Project-level instructions
Repo-specific guidance files checked into version control (e.g. CLAUDE.md, .cursorrules, copilot-instructions.md)
Baseline Widely available Fully supported by every tracked agent since Jan 2026, when GitHub Copilot added it. Based on web.dev's Baseline
Scope Instructions
Supported
Partial
No
Unknown
Not released
Claude Code Current · Oct 2026 
Codex Current · Oct 2026 
GitHub Copilot Current · Oct 2026 
Cursor Current · Oct 2026 
OpenCode Current · Oct 2026 0.2.31 - 2.1.311
0.2.0 - 0.164.0
0.0.374 - 1.0.103
0.45 - 3.27
0.1.30 - 1.19.4
Supported by all 5 agents.
HoverTap any cell for version details.