Plugins and marketplaces in Claude Code, Codex and Cursor

A coding-agent plugin is a versioned bundle of skills, slash commands, subagents, hooks and MCP servers that Claude Code, Codex, Cursor and GitHub Copilot CLI install from a marketplace: a git repository with a catalogue file. Install commands differ per agent, and every plugin adds context cost worth measuring before a team adopts it.

A teammate says “install the Vercel plugin”. You type claude plugin add vercel and get unknown command 'add'. Once installed, it adds about 4,217 tokens to every session (claude plugin details vercel, Claude Code 2.1.283), and your teammate has a different set. This page is for developers who install plugins and tech leads who choose them.

What this plugins overview gives you

• One command table for four agents, with the spellings that fail
• One plugin installed, measured and removed in each agent
• A four-step adoption workflow (evaluate, measure, pin, review)
• Managed settings that restrict a team to approved marketplaces

Plugin, skill or MCP server: which one do you need?

A skill is one SKILL.md folder of instructions. An MCP server is a live connection to a tool or data source. A plugin packages several of these, plus hooks and subagents, under one version.

You need	Reach for
A reusable procedure, such as a release checklist	A skill
Live access to GitHub or a database	An MCP server
A skill, a hook and a server that work together	A plugin
One bundle, one version, on every laptop	A plugin from a marketplace

The ecosystem overview shows the other layers.

Plugin commands in Claude Code, Codex, Cursor and Copilot CLI

Checked on 2026-09-26 against Claude Code 2.1.283, codex-cli 0.157.1 and Copilot CLI 1.0.88; the Cursor column comes from Cursor’s cursor/plugins repository.

Task	Claude Code	Codex	Cursor	Copilot CLI
Add a marketplace	claude plugin marketplace add owner/repo	codex plugin marketplace add owner/repo	not verified (team marketplaces: Dashboard → Settings → Plugins, secondary)	copilot plugin marketplace add owner/repo
Install	claude plugin install NAME@MKT	codex plugin add NAME@MKT	/add-plugin NAME in Agent chat, or Cursor Settings → Plugins	copilot plugin install NAME@MKT
List	claude plugin list	codex plugin list	not verified	copilot plugin list
Measure context cost	claude plugin details NAME	no command	not verified	no command
Update a plugin	claude plugin update NAME@MKT	no update subcommand (0.157.1); how an installed plugin gets a new version is not verified	not verified	copilot plugin update --all
Refresh marketplaces	claude plugin marketplace update	codex plugin marketplace upgrade	not verified	copilot plugin marketplace update
Disable	claude plugin disable NAME@MKT	enabled = false in config.toml	not verified	copilot plugin disable NAME
Uninstall	claude plugin uninstall NAME@MKT	codex plugin remove NAME@MKT	not verified	copilot plugin uninstall NAME
In-session browser	/plugin	/plugins	not verified	/plugin (per README, not run)

Spellings that fail

claude plugin add and codex plugin install are unknown commands. Codex uses upgrade where Claude Code and Copilot CLI use update. The name after @ is the marketplace’s name field, not the repository. In Claude Code, plugin skills are namespaced, so /code-review is the built-in reviewer and /code-review:code-review is the plugin.

How each tool’s marketplace works

• Claude Code registers claude-plugins-official on first start; /reload-plugins applies changes without a restart.
• Codex ships openai-curated and also reads Claude-format marketplaces.
• Cursor reads a .cursor-plugin/plugin.json manifest.
• Copilot CLI has awesome-copilot and copilot-plugins built in.

On claude.com/plugins on 2026-09-26, the most-installed plugins were Frontend Design (1,134,112 installs) and Superpowers (1,009,371); marketplaces and registries compares the catalogues.

Install, measure, disable and remove one plugin in each agent

Trail of Bits’ differential-review plugin lives in a Claude-format marketplace that Claude Code, Codex and Copilot CLI accept.

