| name | startup-context |
| description | Validate and diagnose startup context files — CLAUDE.md, AGENTS.md, rules, and .cursorrules — that inject instructions into the model context at session start across Claude Code, Cursor, and Codex. |
Use this skill when working with files that inject instructions at startup — validating format, diagnosing why instructions aren't being read, or understanding load order and precedence per vendor.
What startup context is: Files that are automatically loaded into the model's context before any user prompt. Each vendor uses different file names and locations. All serve the same purpose: priming the model with project-specific or harness-level instructions.
Vendor mapping:
| Vendor | Primary file | Rules format | Legacy |
|---|
| Claude Code | CLAUDE.md | .claude/rules/*.md | — |
| Cursor | .cursor/rules/*.mdc | .cursor/rules/*.mdc | .cursorrules (root) |
| Codex | AGENTS.md | NOT SUPPORTED in plugins | — |
Load order (Claude Code): User CLAUDE.md (~/.claude/CLAUDE.md) → Project CLAUDE.md → Plugin CLAUDE.md (via @-import). Rules in .claude/rules/ are loaded after CLAUDE.md.
The @AGENTS.md workaround (Claude Code): Claude Code does not natively read AGENTS.md. When ynh exports for Claude, it writes a CLAUDE.md containing only @AGENTS.md — using Claude's @-import syntax to pull in the cross-vendor instructions file without duplicating content.
Diagnostic checklist:
- Is the file in the right location for the vendor?
- Claude Code: does the plugin CLAUDE.md use @-import correctly?
- Cursor: is the rules file .mdc (not .md)? Does it have required frontmatter (description, globs, alwaysApply)?
- Codex: rules are not supported in plugin format — use AGENTS.md only
- Check file encoding and line endings — bare CR can cause silent failures
