Anthropic's CI job volume grew 25x in six months — here's how they scaled test selection

JeremyCMorgan · x · 2026-09-25

Anthropic engineers now ship 8x more code per quarter than the 2021-2025 average, with Claude authoring 80% and heavily involved in review. Tests grew 10x, engineers barely grew — and CI job volume exploded 25x in six months. Their fix: rebuilt test impact analysis with deterministic test selection based on per-test history. Three quick fixes lasted 70 days, 29 days, and under a day before a full architecture redesign held. Planning rule of thumb: assume 25x load in two quarters.

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