Reference
The files coding agents read, measured
Most advice on CLAUDE.md and AGENTS.md comes from one person's repo. We counted 1,787,176 public files instead, then read 680 of each to see what goes in them. Each page answers the questions people search for, with the numbers and a source beside every claim.
CLAUDE.md
843,944 public files counted. The median runs 88 lines, and 51.6% were never edited after the first commit. How Claude Code resolves it, and where it stops working.
AGENTS.md
943,232 public files counted. The median runs 67 lines, and 61.4% were never edited after the first commit. Which tools read it, and how it differs from CLAUDE.md.
How we counted. Measured 28 September 2026 against the public GitHub corpus. Size distribution from code search result counts across 17 size buckets, which covers every public file rather than a sample. Content from 40 files per bucket, 680 per filename, reweighted to that distribution. Upkeep from the commit history of 246 root-level files per filename. Private repositories are out of reach, and code search ranks by popularity, so the upkeep figures describe repositories with some traction rather than the long tail.
If you want the file kept current rather than measured, read how Trail works for coding agents.