CLAUDE.md vs GEMINI.md vs Windsurf rules
Every comparison page on the web is a capability table someone wrote from the vendor docs in an afternoon. None of them can tell you how many real repositories ship each file, how long the median one runs, or how often two of them turn up in the same project. Those answers need a corpus, and RuleStack counts one every night.
| Format | CLAUDE.md 2026-08-02 | GEMINI.md 2026-08-01 | Windsurf rules 2026-08-01 |
|---|---|---|---|
| Asserted — what the docs say it can express | |||
| File | CLAUDE.md | GEMINI.md | .windsurf/rules/*.md |
| Status | vendor | vendor | vendor |
| Cross-tool | No | No | No |
| Tools that read it |
|
|
|
| Frontmatter | No | No | Yes |
| Glob targeting | No | No | Yes |
| Imports other files | Yes | Yes | No |
| Nested / per-directory | Yes | Yes | No |
| Multiple files | Yes | Yes | Yes |
| User-level scope | Yes | Yes | Yes |
| 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. | Hierarchical memory: a global ~/.gemini/GEMINI.md, then the project file, then nested files, concatenated from broadest to narrowest. | Four trigger modes in frontmatter: always_on, glob, model_decision, manual. The legacy single-file .windsurfrules is still read. |
| Size limits | None | None | Per-rule and total character caps apply; long rules are truncated rather than rejected. |
| Measured — counted from real repositories on 2026-08-04 | |||
| Repositories carrying it | 248 | 33 | 14 |
| Share of indexed repos | 35.5% | 4.7% | 2.0% |
| Files indexed | 775 | 46 | 102 |
| Median length (words) | 2,042 | 257 | 515 |
| 90th percentile length | 2,998 | 1,704 | 1,518 |
| Files naming commands | 34.2% | 52.2% | 37.3% |
| Files containing code | 34.5% | 45.6% | 70.6% |
| Median quality score | 44 | 60 | 58 |
| Median repository stars | 114 | 11,320 | 119 |
How often they turn up together
A capability table cannot answer this at all. Of the repositories carrying the first format, this is the share that also carry the second — counted, both directions, on 2026-08-04.
GEMINI.md + Windsurf rules
2026-08-047
repositories carry both. That is 21.2% of everything with GEMINI.md, and 50.0% of everything with Windsurf rules.
CLAUDE.md + Windsurf rules
2026-08-047
repositories carry both. That is 2.8% of everything with CLAUDE.md, and 50.0% of everything with Windsurf rules.
CLAUDE.md + GEMINI.md
2026-08-0417
repositories carry both. That is 6.9% of everything with CLAUDE.md, and 51.5% of everything with GEMINI.md.
What each one is for
CLAUDE.md
2026-08-02Claude 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.
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
GEMINI.md
2026-08-01Gemini CLI's memory file, structurally close to CLAUDE.md — @imports and a user-scope layer — which is why repos that carry both usually carry near-identical text in each.
Strengths
- @path imports and a global user file, same composition model as CLAUDE.md
- Explicit hierarchy from global to local
Weaknesses
- Google-only
- No glob targeting
Windsurf rules
2026-08-01Cursor's activation model with a different vocabulary — trigger modes instead of rule types — plus hard character caps, which is the one place a format here will silently drop instructions rather than fail loudly.
Strengths
- Trigger modes give the same glob and on-demand targeting as Cursor rules
- Workspace and global rule scopes
Weaknesses
- Windsurf-only
- Character caps truncate silently — a long rule can be half-applied with no error
- No imports
