Where the file goes

The generated rules do not name a vendor. The filename does.

Save asPut itRead by
AGENTS.mdproject rootCursor, Codex, Copilot, Jules, others. agents.md
CLAUDE.mdproject root, or ~/.claude/CLAUDE.mdClaude Code. docs
bothAGENTS.md plus a CLAUDE.md containing @AGENTS.mdOne source, two readers
GEMINI.mdproject rootGemini CLI
copilot-instructions.md.github/GitHub Copilot
.windsurfrulesproject rootWindsurf
.clinerulesproject rootCline
Customwhatever that tool actually readsYou

Paste into a settings or custom-instructions field when there is no file. Same content either way.

Cursor: save AGENTS.md in the project you have open. Nested folders can override a root file — the nearest one wins.