Founding Engineer—Build AI-Native Ops for Mental Health (YC S21, $1M+ ARR)

🧠 Build AI-native care infrastructure. Ship for real patients. Operate at speed.

ℹ️ TL;DR

We're building the AI-native operations layer for psychiatric care. Not diagnostics, but what happens outside the visit—the real operational backend: scheduling, documentation, billing, intake, risk detection, and more.

If you want to build core infrastructure with real AI, own systems end-to-end, and work directly with a deeply technical founder still up to his neck in the code—read on.

🗺️ Context

Hey—I'm Daniel, co-founder and CTO of Legion Health (YC S21).

Mental health care is operationally broken—patients ghosted, clinicians buried in forms, payers chasing missing notes.

The industry is flooded with AI startups trying to automate away diagnosis—and even providers as a whole. But diagnostics aren’t the bottleneck. Operations are.

So, we’re solving the real problem:

"What if operations worked?”

We’re building a real-time, AI-powered backend for mental health clinics—LLM agents + structured systems that coordinate human care like it’s software. Think:

• Automated intake that personalizes itself mid-call
• AI copilots that document visits while verifying insurance
• Risk detectors trained on full transcripts and events
• Schedulers that close the loop without human friction

And we’re already live. Our agent infrastructure supports over 2,000+ patients — with only one support human.

Unlike most AI startups, we are our own customer. We operate our own large psychiatric practice. The systems you build directly impact our clinicians and patients today. No theoretical B2B pitches, begging for pilots, and months of stakeholder alignment and bureaucracy—just real-world, high-stakes operational challenges.

⭐ If you've felt like AI is being wasted on toy tools or B2B busywork—come work on something real.

🏆 What we’ve already built

• $1M+ ARR, growing fast—post-PMF, pre-scale
• $6M raised, $3M in the bank
• A live agentic co-pilot (think “Cursor for care ops”) that actually reduces admin overhead
• A functioning psychiatric practice with real clinicians, patients, and claims
• A high-leverage AI architecture in motion—LLM tool use, RAG, event-driven infra
• A clear path towards for an event-driven, simulation-capable architecture that self-improves
• A small, intense team (~11 people) shipping daily—no dead weight

This is the moment where foundational hires make the company. You're not joining an idea-stage pipe dream or a late-stage dinosaur. You're helping us define the future.

👷🏻‍♂️ What you’ll build and own

This isn't a feature factory. We move fast, shipping multiple meaningful features straight to real patients and providers every single day.

You’ll own entire domains end-to-end—architecture, implementation, iteration—not just JIRA tickets. This is the frontier of applied AI in healthcare.

• Core Event-Driven Backend: Architect and scale our Node.js / Next.js / TypeScript / Supabase (Postgres) / AWS stack. Design schemas, event flows, and APIs that power real-time, resilient psychiatric care ops.
• LLM Agent Infrastructure: Build actual agent loops—tool use, memory, retry logic, context updates, feedback mechanisms. Not a demo. A co-worker.
• Human + AI Ops UX: Shape real-time interfaces where human teammates and agents co-work, co-learn, and co-adapt. Agents learn by using the same UI our humans do.
• World-State Simulation: Define the canonical state of a patient’s journey. Power alerting, planning, and agent behavior with a simulation of psychiatric care at scale.
• Data & Compliance: Engineer secure, HIPAA-compliant pipelines for transcripts, events, and EHR data—structured for both operations and AI training.
• System Design & Strategy: You’ll work directly with Danny (CTO) to debate architecture, invent new primitives, and define the foundation for AI-native mental health systems.

You’ll help answer questions at the frontier of AI, like:

What does reliable agent infrastructure look like in production?

What’s the role of structured data in a world with LLMs?

How do we make agents auditable, evolvable, and fast?

🫵🏻 This is for you IF

• You've built and owned complex systems from 0 to 1—not just features but foundations
• You think in systems, state machines, and event flows—not just endpoints.
• You're LLM-fluent or are a strong systems engineer eager to become fluent fast.
• You default to velocity and appreciate clean architecture. Move fast and build resiliently.
• You're allergic to bureaucracy, performative work, and slow decisions.
• You hold an incredibly high bar for yourself and expect it from others. Mediocrity is painful.
• You want direct impact, technical depth, and to solve problems that have never been solved before.
• You believe AI today is the worst AI will ever be—and want to be a part of building the future.

We're not looking for warm bodies. We’re looking for founding technologists who can think in systems and ship fast.

🙅🏻‍♀️ This is NOT for you IF

• You need extensive structure, mentorship programs, or a predefined career ladder.
• You prefer working on a single, well-defined component.
• You view LLMs as just another API call.
• You're uncomfortable with ambiguity or rapid iteration.
• You can't handle direct, honest feedback or thrive in a high-candor environment.

⚙️ Our Stack

Backend:

Node.js, TypeScript, Supabase (Postgres), AWS (ECS, Lambda, S3)

Frontend:

Next.js 15, Tailwind, Vercel

AI Infra:

OpenAI, Anthropic, agentic loops and workflows, observability and eval (e.g. Langfuse), embeddings and vector DBs, tool-calling, model context protocol (MCPs), etc.

Other:

PHI security, audit pipelines, real-time schedulers, transcript parsing

🚀 Why Legion? Why Now?

This is the moment when the infrastructure is still malleable. When the next 20 years of mental health care can still be shaped by a few engineers with systems taste, speed, and conviction.

You won’t be joining as employee #73. You’ll be founding the engineering culture. You’ll have a direct line to me. You’ll shape core systems and help decide what we build next.

If you’ve ever said, “I wish I could’ve been there when [insert legendary product] was getting built,” this is that moment.

If this resonates, I want to work with you. Let’s build the founding systems of AI-native mental healthcare—and make something people didn’t think was possible.