Senior Full-Stack Engineer to build AI Products for a Live Multi-Tenant SaaS platform

We run an established B2B SaaS with paying customers on a live multi-tenant platform. AI is already part of the product, we've shipped an AI assistant and RAG-powered search and now we're looking for a senior engineer to help build the next generation of AI capabilities. I'm looking for someone who can own AI features from end to end. That means understanding the user problem, designing the experience, building the frontend, implementing the backend, integrating the model, testing everything properly, and shipping production-ready code. You'll be joining an existing product, not starting from scratch. The infrastructure, architecture, and engineering patterns are already in place. Here's what's next on our roadmap: An AI-powered onboarding flow that configures a new workspace from a plain-English description of the customer's business. Inline AI actions across existing forms to rewrite, summarize, extract, and classify content while users are working. An AI insights page that sits on top of our analytics data and turns it into clear, actionable narratives. What I'm Looking For I'm looking for the kind of engineer who can take a one-paragraph feature brief and come back with a clean, production-ready pull request after asking the right questions. You care about how AI actually feels inside a product. You know when to stream responses instead of showing spinners, when optimistic updates make sense, and how to handle failures without breaking the user experience. You write code that's clean, maintainable, and easy for the rest of the team to build on long after the contract ends. You Should Be Comfortable With Next.js, React, and TypeScript at a senior level, including complex state management and streaming UI. Node.js and Python for backend development. Claude API and OpenAI API, including prompting, tool calling, structured outputs, and streaming. PostgreSQL and working confidently inside a mature multi-tenant codebase you didn't build. Owning features end to end with minimal supervision, communicating early when you hit blockers instead of disappearing. How to Apply Please skip the generic copy-paste proposal—I can spot those immediately. Start your proposal with the word "Spider" so I know you actually read the job description.