Build a Plugin

Build a plugin when an integration needs a reviewed manifest for provider domains, credentials, OAuth, MCP endpoints, runtime dependencies, or bundled provider skills.

Use local app/plugins while iterating in one app. Publish an npm package when more than one app or team should use the integration.

Package layout

Use the same shape locally and in packages:

Plugin package

my-junior-plugin/
├── package.json
├── plugin.yaml
└── skills/
    └── my-provider/
        └── SKILL.md

The package must include the manifest and skills in package.json:

package.json

{
  "name": "@acme/junior-my-provider",
  "type": "module",
  "files": ["plugin.yaml", "skills"]
}

Minimal manifest

A plugin can be manifest-only:

plugin.yaml

name: my-provider
description: Internal workflow bundles

Add credential, MCP, API header, command env, and runtime dependency declarations only when the provider needs them.

Provider manifest

Provider integrations should declare the authority surface in the manifest instead of hiding it in skill instructions:

plugin.yaml

name: my-provider
description: My provider integration

credentials:
  type: oauth-bearer
  domains:
    - api.my-provider.example
  auth-token-env: MY_PROVIDER_AUTH_TOKEN
  auth-token-placeholder: host_managed_credential

oauth:
  client-id-env: MY_PROVIDER_CLIENT_ID
  client-secret-env: MY_PROVIDER_CLIENT_SECRET
  authorize-endpoint: https://my-provider.example/oauth/authorize
  token-endpoint: https://my-provider.example/oauth/token

mcp:
  url: https://api.my-provider.example/mcp

This lets Junior validate and load the provider surface before a turn starts. Bundled skills are discovered from the package skills/ directory; they are not listed inside plugin.yaml.

Runtime dependencies

If a skill needs a CLI or system package inside the sandbox, declare that in plugin.yaml:

plugin.yaml

runtime-dependencies:
  - type: npm
    package: my-provider-cli
    version: 1.2.3

runtime-postinstall:
  - cmd: my-provider-cli
    args: ["install-assets"]

Junior merges runtime dependency declarations from all loaded plugins and prepares them with junior snapshot create.

Register the package

Install the plugin next to @sentry/junior, then list it in juniorNitro:

nitro.config.ts

import { defineConfig } from "nitro";
import { juniorNitro } from "@sentry/junior/nitro";

export default defineConfig({
  modules: [
    juniorNitro({
      plugins: {
        packages: ["@acme/junior-my-provider"],
      },
    }),
  ],
});

Do not use the removed pluginPackages option. junior check rejects it.

Validate

Run validation before deploy:

pnpm exec junior check
pnpm exec junior snapshot create

junior check validates manifest and skill structure. junior snapshot create verifies runtime dependency snapshot inputs when your plugin declares them.

Next step

Use Plugins for packaged plugin registration, then verify auth behavior with Plugin Auth & Context.