Rakuten Accelerates Software Development by 79% with Claude Code AI-Powered Autonomous Coding

Rakuten, a leading Japanese technology company with 70+ businesses spanning ecommerce, travel, fintech, digital content, and communications, faced mounting pressure to accelerate development velocity while serving millions of customers. With thousands of developers contributing across the organization, the company needed AI tooling that could reliably handle complex, multi-language codebases while maintaining enterprise-grade quality and security standards. Existing AI coding solutions required constant human guidance and lacked autonomy to tackle Rakuten's sophisticated engineering challenges, creating a bottleneck in their ability to innovate at scale.

Rakuten adopted Claude Code, an AI-powered development platform from Anthropic, fundamentally redesigning software development workflows around autonomous coding capabilities. Teams integrated Claude Code across the full development lifecycle—writing unit tests, mocking APIs, building components, fixing bugs, and generating documentation. The platform's autonomy proved transformative when Machine Learning Engineer Kenta Naruse assigned it a complex task: implementing an activation vector extraction method in vLLM, a 12.5-million-line open-source library spanning multiple programming languages. Claude Code completed the entire implementation in 7 hours of autonomous work in a single session with 99.9% numerical accuracy compared to reference implementations, demonstrating it could reliably handle Rakuten's most advanced technical challenges without requiring constant human intervention.

The deployment delivered substantial business impact across the organization. Engineering teams reduced average time to market for new features from 24 working days to 5 days—a 79% reduction—fundamentally transforming how Rakuten delivers innovation to customers. Claude Code enabled parallel development workflows, allowing teams to run multiple coding sessions simultaneously and eliminate bottlenecks. Beyond speed, the platform democratized development capabilities: non-technical employees leveraged Claude Code's terminal interface to contribute to coding projects without directly editing code, expanding innovation capacity across the organization. Rakuten's success has inspired increasingly ambitious initiatives, including building ambient agents that orchestrate 24 parallel Claude Code sessions to manage complex monorepo updates that would typically require over a month of manual effort.