GEMINI.md vs Windsurf rules vs Cline 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.

Measured — counted from real repositories, nightlyAsserted — read from the vendor docs, dated

CompareAGENTS.md CLAUDE.md Cursor rules Copilot instructions Cline rules GEMINI.md .cursorrules Windsurf rulestwo to five

Format	GEMINI.md 2026-08-01	Windsurf rules 2026-08-01	Cline rules 2026-08-01
Asserted — what the docs say it can express
File	GEMINI.md	.windsurf/rules/*.md	.clinerules
Status	vendor	vendor	vendor
Cross-tool	No	No	No
Tools that read it	Gemini CLI Gemini Code Assist	Windsurf Cascade	Cline Roo Code
Frontmatter	No	Yes	No
Glob targeting	No	Yes	No
Imports other files	Yes	No	No
Nested / per-directory	Yes	No	No
Multiple files	Yes	Yes	Yes
User-level scope	Yes	Yes	Yes
When it applies	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.	Always in scope. Either a single .clinerules file or a .clinerules/ directory whose markdown files are all loaded.
Size limits	None	Per-rule and total character caps apply; long rules are truncated rather than rejected.	None
Measured — counted from real repositories on 2026-08-04
Repositories carrying it	33	14	79
Share of indexed repos	4.7%	2.0%	11.3%
Files indexed	46	102	305
Median length (words)	257	515	262
90th percentile length	1,704	1,518	1,412
Files naming commands	52.2%	37.3%	34.1%
Files containing code	45.6%	70.6%	33.1%
Median quality score	60	58	54
Median repository stars	11,320	119	1

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.

Windsurf rules + Cline rules

2026-08-04

repositories carry both. That is 57.1% of everything with Windsurf rules, and 10.1% of everything with Cline rules.

GEMINI.md + Windsurf rules

2026-08-04

repositories carry both. That is 21.2% of everything with GEMINI.md, and 50.0% of everything with Windsurf rules.

GEMINI.md + Cline rules

2026-08-04

repositories carry both. That is 21.2% of everything with GEMINI.md, and 8.9% of everything with Cline rules.

What each one is for

GEMINI.md

2026-08-01

Gemini 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

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Windsurf rules

2026-08-01

Cursor'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

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Cline rules

2026-08-01

A single file or a folder of files, all always-on. The folder form is the simplest way any format here lets you split rules into topics without also learning an activation model.

Strengths

Directory form splits rules by topic with zero configuration
Toggleable rule sets for switching context between tasks

Weaknesses

Cline-only
Everything is always-on — no targeting, so the folder form costs context

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