Anthropic says Claude writes about 90% of Claude Code's own code. From June to September, merged PRs more than doubled and reverts fell by over 40%. Your first instinct is probably "sure.
Source: [Dev.to](https://dev.to/ashraf_chowdury09/claude-code-is-90-ai-written-heres-the-7-layer-code-review-system-that-keeps-it-from-collapsing-2jg2)