Lead Machine Learning Engineer

Harnham; San Francisco (CA); On-site; USD 180,000 - 240,000; Full time

Job summary

Harnham is partnering with a well-funded early-stage startup to redefine how designers build in the AI era. We seek an AI systems lead to define and scale AI across the product, integrating models, systems, and product in a fast-paced environment.

You’ll own AI architecture, build production-grade LLM features, and design multi-step tool workflows, collaborating with product, design, and engineering to deliver high-impact AI capabilities.

Qualifications

• 5+ years of software engineering experience.
• 2+ years working with LLM APIs and prompt engineering in production.
• Strong proficiency in TypeScript or Node.js and Python.
• Experience with LLM evaluation, benchmarking, and performance measurement.
• Hands-on experience with fine-tuning (LoRA, full fine-tuning, distillation).
• Experience building agent-based AI systems.
• Ability to own systems end-to-end in a fast-paced environment.

Responsibilities

• Own AI architecture and technical direction across the product.
• Build and ship production-grade LLM features with clear quality and performance metrics.
• Design and optimize AI pipelines across prompting, retrieval, agents, and evaluation.
• Lead development of agentic systems and multi-step tool use workflows.
• Establish standards for model evaluation, benchmarking, and observability.
• Partner closely with product, design, and engineering to ship high-impact AI features.

Skills

Software engineering

LLM APIs

Prompt engineering

TypeScript

Node.js

Python

LLM evaluation

Fine-tuning

Agent-based AI systems

Tools

TypeScript

Node.js

Python

Job description

We’re partnered with a well-funded early-stage startup rethinking how designers build in the AI era, backed by top-tier investors and operators from leading AI and technology companies. They’re building a next-generation design platform powered by LLMs, focused on helping product teams move from idea to production faster through intelligent, AI-driven workflows.

This is a foundational, high-ownership role where you’ll define and scale AI systems across the product. You’ll operate at the intersection of models, systems, and product, turning cutting-edge AI capabilities into reliable, measurable user-facing features.

What You’ll Do

• Own AI architecture and technical direction across the product
• Build and ship production-grade LLM features with clear quality and performance metrics
• Design and optimize AI pipelines across prompting, retrieval, agents, and evaluation
• Lead development of agentic systems and multi-step tool use workflows
• Establish standards for model evaluation, benchmarking, and observability
• Partner closely with product, design, and engineering to ship high-impact AI features

Requirements

• 5+ years of software engineering experience
• 2+ years working with LLM APIs and prompt engineering in production
• Strong proficiency in TypeScript or Node.js and Python
• Experience with LLM evaluation, benchmarking, and performance measurement
• Hands-on experience with fine-tuning (LoRA, full fine-tuning, distillation)
• Experience building agent-based AI systems
• Ability to own systems end-to-end in a fast-paced environment

What You’ll Build

• Custom smaller models tailored to specific design workflows
• Multi-step AI agent systems with tool use
• Real-time, streaming AI experiences
• Context-aware code generation and intelligent suggestions

If you're interested in building AI-native products that directly shape how modern teams design and build software, this is a rare chance to have early, meaningful impact on both the product and technical direction.