AI Product Engineer

Pantalent; London; Hybrid; GBP 40,000 - 70,000; Full time

Job summary

A stealth-mode AI SaaS startup is seeking a Founding Product Engineer. This role involves building AI-driven solutions for finance teams, integrating LLMs into a core platform, and shaping product development. Ideal candidates will have a strong full-stack background and a passion for innovative AI solutions.

Benefits

Competitive salary + early-stage equity

Hybrid working (3 days in-office)

Huge ownership and rapid shipping

Qualifications

• Passionate about building products and working with LLMs.
• 0-3 years of relevant experience.
• Comfortable coding and product thinking.

Responsibilities

• Implementing and productising LLMs and agentic systems.
• Building and deploying LLM-powered agents.
• Collaborating closely with founders.

Skills

Experience across the full-stack (Typescript, React, Vue, Node)

Experience with LLMs (OpenAI, Claude, etc.)

Strong understanding of AI agents

Ability to work in fast-paced environments

Tools

LangChain

Vector databases

RAG pipelines

Job description

The Opportunity
We’re working with a stealth-mode agentic conversational AI SaaS startup that’s on a mission to automate the accounts receivable (AR) process for finance teams. Today, AR team members spend most of their time in a shared email inbox responding to customers’ billing questions, or manually chasing customers that haven’t paid. AI agents can do this better.

The company is backed by a £3 million in funding from top tier global VC investors and is founded by entrepreneurs that have previously scaled a YC startup from 0-$20 million in revenue.

They're now hiring a Founding Product Engineer with expertise in LLMs and agent-based systems. This is a rare opportunity to get in early at a highly ambitious AI-native startup, working directly on productionising models and shaping the product from the ground up.

This is an exciting opportunity for someone with 0–3 years of experience who’s passionate about building products and thrives in fast-paced environments. Please note: this is not a Data Science or Machine Learning role. You'll be working across the full stack, contributing to real product development from day one.

What You’ll Be Doing
This role blends applied AI with full-stack product development and is principally responsible for implementing and productising LLMs and agentic systems:

• Building and deploying LLM-powered agents to handle complex business logic, workflows, and customer interactions.

• Integrating AI systems directly into the core SaaS platform to deliver intelligent automation at scale.

• Collaborating closely with the founders define features, ship fast, and iterate based on user feedback.

• Taking models from prototype to production, including fine-tuning, evals, and monitoring.

• Writing clean, scalable code across the stack (TypeScript/React/Node), with a strong bias toward shipping impactful features.

• Staying up to date on the latest in the LLM ecosystem and bringing best practices into the engineering culture.

What They’re Looking For
This role is ideal for someone who’s as comfortable coding as they are thinking about a product, someone who thrives in ambiguity and has a genuine passion for working with LLMs and agentic systems. You’ll have:

• Experience across the full-stack (Typescript, React, Vue, Node).

• Genuine interest in and experience with working with LLMs (OpenAI, Claude, etc.)

• Strong understanding of AI agents and how to design systems that make autonomous decisions.

• Comfortable working in fast-paced, early-stage environments with lots of ownership.

• AI-native mindset. You understand how to weave intelligence into products from the ground up.

Bonus Points For:

• Experience building SaaS platforms, especially in Fintech.

• Background in autonomous systems, workflow automation, or AI-driven decision engines.

• Experience with tools like LangChain, semantic search, vector databases, or RAG pipelines.
  

Why Join?

• Be part of the founding team of a well-funded, high-potential startup.

• Work on problems that are messy, complex, and hugely valuable

• Competitive salary + early-stage equity.

• Hybrid working (3 days in-office in London).

• Huge ownership, rapid shipping, and a strong culture of innovation.