vendor-adapters

This is the single source of truth for how harness artifacts map across Claude Code, Cursor, Codex, and GitHub Copilot CLI. Use it when comparing vendor behavior, checking format compatibility, or running a vendor sync update.

Vendor Documentation URLs

Claude Code (Anthropic)

Area	URL
CLI Reference	https://code.claude.com/docs/en/cli-reference
Plugins Overview	https://code.claude.com/docs/en/plugins
Plugins Reference	https://code.claude.com/docs/en/plugins-reference
Plugin Marketplaces	https://code.claude.com/docs/en/plugin-marketplaces
Hooks Guide	https://code.claude.com/docs/en/hooks-guide
MCP Servers	https://code.claude.com/docs/en/mcp
Settings Reference	https://code.claude.com/docs/en/settings
Subagents	https://code.claude.com/docs/en/sub-agents
Official Plugins Repo	https://github.com/anthropics/claude-plugins-official

OpenAI Codex

Area	URL
Plugins Overview	https://developers.openai.com/codex/plugins
Plugin Build Guide	https://developers.openai.com/codex/plugins/build
Hooks	https://developers.openai.com/codex/hooks
CLI Reference	https://developers.openai.com/codex
GitHub Repo	https://github.com/openai/codex
Hook Schemas	https://github.com/openai/codex/tree/main/codex-rs/hooks/schema/generated

Cursor

Area	URL
Plugin Template	https://github.com/cursor/plugin-template
Official Plugins Repo	https://github.com/cursor/plugins
Marketplace	https://cursor.com/marketplace
Plugins Reference	https://cursor.com/docs/reference/plugins
MCP Servers	https://cursor.com/docs/context/mcp
Rules (.mdc)	https://cursor.com/docs/context/rules
Hooks	https://cursor.com/docs/hooks
Subagents	https://cursor.com/docs/subagents
CLI	https://cursor.com/cli
Forum: .agents/ support	https://forum.cursor.com/t/support-for-agent-folder-compatibility/154167

GitHub Copilot CLI

Area	URL
Product Page	https://github.com/features/copilot/cli
About CLI Plugins	https://docs.github.com/en/copilot/concepts/agents/copilot-cli/about-cli-plugins
Creating a Plugin	https://docs.github.com/en/copilot/how-tos/copilot-cli/customize-copilot/plugins-creating
Creating a Marketplace	https://docs.github.com/en/copilot/how-tos/copilot-cli/customize-copilot/plugins-marketplace
Plugin Reference	https://docs.github.com/en/copilot/reference/copilot-cli-reference/cli-plugin-reference
Command Reference	https://docs.github.com/en/copilot/reference/copilot-cli-reference/cli-command-reference
Programmatic Reference	https://docs.github.com/en/copilot/reference/copilot-cli-reference/cli-programmatic-reference
Config Directory Reference	https://docs.github.com/en/copilot/reference/copilot-cli-reference/cli-config-dir-reference
Hooks Reference	https://docs.github.com/en/copilot/reference/hooks-reference
Custom Agents Configuration	https://docs.github.com/en/copilot/reference/custom-agents-configuration
Agent Skills	https://docs.github.com/en/copilot/how-tos/copilot-cli/customize-copilot/add-skills
Custom Instructions	https://docs.github.com/en/copilot/how-tos/copilot-cli/customize-copilot/add-custom-instructions
MCP Servers	https://docs.github.com/en/copilot/how-tos/copilot-cli/customize-copilot/add-mcp-servers
Issue Tracker	https://github.com/github/copilot-cli

Cross-Vendor Standards

Area	URL
Agent Skills	https://agentskills.io
AGENTS.md Spec	https://github.com/agentsmd/agents.md
.agents/ Folder Spec	https://github.com/agentsfolder/spec
MCP Spec	https://modelcontextprotocol.io/specification/2025-03-26
Agent Plugins 1.0 (Open Plugin Spec)	https://github.com/agentplugins/agent-plugins-spec

Vendor Support Matrix

Quick-lookup: what each vendor supports. For format details see references/.

