Full-stack Next.js and AI developer, monthly retainer (UK hours)

We are a UK group of claims management and legal services businesses. We are building our own software in-house: a claims management system, a sales platform, and a set of AI assistants that help our staff and talk to clients by SMS and WhatsApp. The project is well under way. Every platform is already planned, the plans are written down, and much of the build is done. Most of the code has been written with AI. I am working on it myself, but I do not have the time to finish it alone, so I need an experienced developer to help me get it finished as soon as possible. What you will do - Check, test and improve everything that has been built, and add the features still to come - Find and fix bugs and errors before they reach our staff and clients - Bring your own knowledge and experience to make the system robust, secure and reliable, and tell us where it could be done better How the applications are built - Next.js 15 and React applications in TypeScript - Postgres databases - AI agents on the Claude and OpenAI APIs: tool calling, structured output, and prompts kept in the database - Microsoft Power Apps and Dataverse for one version of the claims system - Our own Linux server (VPS), with Docker, Caddy and Cloudflare - Integrations with WhatsApp, DocuSign and our CRM What we need from you - Strong, recent Next.js, React and TypeScript work that you can show us - Solid Postgres: table design, migrations and row-level security - AI features you have put live on the Claude or OpenAI APIs, not only prototypes - Experience with Microsoft Power Apps and Dataverse - Confidence on a Linux server: Docker, a web server, logs and deployments - A careful approach to testing and code review, and good git habits - Happy to review and extend code written with AI - At least four hours a day overlapping with UK office hours (9am to 5.30pm UK time) - Clear written English Nice to have - Windmill, or a similar job runner such as Temporal or Airflow - Playwright and Sentry How we work - A fixed retainer of 60 hours a month - The first term is two months, then it rolls on month by month - You sign an NDA and a data processing agreement before you get any access. We handle personal data under UK GDPR. - You get your own logins, with only the access each piece of work needs - Work is agreed in writing, and every change comes with a short note of what changed and how it was tested To apply Start your proposal with the word "Retainer" so we know you have read this post. Tell us about one AI feature you built that is live today, and send links to Next.js and Postgres work we can look at.