Anthropic says nobody needs a full mental model of Claude Code

Anthropic detailed how the Claude Code team handles code review now that Claude writes about 90% of the code. The team says no one keeps a complete mental model of the codebase, instead asking Claude to generate explainers for specific slices.

• Claude writes roughly 90% of Claude Code itself
• Merged changes in the monorepo rose from ~2,500 a day in May to 30,000+ in September
• About 59% of reviewer flags were on code that predated the first review pass
• One CLI PR went through more than 50 rounds of review and fixes overnight