line version with a TODO would have been better. Here's why perfect code slows you down.Tue, 19 May 2026 00:00:00 GMTarchitecturewebdevhttps://jguillaumesio.com/blog/social-media-previews-react/https://jguillaumesio.com/blog/social-media-previews-react/How to handle Open Graph meta tags for LinkedIn, Google, and Discord previews in a React SPA using server-side user-agent detection with nginx or .htaccess.Tue, 05 May 2026 00:00:00 GMTwebdevreacthttps://jguillaumesio.com/blog/stripe-alternatives-eu/https://jguillaumesio.com/blog/stripe-alternatives-eu/Stripe is the default answer for online payments. But if you only need one payment method, you're paying for features you'll never use. Here's what I found when I actually compared providers.Tue, 12 May 2026 00:00:00 GMTwebdevarchitecturehttps://jguillaumesio.com/blog/testing-lambda-eventbridge-locally/https://jguillaumesio.com/blog/testing-lambda-eventbridge-locally/How to test AWS Lambda functions and EventBridge rules locally using SAM, LocalStack, and docker-compose. No cloud deployment needed.Tue, 21 Apr 2026 00:00:00 GMTdevopsawshttps://jguillaumesio.com/blog/token-economy-loom-memory/https://jguillaumesio.com/blog/token-economy-loom-memory/How loom-memory turns a Git repository into a persistent knowledge base for AI agents. Reduce token spend by giving models durable context instead of cold reads.Tue, 31 Mar 2026 00:00:00 GMTaidevtoolshttps://jguillaumesio.com/blog/welcome/https://jguillaumesio.com/blog/welcome/Hi, I'm jguillaumesio, a full-stack contractor based in Paris, working 100% remote. I help SaaS teams ship the parts they can't afford to get wrong: payments/billing integration and AI agents in production. This blog is where I write about what I ship.Wed, 27 May 2026 00:00:00 GMTintro