CLAUDE.md
Claude Code's memory file. Shaped like AGENTS.md but with two things it lacks: @path imports, so shared rules live in one place, and a user-scope layer that follows the developer across repos rather than shipping with the code.
What the corpus measured
2026-08-03Repositories
248
2026-08-03Adopting repositories, not files.Share of corpus
35.7%
2026-08-03Of every repository RuleStack indexes.Median length
2,042w
2026-08-0390th percentile 2,998 words.Median quality
44
2026-08-0334.1% name a command; 34.5% contain code.Repositories carrying CLAUDE.md, 2026-08-01 to 2026-08-03
Real CLAUDE.md files
| Repository | Format | Stack | Covers | Score | Changed |
|---|---|---|---|---|---|
| microsoft/playwrightCLAUDE.md · 94k | CLAUDE.md | buildtestlint-formatstyle+7 | 100/100 | 3 days ago | |
| filamentphp/filamentCLAUDE.md · 32k | CLAUDE.md | buildtestlint-formatstyle+7 | 100/100 | 3 days ago | |
| bagisto/bagistoCLAUDE.md · 28k | CLAUDE.md | setupbuildteststyle+5 | 100/100 | 3 days ago | |
| livewire/livewireCLAUDE.md · 24k | CLAUDE.md | setupbuildteststyle+4 | 100/100 | 3 days ago | |
| stacklok/toolhiveCLAUDE.md · 2.0k | CLAUDE.md | buildteststylearch+4 | 100/100 | 3 days ago | |
| nimbalyst/nimbalystpackages/android/CLAUDE.md · 1.4k | CLAUDE.md | setupbuildstylearch+2 | 100/100 | 3 days ago | |
| dotCMS/corecore-web/CLAUDE.md · 950 | CLAUDE.md | teststylearchtesting-strategy+3 | 100/100 | 3 days ago | |
| Adit-Jain-srm/NightmareNetCLAUDE.md · 45 | CLAUDE.md | buildtestlint-formatstyle+6 | 100/100 | 3 days ago | |
| dotCMS/coreCLAUDE.md · 950 | CLAUDE.md | setupbuildteststyle+7 | 99/100 | 3 days ago |
What it asserts
2026-08-02Read from the format’s own documentation and checked by hand. Capabilities are asserted; adoption is measured.
- File
- CLAUDE.md
- When it applies
- Always in scope. Project file, plus nested files in subdirectories, plus a user-level file (~/.claude/CLAUDE.md) that applies across every project.
- Size limits
- None documented
- Tools that read it
- Claude Code
Capabilities
- Read by more than one tool
- Frontmatter
- Glob targeting
- Imports other files
- Nested / per-directory
- Multiple files
- User-level scope
Strengths
- @path imports — shared conventions written once and pulled into each file
- A user-scope file lets personal preferences live outside the team repo
- Nested project files compose with the root file rather than replacing it
Weaknesses
- Single-vendor: no other agent reads it, so multi-tool teams maintain two files
- No glob targeting, same context cost as AGENTS.md — path-scoped rules exist, but in a separate .claude/rules/ file, not in CLAUDE.md itself
Measured — counted from real repositories, nightlyAsserted — read from the vendor docs, dated
Repositories that carry CLAUDE.md and something else
Counted pairwise across the whole corpus. The percentage is of repositories carrying CLAUDE.md — the number a “CLAUDE.md vs …” search is really asking for.
+ AGENTS.md
50.8%
2026-08-03126 repos carry both31.8% the other way
+ Cursor rules22.2%
2026-08-0355 repos carry both30.7% the other way
+ Copilot instructions19.0%
2026-08-0347 repos carry both37.3% the other way
+ Cline rules10.1%
2026-08-0325 repos carry both31.6% the other way
+ GEMINI.md6.9%
2026-08-0317 repos carry both51.5% the other way
+ .cursorrules4.0%
2026-08-0310 repos carry both37.0% the other way
+ Windsurf rules2.8%
2026-08-037 repos carry both50.0% the other way
