Armature study: how Claude Code, Codex and Cursor pick tools
Armature, a developer-tool growth services company founded in 2026, published a study of how coding agents choose third-party tools, testing Claude Code, Codex and Cursor across 75 public repositories with 1,163 prompts built to simulate different developer personas; the company says its public core figures come from a verified subset of 5,292 sessions out of roughly 17,000 in total. Repository context mattered heavily: for email/communications providers, Resend won in TypeScript (55 of 89 runs), SendGrid in Python (22 of 24), Postmark in Go (20 of 24) and Azure ACS in Java (22 of 23), while the three agents picked the same tool in only 42% of test units and Claude Code chose to build something itself almost twice as often as Codex and Cursor (19% vs 10%). The agents also drew on different information sources — Codex used web search in 94% of sessions, Cursor relied on web information in about two-thirds, and Claude Code leaned mainly on its own knowledge, searching only around 30% of the time but visiting three times as many pages as Codex when it did browse.
If agents rather than people increasingly decide which tools get adopted, two decades of human-facing brand building may count for little and vendors may need to rewrite docs and pricing pages for machine readers.