Projects | Tatsuya Sasaki - Strategy-to-Code Builder | Tatsuya Sasaki

All Work

Case studies in enterprise systems, AI agent organizations, and UX design.

sagi-shield — A 'Secretary Button' That Verifies Suspicious Contacts

Web App — 2026

My second submission to the 5th Agentic AI Hackathon with Google Cloud. Special fraud costs Japan over ¥70 billion a year, and most victims weren't fully fooled — they felt a thin suspicion but had no one to check it with. sagi-shield is a button you press in that moment: an AI that always introduces itself as 'your AI security secretary,' then verifies the caller's name, organization, official number, and purpose — live on a real phone call via Gemini Live API — while logging everything to an evidence ledger, notifying family over LINE on danger, and generating a police-consultation (#9110) report. Verified end-to-end on a production acoustic path; the deterministic detection layer is calibrated at 100% catch / 0% false-positive on the test corpus.

Real-time Voice AI · Agentic System Design · Safety-Critical UX

Water Damage Claim Pack — AI Re-Judges Every Photo Against 8 Evidence Slots

Web App — 2026

A submission to the 5th Agentic AI Hackathon with Google Cloud. When water damage hits a home, cleanup destroys evidence before anyone photographs it properly — and insurance claims shrink or get denied for missing proof. This agent re-judges every uploaded photo against all 8 evidence slots used in claims assessment (room overview, mid-shot, close-up, water path, secondary damage, date proof, contrast boundary, scale reference), refuses to let unrelated photos fill a slot, and outputs an inspectable ZIP pack with photos, checklist, and manifest.json. Built, reviewed, and submitted in a 9-day sprint; live at water-damage-claim-pack.web.app.

Agentic Workflow Design · Multimodal AI Integration · Evidence Schema Design

Agent Ops Warehouse — A ¥0 BigQuery Data Platform for AI-Agent Telemetry

Web App — 2026

A personal, Terraform-managed BigQuery data platform that turns my own operating history — 188 commits across 5 personal repositories, 20 published articles, and locally-aggregated lesson and session records (sources limited to personal repositories and personal logs by an explicit allowlist) — into queryable evidence, plus a Cloud Run RAG API for asking questions over the published corpus. Built and run entirely on GCP's free tier by design: 71 dbt tests passing, 144 automated tests passing, and 5/5 known-question retrieval accuracy. (Commit/article counts as of 2026-08-13.)

Data Warehouse Design · Infrastructure as Code · Retrieval-Augmented Generation

A 12-Agent AI Organization — Designing How AI Works

Web App — 2026

I don't just use AI — I run an organization of it: 12 specialized AI agents with distinct roles, personas, and rules of engagement, governed by a constitutional rulebook evolved over 30 versions. It handles research, drafting, verification, and operations in my daily strategic-planning work, with 18,000+ actions logged over two years of production use.

AI Agent Orchestration · Constitutional Governance · Prompt Engineering

Enterprise Expense Automation — 70+ Daily Users, Solo-Built

Web App — 2026

An expense management platform for a large manufacturing division: automated monthly data collection, reminders, aggregation, and executive dashboards across 90+ organizational units. Solo-designed and built on Google Workspace with defense-in-depth safety architecture. 70+ people use it daily; the investment paid for itself in about a month.

Business Process Automation · Data Pipeline Design · Safety Architecture

PLM Digital Thread — 143K Lines, 430x Faster, Built Solo

Web App — 2024

A cloud-native product master data platform for a flagship door product line: 999 product specifications × 58 attributes, unified across 51 BigQuery tables and serving 4 global factories. Designed, implemented, tested, and documented by one person — with queries 430x faster than the system it replaced.

Data Architecture · Test-Driven Development · BOM Management

This Site — A Portfolio That Is Its Own Case Study

Web App — 2025

The site you are reading is itself a production system: migrated from a no-code builder to Next.js on Vercel, cutting hosting costs while gaining full control — then hardened with 6 automated test suites, visual regression, and CI. Maintained through the same AI-native workflow I use at work.

Full-Stack Development · Test Automation · CI/CD

UX Foundation

Research and design work from my UX Designer diploma (EQF Level 7) — the training that still grounds how I define problems today.

Use Analytics to Inform UX Design - Google Merchandise Store

UX Design — 2023

A project from my OpenClassrooms UX design course. I took the course brief — a branded e-commerce site (Google Merchandise Store) that had never looked at its Google Analytics, with a new charity campaign coming up — as a real assignment, analyzing actual Google Analytics data to evaluate the site's performance and propose improvements.

Data Analysis · Google Analytics · UX Design

Design an App to Combat FOMO - Event Discovery App

UX Design — 2023

A project from my OpenClassrooms UX design course. I interviewed people who might experience FOMO (fear of missing out) and used the problems I uncovered as the inspiration for an app concept.

UX Design · Persona Creation · User Journey Mapping

Improve an Existing Product - Kopernik Website Redesign

UX Design — 2023

A project from my OpenClassrooms UX design course, working on the real non-profit Kopernik's website landing page in a 2-week sprint cycle. I organized the roadmap and tasks, investigated mental models and usability issues through card sorting and usability testing, and proposed multiple design alternatives.

UX Design · Information Architecture · Usability Testing

Usability Test Your Dream Vacation - Hoshinoya Karuizawa Website

UX Design — 2022

A research project from my OpenClassrooms UX design course. I chose a hotel website that looked like it had room for improvement and ran usability testing and a heuristic evaluation to identify what to fix.

Usability Testing · User Interview · Card Sorting

Conduct Research Around Coffee - Japanese Coffee Market Study

Research — 2022

A research project from my OpenClassrooms UX design course. Working from a course brief framed as "a multinational coffee brand is considering expanding its product line," I studied how people in Japan drink coffee through ethnography and user interviews, then synthesized the findings through competitor analysis, personas, and journey mapping.

User Research · Ethnography · Persona Creation