Founding Engineer | AI-Native Mental Health Care; backed Y Combinator ARR raised

About Legion Health

Legion Health (backed by Y Combinator) is building autonomous mental healthcare—AI that takes real responsibility across the full care loop: before the visit, during the visit, and after the visit. We run our own psychiatric practice, which means we ship into reality—not theory. We’re rebuilding the patient experience end‑to‑end.

• Outside the visit: scheduling, intake, benefits checks, paperwork, reminders, care coordination, billing, risk detection, follow‑ups, and patient messaging
• Inside the visit: visit support, real‑time note scaffolding, structured history capture, differential reasoning support, diagnostic signal extraction, treatment planning assistance, medication decision support, and clinician workflows that make great care feel effortless

I’m hiring a Founding Engineer to own core product and agent systems end‑to‑end. You’ll build the layer that coordinates patients, clinicians, and AI agents as one coherent machine—tight feedback loops, high standards, and real ownership.

This isn’t just infra. It’s building the product heart of an autonomous care system: the workflows, the agent behaviors, the guardrails, the integrations, the UX that makes it usable, and the reliability that makes it trusted.

We’re looking for someone who wants to carry real weight, take full ownership, and grow into running major parts of the system—not someone who needs a perfectly scoped box to operate.

• Own our event‑driven backend – architect and scale our Node.js / Type Script / Supabase (Postgres) / AWS stack. Design schemas, in variants, and workflows that encode how psychiatric care actually operates. Turn messy real‑world processes into clean state machines and event streams.
• Build real LLM agents as coworkers – implement tool use, retries, memory, and safety rails. Design action schemas and evaluation loops so agents can run reliably in production. Work on orchestration, context management, and multi‑step workflows.
• Shape human + AI ops UX – build internal tools used by both humans and agents. Make it trivial to see “what happened, why, and what should happen next” in any patient journey.
• Define world‑state & simulation – model the canonical state of a patient’s journey across time. Power alerting, routing, and decision‑making from that live simulation.
• Own data, safety & compliance – engineer HIPAA‑compliant pipelines for transcripts, events, and EHR data. Ensure PHI access, agent actions, and human overrides are all auditable.
• Drive architecture & strategy – work directly with the CTO to debate tradeoffs, define new primitives, and decide what we build next.

• You’ve owned real systems 0→1 or 1→N, not just tickets.
• You think in events, state, and in variants, not just CRUD endpoints.
• You’re either already LLM‑fluent or a strong systems/backend engineer who can get dangerous fast.
• You care about velocity and correctness—moving quickly while keeping things understandable and robust.
• You like small, high‑candor teams and direct feedback.
• You want to see your work go live in production weekly, not sit on a roadmap.

• Experience with Node.js / Type Script, Postgres, or Supabase.
• Experience with LLMs, agents, tool‑calling, or RAG.
• Experience in healthcare, fintech, or other regulated / high‑stakes domains.
• Experience in early‑stage startups or founding teams.

• Backend:
  Node.js, Type Script, Supabase (Postgres), AWS (ECS, Lambda, S3)
• Frontend:
  Next.js 15 (App Router), Tailwind, Vercel
• AI:
  OpenAI, Anthropic, tool‑calling agents, embeddings + vector DBs, Langfuse‑style observability
• Other: PHI security, audit trails, real‑time schedulers, transcript ingestion

• Job type:
  Full‑time
• Role type:
  Engineering
• Ideal Experience Level: Doesn’t matter if you’re cracked
• US Visa Sponsorship:
  Yes
• Salary: $140,000–$220,000 (based on experience)
• Early‑Stage Equity: 0.2%–0.8% meaningful early ownership
• Health Insurance:
  Medical, dental, and vision benefits
• Additional Perks:
  In‑person retreats, meal stipends, etc.
• Time Off:
  Flexible, unlimited vacation policy
• Work Hours:
  
  Flexible…