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arXiv · 2512.05314

WhatsCode: Large-Scale GenAI Deployment for Developer Efficiency at WhatsApp

Ke Mao·Timotej Kapus·Cons T Åhs·Matteo Marescotti·Daniel Ip·Ákos Hajdu·Sopot Cela·Aparup Banerjee
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Abstract

The deployment of AI-assisted development tools in compliance-relevant, large-scale industrial environments represents significant gaps in academic literature, despite growing industry adoption. We report on the industrial deployment of WhatsCode, a domain-specific AI development system that supports WhatsApp (serving over 2 billion users) and processes millions of lines of code across multiple platforms. Over 25 months (2023-2025), WhatsCode evolved from targeted privacy automation to autonomous agentic workflows integrated with end-to-end feature development and DevOps processes. WhatsCode achieved substantial quantifiable impact, improving automated privacy verification coverage 3.5x from 15% to 53%, identifying privacy requirements, and generating over 3,000 accepted code changes with acceptance rates ranging from 9% to 100% across different automation domains. The system committed 692 automated refactor/fix changes, 711 framework adoptions, 141 feature development assists and maintained 86% precision in bug triage. Our study identifies two stable human-AI collaboration patterns that emerged from production deployment: one-click rollout for high-confidence changes (60% of cases) and commandeer-revise for complex decisions (40%). We demonstrate that organizational factors, such as ownership models, adoption dynamics, and risk management, are as decisive as technical capabilities for enterprise-scale AI success. The findings provide evidence-based guidance for large-scale AI tool deployment in compliance-relevant environments, showing that effective human-AI collaboration, not full automation, drives sustainable business impact.

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Ke Mao, Timotej Kapus, Cons T Åhs, Matteo Marescotti, Daniel Ip, Ákos Hajdu, Sopot Cela, Aparup Banerjee. 2025-12-04. WhatsCode: Large-Scale GenAI Deployment for Developer Efficiency at WhatsApp. https://arxiv.org/abs/2512.05314

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