RL Engineer

About This Opportunity

About Ethos

We're building AI to make humans irreplaceable. Ethos is the platform that matches human expertise to paid opportunities, from AI model training to advisory roles and full-time positions, backed by a16z, General Catalyst and other top investors.

What You'll Work On

• Designing and building RL environments and data generation pipelines that feed into post-training workflows
• Agentic infrastructure that sources, screens, and routes domain experts at scale
• Evaluation frameworks to close the loop between data quality and model performance

This is an early-stage role with meaningful equity. If you've built things that matter at companies that didn't have all the answers, we'd love to talk.

Key Requirements

• Hands-on experience building RL environments or generating data for post-training (RLHF, RLAIF, preference data, evals) — this is central to the role
• Startup experience — you've shipped in resource-constrained environments and taken real ownership
• Strong background building AI/agentic applications (LLM pipelines, tool use, evals)
• Generalist instincts - you'd rather solve the problem than protect your lane
• Comfortable across the stack: backend, infra, and ML tooling