Contract Full-Stack JavaScript Developer (AI Platform) Location: 3 days per week in London Office Duration: 4 weeks with a longer term extension afterwards. IR35 Status: Outside IR35 Rate: £500p/d – £600p/dOpus is partnering with a cutting-edge FinTech start-up to secure a Contract Full-Stack JavaScript Developer.You’ll be joining a small, high-calibre team building a platform to improve workflows within the the FinTech space. They have a genuinely interesting problem at the intersection of frontend engineering, backend systems, and applied LLM tooling.This is a true 0–1 build, ideal if you enjoy ownership, clean abstractions, and shipping product quickly. What You’ll Be Working On

• Building and extending agent-driven workflows.
• Developing context management and LLM entry points. Only application-layer LLM integrations, not model training)
• Expanding slide generation functions and data structures.
• Full-stack feature development, with a frontend-heavy bias
• Collaborating closely with product and engineering stakeholders in a fast-moving environment

Tech Stack

• Next.js
• TypeScript
• Tailwind CSS
• Node.js
• PostgreSQL
• Claude Agent SDK
• Pydantic
• AWS
• Terraform
• Modal Sandboxes

Interested?Apply now or send your latest CV to ASAP!If you haven’t heard back within 48 hours, please assume your application was not successful this time.