Principal Engineer (backed by Y Combinator, $5M+ ARR, $23M+ raised)

The role

Hey, I'm Daniel G Wilson, co-founder and CTO at Legion. I studied applied math and CS at Princeton, led the Office Scripts and Power Automate integration at Microsoft, and did deep learning and RL research before that. GitHub: https://github.com/danielgwilson

I'm hiring a principal-level engineer to own the hardest systems in our care platform, whole. Not tickets, not a lane inside someone else's architecture: entire problem spaces, from "this is a mess" to "this is done and here's the doc."

Here's the honest shape of the job. We run a regulated clinical product (we e-prescribe controlled substances) on an event-driven TypeScript platform, and we ship at unusual velocity with heavy agent leverage. The engineers who have thrived here share one behavior: I hand them a gnarly domain, they disappear into it, and they come back with it working, documented, and theirs. I don't need to check their work or meddle, because checking isn't unnecessary. That's the seat. The people who have struggled here waited for scoped tickets to tell them what to do-but that's what we have agents for.

• What you'll own

Real domains, picked together in week one from this list, with written authority over them:

• The factory spine. Own the question of how we get maximum leverage in the era of agentic engineering. We ship 500-1,000 PRs a month with a lean team. Merge gates, migration safety, canary and rollback on a system where a bad deploy can touch patient care-this all works today. Your job will be to move us towards 10,000 while maintaining quality and rigor.
• The clinical work spine. Our event-sourced system of record for clinical work (orders, tasks, commands, receipts): the layer that lets AI agents and humans act on patient care with auditability and fail-closed checks. You'll own the guardrails that ensure agents can safely provide broader and broader components of care.
• Agent operations in production. LLM agents doing real clinical-adjacent work with tool use, checks, and receipts. You decide how autonomy expands and ratchets upwards as proof accumulates. Your agent harness will help prescribe psychiatric medication, legally, at the second company ever allowed to.
• The data and metrics estate. Warehouse, analytics platform, and the pipelines that tell us what actually happened.
• Architecture syncs with me. You'll have the standing I give someone who has seen more systems than I have: disagree with me, make the call in your domain, unpack it for the team when asked.

What "a fit" looks like, concretely

• You've owned architecture across multiple companies or many codebases: staff-plus IC, chief-architect, or platform-consulting background. You've seen a dozen ways teams ship and you have opinions with scars behind them.
• You ship daily at high volume with a fleet of AI agents. That's table stakes. In the interview we'll ask to see your actual setup and what you let it do unsupervised. "I use Copilot sometimes" is not this.
• When handed an ambiguous, ugly, load-bearing problem, your instinct is to take it whole: read everything, decide, build, write the doc, tell us what you decided. Not to schedule a meeting about scope.
• You communicate proactively in writing. The pattern we love: a Sunday text that says "took care of it, here's the PR and what I changed."
• You hold clinical-grade correctness without losing speed: auditability, HIPAA, fail-closed defaults, invariants over vibes.

This is a senior seat. Typically that means 10+ years and multiple systems owned end to end, but we care about the scars, not the number. We have separate openings for earlier-career engineers; this is not that. We need someone who's seen some shit.

This role is not for you if you want to manage instead of build, you need well-scoped tickets to be productive, or big-company pace feels normal to you.

Our Tech Stack

• TypeScript, Node.js, Postgres, Next.js on Vercel, AWS, production LLM agent orchestration and bespoke harnesses, tools, CLIs, skills, evals and observability, EHR and e-prescribing integrations, PHI-grade security and audit trails.

Process (7 to 10 days)

• Process (7 to 10 days)
  
  1. Coffee chat (20 min). We discuss the hardest engineering systems you've owned, earned scar tissue, and whether there's mutual interest and fit at a high level.
  2. Systems deep dive (60 min). You walk me through one or two systems you owned for years: architecture, tradeoffs, what broke and what you changed.
  3. Take-home (async). You receive a simplified slice of our real repo and system surface, identify an area you'd like to shore up / build out / rearchitect, and execute. The deliverable will be a PR with an implementation (not a plan) and your agent session logs.
     
     • [Alternate] Paid work trial (2 to 5 days, flexible around your current job). A real domain from our actual backlog, in the real repo, with your own agent tooling. This is the interview. It's how our best people got hired, and it's how you find out whether you want this.
  4. Interviews with founders and engineering. You'll meet the rest of the talented team you'll work with here at Legion.
  5. Decision within 48 hours. Written offer or a written no with the reason.
• Apply: https://jobs.ashbyhq.com/legionhealth/115954a2-dc13-4a9c-98b6-14fede7b7852 or email me directly with a system you're proud of.
• Start date: ASAP

Role Logistics, Compensation, and Benefits

• Job type: Full-time
• Role type: Engineering
• US Visa Sponsorship: Yes
• Salary: $250,000 to $400,000 depending on experience, plus meaningful early-stage equity.
• Health Insurance: Medical, dental, and vision benefits
• Additional Perks: In-person retreats, meal stipends, etc.
• Time Off: Flexible, unlimited vacation policy
• Work hours: flexible but demanding-because we are (literally) saving lives.
• Work Setup: In-person @ San Francisco HQ; partial remote considered for exceptional candidates (our track record includes both).
• Impact: Work on something that truly matters to millions of patients and families.
• Autonomy and Learning: Ownership over your projects with the freedom to set priorities, shape processes, and drive outcomes end-to-end.
• Growth Opportunities: As we scale, we envision our top performers stepping into expanded roles and joining our executive leadership team.