Contract Full-Stack JavaScript Developer - AI Platform

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/d

Opus 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 FinTech space. They have a genuinely interesting problem at the intersection of Front End engineering, Back End 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 Front End-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 (see below) ASAP!
If you haven't heard back within 48 hours, please assume your application was not successful this time.