Senior Software Engineer (AI Agents)
ArcadiaAbout the role
A high-growth startup is building the infrastructure to measure how LLMs actually perceive and process data, giving teams visibility into model behavior that's historically been a black box. They're looking for a Senior Software Engineer to join their founding team. This is a 0→1 opportunity to architect the core product alongside a small, technical founding team. You'll move fluidly between frontend, backend, and applied AI work, including building and orchestrating AI agents end-to-end, with high ownership in a fast-paced, autonomous environment.
This is an onsite role in San Francisco, CA.
What you'll do
Own full stack architecture decisions from day one, spanning TypeScript/React on the frontend and Python on the backend
Design and build systems that evaluate and quantify LLM perception of structured and unstructured data
Build and orchestrate agentic workflows for automated evaluation, data processing, and model behavior analysis
Work directly with LLMs and model outputs to build novel measurement and evaluation frameworks
Ship product end to end, from data pipelines to user-facing interfaces
Set technical standards and engineering culture as one of the first hires
What we're looking for
Strong full stack experience with TypeScript, React, and Python in production environments
Hands-on experience building with or around LLMs, whether that's evals, fine-tuning, RAG, or applied AI product work
Founding engineer, Founder, or very early startup experience, comfortable with ambiguity and fast iteration (must have)
Bias toward shipping over perfecting, balanced with genuine technical depth
Excitement about being deeply hands-on at every layer of the stack
Why this role
You'd be one of the first engineering hires at a high growth, well-backed startup tackling a problem that's becoming increasingly critical as LLMs get embedded everywhere. Huge ownership, huge technical surface area, and a seat at the table for foundational product decisions
Responsibilities
- Own full stack architecture decisions from day one
- Design and build systems that evaluate and quantify LLM perception
- Build and orchestrate agentic workflows for automated evaluation
- Work directly with LLMs to build measurement and evaluation frameworks
- Ship product end to end, from data pipelines to user-facing interfaces
- Set technical standards and engineering culture
Qualifications
- Strong full stack experience with TypeScript, React, and Python
- Hands-on experience building with or around LLMs
- Founding engineer or early startup experience
- Bias toward shipping over perfecting
- Excitement about being deeply hands-on at every layer of the stack
Skills mentioned
About Arcadia
Arcadia is a high-performance recruitment firm operating on a top percentile trajectory across North America, with growth speed and per-head productivity placing it among the top 1–3% of agencies in the global market place. Built to challenge the traditional model, Arcadia has scaled to a multi-million dollar run rate in under a year through disciplined execution, selective partnerships, and consistent, elite-level performance. The business is designed for precision, output, and scale. Our footprint spans North America from coast-to-coast, with presence in Toronto and New York as well as key U.S. markets including Charlotte, Boston, San Francisco, Atlanta, and Miami. We partner with companies backed by leading venture firms including Y Combinator, Andreessen Horowitz, General Catalyst, Founders Fund, Accel, and GV, delivering talent that directly impacts outcomes at the edge of innovation. At the same time, we work with mid-market and enterprise organizations across North America, enabling access to the same caliber of talent, speed, and precision required to compete in an AI-driven landscape. Arcadia sits in a category that is not widely accessible, nor easily replicated. Built on Trust. Delivered with Discipline. Rooted in Integrity.