Shopify's Internal Coding Agent 'River' Now Generates 50%+ of Code — Operates Entirely in Public Slack

Simon Willison's Blog·high signal

Tobias Lütke described Shopify's internal AI coding agent River, which refuses DMs and operates exclusively in public Slack channels, making every prompt-response pair searchable company-wide. Over 50% of Shopify's code is now AI-generated through River. Key insight: senior engineers with thousands of problem-solving repetitions are significantly better at prompting River than newer employees — suggesting AI amplifies experience rather than replacing it. The public-by-default design turns the tool into an organizational learning system.