Founding Full-Stack Engineer London, UK • In office

Zalos Limited; Greater London; Hybrid; GBP 70,000 - 90,000; Full time

Job summary

Zalos Limited is seeking a Founding Full-Stack Engineer to own the development of a transformative enterprise software solution. You will be responsible for building the product experience that simplifies complex workflows into actionable outcomes, integrating AI into the core of the application.

The role requires deep experience with LLM APIs and a hands-on approach to reliability and user-centric design. Join us to innovate how enterprises operate and work directly with founders from day one.

Qualifications

• Experience shipping AI-powered features in production.
• Hands-on experience with LLM APIs and agentic patterns.
• Focus on reliability, latency, and cost in engineering.

Responsibilities

• Design and own core agent architecture for intent processing.
• Build reliable LLM pipelines with enterprise data.
• Work with founders to understand AI failures and improve systems.

Skills

AI-powered feature delivery

LLM APIs

Reliability engineering

Browser automation

Pragmatism in startup environments

Job description

About the role

As Zalos's Founding Full-Stack Engineer, your job is to build the product experience that makes this real. You'll be designing and shipping the application surfaces, backend services, and workflow infrastructure that turn messy enterprise work into correct, auditable action across systems of record. This is a hard, important part of the product. It's entirely yours to own.

What we’re building

Enterprise software was built to store data and enforce process. It was never built to be used by humans who have better things to do. The result: highly trained people wasting hours every day fighting screens instead of doing the actual work.

• Intent-to-action: A user describes an outcome. Zalos figures out which systems to touch, in which order, with which data, and executes it with the right approvals and a clean audit trail.
• Cross-system workflows: Event-driven chains that span SAP, Salesforce, and ServiceNow simultaneously.
• Computer-use for the long tail: Not every enterprise workflow has a reliable API. We use computer-use agents to automate the 30 to 40 percent of processes that live in screens, VDI sessions, and legacy thick clients.

What you'll work on

• Design and own the core agent architecture: how we take a natural language intent, decompose it into steps, call the right APIs and UI agents, handle failures gracefully, and close the loop with the user
• Build reliable, production-grade LLM pipelines covering context management, tool use, structured outputs, and multi-step reasoning across systems with real enterprise data
• Work directly with the founders and customers to understand where AI fails in real enterprise workflows and translate that into better systems
• Set the technical standards for how we build AI at Zalos

Must haves

• You’ve shipped AI-powered features that real users depend on in production. You know what breaks and how to prevent it.
• Deep hands‑on experience with LLM APIs, agentic patterns, and tool/function calling.
• You think about reliability, latency, and cost as first‑class engineering concerns, not afterthoughts.
• You build tests/evals before you ship, not after something breaks in front of a customer.
• High ownership: you take something from an ambiguous problem statement to a clean, working solution with minimal hand‑holding.
• You’re pragmatic. Startups are always on fire somewhere. You know when to let something burn and when to drop everything.

Nice to haves

• Computer-use or browser automation work with tools like Playwright, browser agents, or UI parsing.
• Fine‑tuning or RLHF on domain‑specific tasks.
• Prior founding engineer or early‑stage startup experience.

The team you’ll work with

You’ll work directly with the founders from day one. No engineering manager in the way, no sprint planning theatre.