Author, scaffold, or edit a plugin once in Claude Code format, then generate the Codex, Antigravity, and Cursor manifests so one directory loads in all four runtimes. Use when creating/scaffolding a new plugin, editing a plugin or its manifest, wiring a marketplace entry, running the multi-format generator, or when the user mentions "plugin.json", ".claude-plugin", ".codex-plugin", ".cursor-plugin", "multi-format", "marketplace.json", "scaffold a plugin", or "Codex/Cursor/Antigravity plugin".
Installation
Install with Codex or Claude Copy this prompt, paste it into Codex, Claude, or another assistant, and let it review the skill page and install it for you.
Author, scaffold, or edit a plugin once in Claude Code format, then generate the Codex, Antigravity, and Cursor manifests so one directory loads in all four runtimes. Use when creating/scaffolding a new plugin, editing a plugin or its manifest, wiring a marketplace entry, running the multi-format generator, or when the user mentions "plugin.json", ".claude-plugin", ".codex-plugin", ".cursor-plugin", "multi-format", "marketplace.json", "scaffold a plugin", or "Codex/Cursor/Antigravity plugin".
Plugin Authoring — Multi-Runtime
This marketplace ships the same plugin directory across four runtimes. You author once in
Claude Code format (the source of truth) and generate the rest. Never hand-write the Codex,
Antigravity, or Cursor manifests.
Scaffold / edit the plugin in Claude Code format. Components go at the plugin root, never
inside .claude-plugin/:
plugins/<name>/
├── .claude-plugin/plugin.json # manifest only (source of truth)
├── commands/ agents/ skills/ # at root, auto-discovered
└── hooks/hooks.json # at root
Author the manifest from references/plugin-json-spec.md — start with valid defaults, no
[TODO: ...] placeholders. Prefer skills over SessionStart hooks (they load only when
relevant). Full quality checklist: references/best-practices.md.
Register in .claude-plugin/marketplace.json (source: "./plugins/<name>"). Claude-only
fields like relevance live only here. For a new plugin, wire the companion files
(release-please, README) too — see references/multi-runtime-manifests.md.
Generate the other runtimes:
bun scripts/cli.ts multi-format
The generator is bundled in this plugin (scripts/run.ts + scripts/multi-format.ts). Details,
the per-runtime mapping table, and the $schema each manifest carries:
references/multi-runtime-manifests.md.
Scope the diff — the generator rewrites all local plugins; git restore any unrelated
churn so the commit stays atomic.
Validate — claude plugin validate plugins/<name>; deeper audit via the validating-plugins
skill.
Manifest location
Every local plugin's Claude source is .claude-plugin/plugin.json; the root plugin.json is the
generated Antigravity manifest. Edit the .claude-plugin/ file — never the root one — then
re-run multi-format.
References (load on demand)
references/plugin-json-spec.md — manifest + marketplace field guide with canonical samples.
references/multi-runtime-manifests.md — per-runtime mapping, the generator, diff scoping.
