Guren Plugin Authoring Skill

You help with two distinct tasks: installing an existing plugin into this app, and authoring a new plugin package. Figure out which one the user wants before acting — they are different workflows.

Full reference: docs/en/guides/plugins.md (or docs/ja/guides/plugins.md) and contributing/plugin-contract.md in the Guren framework repo. This skill is a condensed, task-oriented version for AI agents.

Installing an Existing Plugin

Official (@guren/plugin-*) or community (guren-plugin-*) plugins install with one command, run from the app root:

bunx guren plugin <package-name>

This installs the dependency (bun add, unless --no-install), verifies the plugin's declared gurenPlugin.compatibility against the installed @guren/core (throws unless --ignore-compatibility), registers the provider import in createApp({ providers }) inside src/app.ts, and applies any env/publishes entries the plugin declares. --force overwrites already-published files.

Do not hand-edit src/app.ts to add a plugin provider — always run the command. It's idempotent (safe to re-run) and keeps the import/registration correctly formatted.

If the plugin's manifest omits provider (common for definePlugin()-based plugins, which need configuration), the command will NOT auto-register it — it prints a reminder instead. In that case, add the import and call manually:

// src/app.ts
import { somePlugin } from 'guren-plugin-something'

export const app = createApp({
  // oxlint-disable-next-line guren/no-unvalidated-env-read -- plugin options are built before createApp() parses the environment
  providers: [somePlugin({ apiKey: process.env.SOME_API_KEY! })],
})

Authoring a New Plugin

A Guren plugin is a separate npm package — scaffold it outside the current app directory (a sibling directory, not app/ or src/).

1. Package setup

mkdir guren-plugin-<name> && cd guren-plugin-<name> && bun init

{
  "name": "guren-plugin-<name>",
  "version": "0.1.0",
  "type": "module",
  "main": "dist/index.mjs",
  "types": "dist/index.d.mts",
  "gurenPlugin": { "compatibility": ">=1.0.0" },
  "peerDependencies": { "@guren/core": ">=1.0.0" },
  "devDependencies": {
    "@guren/core": "^1.0.0",
    "@guren/testing": "^1.0.0",
    "typescript": "^5.0.0",
    "tsdown": "^0.22.0"
  }
}

@guren/core is a peer dependency (the host app provides it), and also a dev dependency (for building/testing this package in isolation).

2. Define the plugin with definePlugin()

This is the recommended path for any plugin that needs configuration. Each factory call produces an independent provider — never store config on a static class property (it would leak across registrations):

// src/plugin.ts
import { definePlugin } from '@guren/core'

export interface MyConfig {
  apiKey: string
}

export const myPlugin = definePlugin<MyConfig>({
  name: 'my-plugin',
  register(container, config) {
    container.singleton('my-service', () => new MyClient(config))
  },
  boot(container) {
    // optional: runs after all providers have registered
  },
  // optional: defer instantiation until 'my-service' is first resolved
  // deferred: true,
  // provides: ['my-service'],
})

For plugins needing no configuration or full class-based lifecycle control, export a ServiceProvider subclass directly instead — that contract is unchanged. What plugins may touch: the DI container (this.container / the container passed to definePlugin) and, from boot(), the shared Hono instance via container.make('hono') for middleware. Never reach into framework internals via deep imports (e.g. @guren/<package>/src/...) — only import from public package entry points.

Export it: export { myPlugin } from './plugin'.

3. The gurenPlugin manifest (package.json)

Every field is optional except the parent key itself:

Field	Purpose
compatibility	Semver range of Guren versions this plugin supports (e.g. ">=1.0.0 <2.0.0" — always bound the upper end to the major you've actually tested, don't leave it open-ended). Checked by bunx guren plugin at install time and by bunx guren doctor.
provider	Named class export for bunx guren plugin to auto-register. Omit for definePlugin() factories — those need configuration, so they're always registered manually.
env	Array of { key, value?, comment? } — appended to the installing app's .env.example (and .env if present).
publishes	Array of { from, to } — files copied from this package into the app at install time. to must resolve inside config/, db/migrations/, or resources/; existing files are never overwritten without --force.
commands	{ entry, names } — CLI commands this plugin contributes (see below).

The manifest is pure data — installers never execute plugin code from it.

4. Optional: contribute a guren CLI command

{ "gurenPlugin": { "commands": { "entry": "./dist/commands.mjs", "names": ["my-plugin:sync"] } } }

// src/commands.ts
import { defineCommand } from 'citty'

export default {
  'my-plugin:sync': defineCommand({
    meta: { name: 'my-plugin:sync', description: 'Sync something' },
    async run() { /* ... */ },
  }),
}

Command names must contain a : namespace. Built-in guren commands always win a name collision; a name declared by two installed plugins is dropped for both with a warning. The entry module is imported lazily (only when the command runs or renders its own --help) — never for the root guren --help listing.

5. Test with @guren/testing

import { describe, test, expect } from 'bun:test'
import { createPluginTestApp, assertPluginRegisters } from '@guren/testing'
import { myPlugin } from './plugin'

test('registers the service', async () => {
  const app = await createPluginTestApp([myPlugin({ apiKey: 'test' })])
  assertPluginRegisters(app, ['my-service'])
})

6. Test locally before publishing

# from the app you're testing against
bun add file:../guren-plugin-<name>
bunx guren plugin guren-plugin-<name>

bun add file: (and link:/workspace:) symlink back to the plugin's source instead of copying it. If the plugin still has its own node_modules (from its @guren/core devDependency in step 1), the app can load two separate @guren/core copies — surfacing as duplicate-module runtime warnings or a Property 'bindings' is protected... TypeScript error. Fix: delete node_modules inside the plugin package directory before linking it — the app's own @guren/core then satisfies the plugin's peerDependencies with nothing left to shadow it. Published plugins never ship node_modules, so this is a local-testing-only gotcha.

7. Build and publish

{ "scripts": { "build": "tsdown src/index.ts --dts" } }

bun run build && npm publish

Naming Convention

Official (framework-team) plugins: @guren/plugin-{name}. Community plugins: guren-plugin-{name}. Class-based provider names follow {Name}ServiceProvider; definePlugin() factory exports follow {name}Plugin.