Plugins & Marketplaces

Install reusable skill packs from catalogs — same name@marketplace shape as Claude Code / Grok Build.

MVP scope: plugins contribute skills (loaded into the agent catalog). MCP/hooks/agents inside plugins are not wired yet.

Marketplaces are cloned with git, so git must be installed and in PATH (on Windows: Git for Windows — which cast's bash tool wants anyway). Without it, marketplace commands fail with an explicit message rather than a raw spawn error.

Quick start

Three catalogs are always registered and can't be removed:

Label	Source
Codex	`openai/plugins`
Claude	`anthropics/claude-plugins-official`
Grok	`xai-org/plugin-marketplace`

They're seeded on first use of /plugin (a cheap check after that — no re-cloning). Browse and install straight away:

/plugin marketplace list
/plugin marketplace list xai-official
/plugin install superpowers@xai-official
/skills

Add your own catalog alongside the defaults:

/plugin marketplace add owner/repo        # GitHub shorthand
/plugin marketplace add https://...       # any git URL
/plugin marketplace add ./my-marketplace  # local path (testing / private plugins)

Only marketplaces you added yourself can be removed with /plugin marketplace remove <name> — the three defaults reject removal.

Hot-reload

/plugin install, uninstall, enable / disable, bare /plugin toggle, and marketplace remove reload the skill catalog in the current session. No /reload and no new session.

/reload is only for skills/rules/MCP/personas you added or edited as files outside these commands. See Interactive commands.

Commands

Type /plugin in the composer — the palette lists every subcommand (install, marketplace list, …) with a short hint. Pick a row, then fill args if needed.

Command	What it does
`/plugin`	Toggle installed plugins on/off (same picker UX as `/mcp` / `/skills`)
`/plugin install <name>@<marketplace>`	Fetch plugin, enable it, reload skills
`/plugin uninstall`	Interactive: pick installed plugin, confirm, remove
`/plugin uninstall <name>@<marketplace>`	Remove by ref (no picker)
`/plugin enable` / `disable <name>@<marketplace>`	Toggle one plugin without the picker
`/plugin list`	Installed plugins (text list)
`/plugin marketplace add <owner/repo\|url\|path>`	Register a catalog
`/plugin marketplace list [name]`	Known catalogs, or plugins in one
`/plugin marketplace update <name>`	`git pull` / refresh checkout
`/plugin marketplace remove <name>`	Drop catalog, installs, `enabledPlugins` keys; reload skills

Layout on disk

~/.cast/plugins/
  known_marketplaces.json
  installed.json
  marketplaces/<name>/          # catalog checkout
  installs/<marketplace>/<plugin>/

Enabled state is stored in ~/.cast/settings.json under enabledPlugins ("name@marketplace": true|false).

Marketplace format

Cast reads any of:

.cast-plugin/marketplace.json
.grok-plugin/marketplace.json
.claude-plugin/marketplace.json

Compatible with Grok/Claude entries: relative ./plugins/foo, { "source": "url", "url", "sha", "path" }, { "source": "git-subdir", … }, { "type": "local", "path" }.

Skill discovery from a plugin

If <pluginRoot>/skills/ exists → load that directory
Else → load <pluginRoot> itself (skill-only repos)

Priority vs other skills: project > global > plugin > builtin > --skill paths.

A pack may contribute several skills; each is labeled with plugin · name@marketplace in /skills. Disabling a pack with /plugin keeps those skills visible but locked until the pack is re-enabled — they leave the agent catalog immediately.

On a name collision between two enabled plugins, the first id in sorted name@marketplace order wins.

--no-skills skips plugin skill dirs as well (same as project/global/builtin); --skill paths still load.