Claude Code

claude plugin marketplace add trailofbits/skills
claude plugin install differential-review@trailofbits
claude plugin details differential-review

details prints the inventory and per-session cost:

Component inventory
  Skills (2)  diff-review, differential-review
  Agents (1)  adversarial-modeler
Projected token cost
  Always-on:   ~258 tok   added to every session

Run it in a session as /differential-review:diff-review. Then turn it off or remove it:

claude plugin disable differential-review@trailofbits
claude plugin uninstall differential-review@trailofbits

Codex

codex plugin marketplace add trailofbits/skills
codex plugin add differential-review@trailofbits
codex plugin list        # differential-review@trailofbits  installed, enabled  1.1.4
codex plugin remove differential-review@trailofbits

Codex has no cost report; to disable without removing, see the table above.

Cursor

In Cursor Settings → Plugins, search for Playwright and click Install, or type /add-plugin playwright in chat (per its README in cursor/plugins). It starts npx -y @playwright/mcp@latest, so Node.js must be on PATH. Cost, disable and uninstall controls were not verified on 2026-09-26.

How a team adopts a plugin: evaluate, measure, pin, review

1. Evaluate the source. Hooks and MCP servers run with your credentials; read the source first.

   Copy-paste prompt: audit a plugin before install

   Clone https://github.com/trailofbits/skills into /tmp/plugin-audit and inspect the plugin at plugins/differential-review. Do not install or run anything. Report: every hook (event and the command it runs), every MCP server (command or URL, and the environment variables it reads), any script that makes network calls, and which files load into context on every session. End with a verdict: safe to trial, needs changes, or reject, with the file and line behind each concern.

2. Measure the cost. Run claude plugin details NAME, then /context in a session, because MCP tool schemas are not in that figure (cut MCP token cost). Our rule of thumb: above about 2,000 always-on tokens, use project scope, never user scope.

3. Pin it to the project. claude plugin install differential-review@trailofbits --scope project writes the plugin into .claude/settings.json:

   { "enabledPlugins": { "differential-review@trailofbits": true } }

   Add the marketplace with --scope project too. In Codex, pin the marketplace to a tag with codex plugin marketplace add owner/repo --ref TAG.

4. Review it like code. The settings change goes through a pull request the allowlist owner signs off. If the plugin ships evals/, claude plugin eval NAME@MKT scores it against a no-plugin baseline.

   Replace the placeholder path in this prompt with your own approved-marketplace list.

   Copy-paste prompt: review a plugin change in a PR

   This PR changes enabledPlugins or extraKnownMarketplaces in .claude/settings.json. For each added or updated plugin, run `claude plugin details <name>` and report always-on tokens, hooks and MCP servers. Flag any plugin over 2,000 always-on tokens, any marketplace outside the approved list in <path to your approved-marketplace list>, and any skill that duplicates one already in .claude/skills/. Post the findings as a table; do not approve the PR.

How to allowlist marketplaces for the whole team

In Claude Code, managed settings restrict which marketplaces anyone can add and pre-enable approved plugins:

{
  "strictKnownMarketplaces": [
    { "source": "github", "repo": "acme/*" }
  ],
  "enabledPlugins": { "acme-review@acme-plugins": true }
}

Build a plugin or a private marketplace covers hosting the team catalogue.

Codex (a [marketplaces] table in managed requirements.toml, checked at rust-v0.157.1) and Cursor (Team Marketplaces) are compared in one policy for every coding agent.

What goes wrong with plugins, and how to recover

• A pushed fix never reaches teammates. Updates wait for a version bump in plugin.json, and third-party marketplaces do not auto-update. Run claude plugin marketplace update, then claude plugin update NAME@MKT, and restart.
• A committed plugin is missing on a teammate’s machine. A plugin with an external source still needs claude plugin install NAME@MKT --scope project once per machine.
• A private marketplace fails to clone. Claude Code never prompts for credentials; run gh auth login and gh auth setup-git.

Where to go next with plugins

The plugins worth installing Ranked catalogue with install counts and context cost.

Build a plugin or a private marketplace Manifests, versioning, validate --strict in CI and a team marketplace.

Marketplaces and registries Where plugins come from and how far to trust each channel.

Skill supply-chain security What to check before third-party instructions enter your agent's context.