Substrate AI Is Hiring Harness Engineers

What they're building

Substrate, a startup focused on AI for medical billing, is advertising for a Harness Engineer on Y Combinator’s jobs board. It has been reported that the company describes itself as building the “world’s first AI native BPO” for healthcare revenue cycle management and allegedly touches over 500,000 claims each month. Short version: they’re trying to wrap AI agents around one of the messiest, most lucrative corners of healthcare — and they want engineers who can make that work in the wild.

The job in a nutshell

The role centers on building the systems that sit around AI agents and production models: orchestration, success-rate improvements for probabilistic systems, precision for deterministic ones, and tooling to navigate EDI companion guides, complex contracts, and sensitive banking and healthcare infrastructure. It has been reported that the team expects the engineer to enable agents to make intelligent claims-processing decisions — the day-to-day stuff that decides whether a provider gets paid or does not. Sounds niche? It is. But it’s also the kind of gnarly, high-impact work engineers love or run from.

Why it matters

AI agents in regulated industries are the next big test for applied ML — can they be reliable, auditable, and fast enough to replace tedious human tasks without breaking compliance? Substrate says it’s going after a $14B outpatient RCM market and that the team brings deep healthcare, AI, and full‑stack experience. It has been reported that they view this as a way to help providers “get paid fairly.” Whether that promise pans out is another story. For now, the listing is a clear signal: startups are moving AI from experiments into mission-critical infrastructure — and they need engineers who can tame the chaos.

Sources: ycombinator.com, Hacker News