AI Product Engineer (LLM New Product)

This role develops one of Loglass’s new AI products for business decision-making and operational workflows. The engineer works with product managers, designers, domain experts, and business members to understand customer work and problems, design the product experience, define requirements, and deliver working software.

Responsibilities cover customer interviews and workflow observation, hypothesis testing with prototypes, product design, implementation, validation, and continuous improvement. The role includes designing and building web applications that incorporate LLMs, prompt and context engineering, and retrieval-augmented generation (RAG). It also involves designing workflows and user experiences with AI agents, creating evaluation methods and metrics for model output quality, and improving accuracy, speed, cost, and reproducibility. The engineer tests new models and AI technologies, prioritizes work using usage and qualitative or quantitative data, contributes to development plans and product roadmaps, and helps build reusable technical foundations across AI products.

The work spans frontend, backend, AI applications, and architecture according to the product phase and the engineer’s strengths. It includes architecture for availability, scalability, security, and performance, as well as code review, test design, automation, and development-process improvements using AI coding tools. The products are being developed for specialized, information-intensive areas of corporate activity, including investor relations and sales, and may involve SaaS or enterprise product contexts.

The required background is at least five years of experience designing, developing, and operating web applications. Candidates must have experience understanding customer or business problems and developing solutions, independently advancing design, implementation, testing, and release in a small team, improving development quality through code review, collaborating with product, design, and business roles, and progressing product development through hypotheses when specifications are not fully defined. Desired experience includes new businesses, 0-to-1 or PMF-stage products, LLM, generative AI or AI-agent products, prompt or context engineering, RAG, AI application quality improvement, React, Next.js, TypeScript, Go, SaaS or enterprise products, customer interviews, technical selection, architecture leadership, TDD, DDD, clean architecture, and AI-assisted development with Cursor, Claude Code, or Gemini.

The position is full-time with a three-month probationary period, extendable to six months. Annual compensation is listed at ¥7,000,000–¥20,000,000 and is determined based on experience and skills; salary reviews are held twice yearly. Working hours are 10:00–19:00 with a one-hour break and a flextime system with core hours from 10:00 to 15:00. The work location is the Tokyo office in Minato City, with domestic remote work available. Holidays include Saturdays, Sundays, public holidays, and year-end and New Year holidays from December 28 through January 3. Benefits include company-leased housing, equipment support for PC-related items, and a corporate defined-contribution pension plan. Insurance includes health, employees’ pension, employment, and workers’ compensation insurance.