Frontend Engineer

About Citadel AI

Citadel AI builds software products to evaluate, monitor, and govern AI systems. Our mission is to make the world’s AI systems more reliable and trustworthy.

We’re located in Tokyo, but we have an international team and global customers. Our goal is to build a world-class startup from Japan, and our team members have previously worked at leading companies such as Google, Paidy, Apple, Stripe, and Meta.

This is a unique opportunity to join a team in Tokyo building new products for a global market. As an early employee at Citadel AI, you’ll have significant impact and ownership over the growth of our startup. We’re supported by Japan’s best investors and a top-tier enterprise customer base, and are currently scaling our business in the 1 → 10 stage.

About the role

We’re hiring our second frontend engineer to work with our small, full-stack team to build products to evaluate, monitor, and govern AI systems. Our users rely on our product interfaces to visualize and understand complex details about their AI models, datasets, and workflows.

You’ll be responsible for designing and implementing product interfaces in our existing and new products, covering:

• Evaluation: Quantitative testing of AI models and datasets
• Firewall: Real-time monitoring of AI prompts and responses
• Governance: System-of-record for enterprise AI use cases and workflows

As we scale our products, team, and business from the 1 → 10 stage, you will also contribute to modernizing our codebase and scaling our engineering processes.

You’ll primarily work with Svelte and shadcn/ui for new features, and vanilla JS, Bootstrap, and Jinja for existing features. Some technologies we use are: TanStack, Chart.js, Sveltekit, Vite, JSDoc, TypeScript, Vitest, Playwright.

Job requirements

Our company, technology, and market are new and changing rapidly, so a large part of the job is to adapt and learn new things. We value learning fast over pre-existing knowledge (“slope is more important than y-intercept”).

You should have at least 3 years of frontend software engineering experience. We don’t require past experience with specific programming languages or frameworks, but knowledge of reactive frameworks such as React, Vue, or Svelte is desirable.

English is required and Japanese is preferred. We prioritize candidates in Tokyo, but may consider remote for exceptional candidates.

Nice-to-have: you can work full-stack, you’ve worked at a startup before, or you have AI/ML/LLM experience.