Kochi University Student Sakashita Yasunobu Built an Event-Driven AI Investigation Harness During an Internship at Japan's LINE Yahoo Corporation

Generative AI has dramatically accelerated code writing speed, but the SRE team for LINE Gift at Japan's LINE Yahoo Corporation found that new bottlenecks had shifted to processes outside code generation: initial alert triage, branch operations, and code convention fixes. Sakashita Yasunobu, a fourth-year student in the Faculty of Humanities and Social Sciences at Kochi University, interned on this team from August to September 2026. The core problem he tried to solve: how to let AI initiate investigations automatically triggered by events rather than waiting for human prompts, while ensuring it cannot cause damage.

Sakashita decomposed this into three layers. The first is purely mechanical automation: propagating changes from the main branch to all active branches automatically, using GitHub Actions to create and merge Pull Requests every morning. The second is AI-assisted development environment improvement: introducing mutation testing to quantify E2E test detection capability, using Lefthook to intercept unintended AI-generated output before commits, and migrating existing shell script tools to Go and Python for better maintainability. The third is what he truly wanted to build — letting AI complete initial investigations autonomously without step-by-step human instructions.

The key concept of the third layer is the harness. Sakashita wrote in the article: building AI utilization infrastructure is not simply about introducing high-performance models; what matters is preparing an environment where damage can be contained even if AI fails, along with feedback mechanisms to detect failures, so that AI can perform within the range humans intend. Specifically, his harness includes three types of constraints: hard limits on execution steps and timeouts to prevent infinite loops from wasting API calls; permission separation, allowing reads of logs and metrics while blocking destructive writes; and container isolation, so that even if the execution environment is compromised, the impact is contained within the container.