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Cross-Agent Compatibility

This marketplace keeps Claude Code support while adding documented registration paths for Codex and GitHub Copilot CLI.

Shared Instructions

Use AGENTS.md as the shared source of truth for repository instructions. Codex reads AGENTS.md before work and layers global, project, and nested instructions by directory precedence. GitHub Copilot supports repository agent instructions through AGENTS.md; Copilot cloud agent also supports root CLAUDE.md and GEMINI.md.

CLAUDE.md should remain a Claude Code adapter:

@AGENTS.md

## Claude Code Specific Instructions

Append Claude-only plugin, skill, command, or MCP guidance here.

Claude Code

Claude Code uses the existing marketplace manifest:

claude plugin marketplace add neuromechanist/research-skills
claude plugin install project@research-skills

The canonical Claude marketplace file remains .claude-plugin/marketplace.json.

Codex

Codex supports repository marketplaces at .agents/plugins/marketplace.json and legacy-compatible marketplaces at .claude-plugin/marketplace.json. This repo includes the native .agents/plugins/marketplace.json so a checkout can be used directly as a Codex marketplace root:

codex plugin marketplace add neuromechanist/research-skills
codex plugin marketplace add ./path/to/research-skills

Codex skills are directories containing SKILL.md files with name and description frontmatter. The native .codex-plugin/plugin.json manifests point at the existing plugins/<name>/skills/ trees. Claude-specific commands and agents stay declared in the .claude-plugin/plugin.json manifests; Copilot agent templates are exposed through native .github/plugin/plugin.json manifests.

Codex custom subagents are separate from plugin skills. Current Codex docs define custom agents as standalone TOML files under ~/.codex/agents/ for personal scope or .codex/agents/ for project scope, with required name, description, and developer_instructions fields. Codex only spawns subagents when explicitly asked, and /agent is used in the CLI to inspect or switch active agent threads. For review/QA surfaces in this marketplace, keep agents/templates/*.toml as opt-in Codex custom-agent templates; installing the plugin exposes the skill, not the subagent.

GitHub Copilot CLI

Copilot CLI supports marketplaces through .github/plugin/marketplace.json and also looks for .claude-plugin/marketplace.json. This repo includes .github/plugin/marketplace.json for the native Copilot path:

copilot plugin marketplace add neuromechanist/research-skills
copilot plugin marketplace browse research-skills
copilot plugin install project@research-skills

Copilot CLI plugin manifests support component path fields including skills, commands, and agents; agents points to directories containing .agent.md files. Every plugin in this repo now has a native per-plugin .github/plugin/plugin.json manifest. Plugins with review/QA agents expose agents/templates/ as the Copilot agents component path. The agents/*.md files remain Claude Code agent shells; agents/templates/*.agent.md are the Copilot custom-agent files.

Copilot custom-agent files use YAML frontmatter where description is required and the Markdown body defines the agent behavior. Optional frontmatter includes name, tools, model, target, disable-model-invocation, and user-invocable. Keep review/QA agent descriptions scoped to "invoked by the <skill> skill" so the skill remains the cross-agent trigger owner.

Sources

  • OpenAI Codex AGENTS.md guide: https://developers.openai.com/codex/guides/agents-md
  • OpenAI Codex plugin build guide: https://developers.openai.com/codex/plugins/build
  • OpenAI Codex skills guide: https://developers.openai.com/codex/skills
  • OpenAI Codex subagents guide: https://developers.openai.com/codex/subagents
  • GitHub Copilot repository instructions: https://docs.github.com/en/copilot/how-tos/copilot-on-github/customize-copilot/add-custom-instructions/add-repository-instructions
  • GitHub Copilot custom instructions support: https://docs.github.com/en/copilot/reference/custom-instructions-support
  • GitHub Copilot custom agents configuration: https://docs.github.com/en/copilot/reference/custom-agents-configuration
  • GitHub Copilot CLI plugin reference: https://docs.github.com/en/copilot/reference/copilot-cli-reference/cli-plugin-reference