Problems hit while building React, Next.js and AI-agent projects, and the working solutions that came out of them - written up by Kartik Saxena as full case studies with the actual code.
Migrating from Vite to Next.js renamed every VITE_ env var to NEXT_PUBLIC_. The host still had the old names, so Firebase initialised with undefined keys, getAuth() threw at module scope, and because that module was imported by every page the ErrorBoundary replaced the whole site with 'Something went wrong'.
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Adding an MDX blog to a Next.js 16 site on Turbopack fails twice: the build rejects remark and rehype plugins passed as imported functions, and a root-level mdx-components.js silently loses every Tailwind class in production.
Read the write-up →Search Console reported 'Crawled - currently not indexed' with no referring sitemaps and no referring page, while robots.txt, canonicals and the sitemap were all verifiably correct.
Read the write-up →Every post here is a problem I hit on real client or product work, written up with the code that fixed it. More about Kartik.