IDE rules for Claude Code, Codex and Cursor
Cursor rules, Copilot instructions, Windsurf rules and AGENTS.md: what the agent keeps in every request.
Nothing here yet: cards appear once a checked description is ready.
A rule is an instruction the agent receives with every request, or whenever it touches matching files: the project stack, build commands, things it must not do, code style. Plain Markdown, sometimes with frontmatter.
Almost every platform has its own file. Claude Code reads CLAUDE.md and .claude/rules/*.md with a paths field. Cursor keeps rules in .cursor/rules/*.mdc with description, globs and alwaysApply, and still reads the legacy .cursorrules. Copilot uses .github/copilot-instructions.md plus *.instructions.md with applyTo; Windsurf (Devin Desktop) has .devin/rules/, Kiro has .kiro/steering/.
The closest thing to a shared format is AGENTS.md. Codex, Cursor, Copilot, Kiro, OpenCode and Zed read it, Gemini CLI does after a settings change, and Claude Code does since version 2.1.277 when the project has no CLAUDE.md. Anthropic suggests keeping each CLAUDE.md under 200 lines. More: Cursor rules, AGENTS.md vs CLAUDE.md.
