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Pax Historia is building a platform for worldbuilders, storytellers, and game developers to create and publish interactive 'what if' scenarios. The platform has grown to 25k+ published presets, 92 million rounds played, and is backed by Y Combinator (W26), Bessemer, Pace Capital, and others following a 10M+ seed round in March 2026.
In this founding engineer role, you will focus on harness optimization—improving how AI models generate engaging, consistent storytelling within games. Currently, the platform processes ~240B tokens weekly across 37+ different AI models, but uses largely uniform default workflows that don't adapt to each model's unique strengths and quirks. Your mission is to unlock significantly better game experiences by optimizing prompt architecture, workflow design, and model-specific tuning.
Day one involves experimenting with workflow architecture and prompts to drive measurable improvements, while building evaluation frameworks to determine whether changes actually make games more interesting and narratively coherent. You'll work on the intersection of AI systems, creative storytelling, and empirical optimization—balancing long-term consistency with creative developments that keep players engaged.
You'll be the 7th team member in a lean, fast-moving startup. The role demands someone who is deeply experiment-driven, thinks in systems, and understands storytelling fundamentals. While you don't need prior experience in this exact domain, you must have strong fundamentals, be a fast learner, and thrive in ambiguity. The company is open to visa sponsorship.
Requirements:
- Extremely experiment-driven mindset with ability to design and iterate on evals
- Strong systems-thinking and ability to reason about complex AI workflows
- Fast learner with strong fundamentals in machine learning, prompt engineering, or related fields
- Understanding of or passion for storytelling and narrative design
- Ability to work in-person in San Francisco 5+ days/week
- Visa sponsorship available
