Agent Harness Engineer English (RT)

Design the Heart of the Enterprise Brain. Build the Next-Generation Execution Engine and Guardrails for Advanced AI Agents!Residents of Japan

Job Title

Agent Harness Engineer

Company Overview

We are a fast-growing elite AI startup specializing in cutting-edge enterprise SaaS platforms powered by Generative AI. Our product team manages a sophisticated environment supporting hundreds of concurrent workflows entirely in-house. We pride ourselves on a highly creative collaborative environment where engineering and AI research intersect providing our teams with massive scale and the freedom to design the industrys most advanced AI agent control frameworks.

Your Role and Responsibilities

Design and implement the core execution engine (Graph Runtime / State Machine) based on a deep understanding of LLM and AI agent operating principles.
Own AI-specific system architecture managing model routing context processing and memory infrastructure (both long-term and working memory).
Design and develop a robust Agent SDK to be utilized internally by our engineering organization.
Build a secure guardrail and policy execution engine to guarantee safe quick and reliable agent operations.
Partner with Research Engineers to continuously integrate state-of-the-art research outcomes into our production infrastructure.

Experience and Qualifications

Bachelors degree or equivalent practical experience in Computer Science Software Engineering Artificial Intelligence Machine Learning Mathematics Physics or related fields.
5 years of practical experience as a Backend Engineer.
Strong hands-on production product development experience using Python.
Proven experience designing and implementing production systems that leverage LLMs and AI agents.
Hands-on experience designing and coding distributed systems from scratch (not just operating them).
Professional experience designing and implementing RESTful APIs and gRPC.
Language skills: Fluent Japanese (ability to discuss product development without friction) OR Business-level English.

Tech Stack

Languages: Python Go (Backend / Infrastructure) TypeScript / React / (Frontend) NX
Infrastructure & Messaging: GCP (Containers / K8s) Docker Terraform Kafka Pub/Sub
Monitoring & Tools: Prometheus Grafana OpenTelemetry GitHub Slack Confluence Linear Notion
AI Dev Support: Claude Code MAX Plan Cursor ChatGPT Devin
Workstation: Mac (Apple Silicon) dual monitor setup

Good Reasons to Join

**Elite AI Support:** Stay at the absolute cutting edge with full company coverage for top-tier AI dev tools including Claude Code MAX Devin Cursor and ChatGPT.
**Learning and Growth:** Generous book purchase assistance (30000 half-yearly) language learning programs and qualification acquisition coverage.
**Flexible Hybrid Culture:** Work 3 days in the office and 2 days remotely supported by flexible hours and negotiable core times.
**Exceptional Benefits:** Includes a monthly refresh allowance (5000 for gym movies etc.) dedicated housing support (up to 30000/month) and standard development tool support.
**Financial Upside:** Competitive salary structure with stock options available alongside biannual performance evaluations and bonuses.

Work Location

Tokyo (Hybrid Work: 3 days office 2 days remote)

Salary

(Based on experience; bonuses and stock options available)