Anthropic's Claude Code lead says the review, not the writing, is now the bottleneck

Boris Cherny, who leads Claude Code at Anthropic, told Fortune at a Brainstorm Tech fireside chat that he has not written code by hand in about eight months: "Claude Code, 100% written by Claude Code." He said he was managing a few hundred agents the morning of the talk, and some days manages tens of thousands. He describes what he calls the bottleneck migration problem: automating one stage of software delivery does not remove friction, it relocates it. At Anthropic, code writing was the first bottleneck and Claude Code eliminated it; code review became the new constraint, addressed with a team of differently-instructed Claude reviewers plus a human approval step; maintainability and security followed, addressed with automated Claude-driven improvement routines and a Claude Security scanning product. Anthropic's own blog post on the subject puts the resulting code-output increase at roughly 8x over a 2021 to 2025 baseline, with the caveat, quoted in the piece, that the figure is "almost certainly an overstatement" because counting lines of code rewards volume, not quality.

Cherny also named an organizational cost: new engineers on his team talk to Claude so often that they see less of their colleagues, which has led Anthropic to "consciously" push human pair programming and social time.

Why it matters: Anthropic's own blog calls the self-reported 8x figure likely inflated. The operational sequence is more useful: code generation moved the bottleneck to review and maintainability, and Cherny's team responded with differently-instructed reviewing agents plus one human sign-off.