Claude Code now runs daily maintenance on Anthropic's software with a 46 percent merge rate

Details

Boris Cherny, the Anthropic engineer who built Claude Code, reports that the tool has been running daily automated maintenance on all of Anthropic's in-house apps for several weeks. Claude operates through a dedicated Slack channel called proj-claude-maintains-apps, executing 12 distinct maintenance routines across iOS, Android, desktop, web, CLI, and the Agent SDK. The routines span the full range of code upkeep: a Crash Fuzzer opens real apps in simulators and taps randomly to trigger crashes then proposes root-cause fixes; a Dead-Code Remover strips unreachable code but adds logging first for suspicious cases to verify the next day; a Flaky-Test Fixer analyzes unstable CI tests; a Dup Unifier proposes merging similar abstractions; a Shipped-Feature Inliner removes feature flags after full rollout. Critically, the prompts driving Claude are plain-language Slack messages — no elaborate prompt engineering. Of 388 pull requests created, 180 (46%) were merged after automated Claude Code review plus human review. Cherny calls results 'surprisingly positive' and frames it as 'early signs of life' for agentic maintenance — deliberately modest language that makes the metric more credible, not less. The 46% rate sits well below rubber-stamping territory while demonstrating real autonomous utility at production scale.