Artifact	Claude Code	Cursor	Codex	Copilot CLI
Skills	✓ full	✓ full	✓ full	✓ full (also reads .claude/skills)
SubAgents	✓ full	✓ full (name+description)	✗ not in plugins	✓ full (agents/*.md or *.agent.md)
MCP	✓ stdio + HTTP	✓ stdio + SSE + OAuth	✓ stdio only	✓ stdio/local + HTTP + SSE
Hooks	✓ ~30 events, 5 types	✓ 21 events, flat format	✓ 11 events, command only	✓ 14 events, 3 types, version: 1
Startup Context	✓ CLAUDE.md + rules/	✓ .cursor/rules/*.mdc	✓ AGENTS.md only	✓ AGENTS.md + CLAUDE.md + copilot-instructions.md
Rules in plugins	✓ .claude/rules/*.md	✓ .mdc with frontmatter	✗ not supported	~ *.instructions.md with applyTo
Commands	✓ legacy (prefer skills)	✓ commands/*.md	✗ not supported	~ manifest field only, format undocumented
LSP	✓ .lsp.json	✗	✗	✓ lsp.json / .github/lsp.json

Manifest and Marketplace Path Resolution

Copilot CLI reads Claude Code's manifest paths as a fallback, which is why a Claude plugin often installs into Copilot unchanged.

Vendor	Plugin manifest	Marketplace index
Claude Code	.claude-plugin/plugin.json	.claude-plugin/marketplace.json
Cursor	.cursor-plugin/plugin.json	.cursor-plugin/marketplace.json
Codex	.codex-plugin/plugin.json	.agents/plugins/marketplace.json
Copilot CLI	.plugin/ → plugin.json → .github/plugin/ → .claude-plugin/	marketplace.json → .plugin/ → .github/plugin/ → .claude-plugin/

Marketplace Source Types — the Claude ↔ Copilot trap

Copilot CLI will read .claude-plugin/marketplace.json, but the two vendors do not accept the same source discriminators. An unrecognised type fails the whole index, not just that entry, so one bad row makes every plugin in the marketplace uninstallable from Copilot.

source type	Claude Code	Copilot CLI (tested, v1.0.80)
relative path string	✓	✓
github object	✓ (no path)	✓ (supports path)
url object	✓ (no path)	✓
git-subdir object	✓ (only Claude type with path)	✗ rejected — fails whole file
npm object	✓	✗ rejected
archive object	✓	✗ rejected
command object	✓	✗ rejected

Copilot accepts exactly three: relative path, github, url.

Plugin names must be kebab-case for Copilot; a dot (e.g. wordpress.com) also fails the whole index unless the plugin opts into Open Plugin Spec via $schema.

Portable choice: relative paths. For a git subdirectory, Copilot wants {"source": "github", "repo": "o/r", "path": "sub/dir"} (or the OWNER/REPO:PATH install string) while Claude wants {"source": "git-subdir", "url": …, "path": …} — no single row satisfies both, so publish a Copilot-safe .github/plugin/marketplace.json alongside the Claude one.

See references/copilot.md for the full detail and the upstream issues.

Format Mapping Tables

(See references/ directory for full format details — anthropic.md, cursor.md, codex.md, copilot.md)

Known Gaps

All gaps live in one table: references/known-gaps.md. Each gap entry:

• Priority: HIGH / MED / LOW
• Description: what's wrong or missing
• Vendor: which vendor
• Status: OPEN / RESOLVED / MITIGATED / WITHDRAWN (with a dated note)

Update Workflow

When vendor documentation changes:

1. Use fetch-vendor-docs skill to retrieve current docs from URLs above
2. Compare against stored references in this skill's references/ directory
3. Identify: what changed, what's new, what was removed
4. Update affected reference files
5. Use flag-vendor-gaps skill to update gap table