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assistant tools](/docs/extending/embedding/assistant-harness/)UI kit[The Jx UI kit](/docs/extending/ui-kit/)Reference[Protocol routes](/docs/extending/reference/studio-routes/)[Implementation status](/docs/extending/reference/implementation-status/)[Spec changelog](/docs/extending/reference/spec-changelog/)[Standards alignment](/docs/extending/reference/standards/)Contributing[Working in the monorepo](/docs/extending/contributing/monorepo/)[Contributing to these docs](/docs/extending/contributing/docs/)[AI assistant evals](/docs/extending/contributing/ai-evals/) # Tutorial: a guestbook extension This tutorial builds `@acme/jx-guestbook`, the spec's second worked example: a moderated, auth-gated guestbook a site enables with one `extensions` line. Where the [TOML tutorial](/docs/extending/extensions/tutorial-toml-format) exercised the format surface, this one demonstrates the full stack: a `project.json` section with a Studio settings form, a dynamic table, a server mount cooperating with auth, and page state that compiles down to core defs. It builds **on** the connector and auth extensions as dependencies rather than reimplementing them. Plan on about an hour, reading the first-party sources alongside. **Prerequisites**: [Project sections](/docs/extending/extensions/project-sections), [Server mounts](/docs/extending/extensions/server), and [Connectors](/docs/extending/extensions/connectors); a test project with `@jxsuite/connector` and `@jxsuite/auth` already enabled ([Databases](/docs/studio/data)). The spec describes this example at the architecture level, and this tutorial keeps that altitude: each step pins down the declarations and points at the first-party file implementing the same pattern, rather than reprinting implementation code. ## 1. Manifest and fragment Scaffold the package the same way as the [TOML tutorial](/docs/extending/extensions/tutorial-toml-format): a `package.json` with a `"jx"` field, a `jx-extension.json` naming one section class (say `Guestbook`), and (because this extension owns a `project.json` section) a project [schema fragment](/docs/extending/extensions/schema-composition) listed under `schemas.project`. The fragment's schema defines the section value, `{ table, moderation }`: which table entries land in, and whether they await approval. The section class declares ownership plus a generic settings form: ```json shiki ``` You should now see, after enabling the extension in your test project and running `jx schema`, a `guestbook` key validating in `project.json`, and a **Guestbook** section rendered from your fragment in Studio's Settings, with no Studio code written. The connector's `extensions/connector/schemas/project.fragment.schema.json` and `Data.class.json` are the fuller reference for this step. ## 2. The table The guestbook stores entries in an ordinary connector table instead of hand-rolled SQL. Declare a `projectData`[capability](/docs/extending/extensions/capabilities) on the section class that materializes a `data`-style table definition from the section value (columns `name` and `message`, readable by anyone, writable by signed-in users): ```json shiki ``` Because this is a standard table definition, entries flow through the connector's standard mount and DDL sync: `jx db push` creates the table additively, the dev server's local SQLite stand-in serves it immediately, and the Studio [data grid](/docs/studio/data/grid) doubles as your moderation console. No custom SQL anywhere. ## 3. The mount Moderation needs server-side logic, so the class also declares a [server block](/docs/extending/extensions/server): ```json shiki ``` Order 30 places it after auth (10) and the data mount (20), so by the time your `mount(options, ctx)` runs, `ctx.auth` is published and `/_jx/data` is live. The mount returns a fetch-style handler that reads `ctx.auth` for session lookups and proxies moderated writes into `/_jx/data/guestbook`, accepting a public submission, stamping it unapproved when `moderation` is on, and letting the table's own permission rules govern everything else. `Auth.mount` in `extensions/auth/src/worker.ts` is the pattern to copy: per-isolate state in the closure, the handler as the return value, secrets only ever read from `env`. You should now see `jx dev` answering under `/_jx/guestbook`, with the same behavior the generated worker will have in production. ## 4. The page The visitor-facing page needs no extension-specific runtime. It uses the connector's state classes: a `TableQuery` entry listing approved entries, and a form whose submit posts through a `TableInsert` action. Both are [lowered](/docs/extending/extensions/capabilities) at compile time, so queries become plain `Request` fetches and the action becomes an inline `Function` handler. No extension code ships to the browser, and the `_v` read-after-write convention re-runs the listing query as soon as a write lands. ## 5. Ship it A project adds the package and syncs: ```json shiki ``` Then `jx schema && jx db push`. You should now have a moderated, auth-gated guestbook with `project.json` validation, a Studio settings section, and dev-server parity. None of it required changes to any core package. ## What you built | Piece | Mechanism | First-party reference | | ------------------- | ------------------------------------------ | ------------------------------------------------ | | `guestbook` section | `project` block + schema fragment | `extensions/connector/src/Data.class.json` | | Settings form | `$studio.settings` (`layout: "form"`) | `extensions/auth/src/Auth.class.json` | | Entries table | `projectData` → connector table definition | `extensions/connector/src/Data.class.json` | | `/_jx/guestbook` | `server` block + `mount`, order 30 | `extensions/auth/src/worker.ts` | | Page state | `TableQuery` / `TableInsert`, lowered | `extensions/connector/src/TableQuery.class.json` | ## Next steps - [Security and secrets](/docs/extending/extensions/security): the fail-closed rules your mount inherits. - [Server mounts](/docs/extending/extensions/server): the shared-context contract in full. - [First-party extensions](/docs/extending/extensions/first-party): the three packages this tutorial leaned on. ✕ Start here[Overview](/docs/start/)Get started[Install Jx Studio](/docs/start/install/)[Your first project](/docs/start/first-project/)[A tour of Jx Studio](/docs/start/studio-tour/)Tutorials[Tutorial: interactive component](/docs/start/first-component/)[Tutorial: blog with collections](/docs/start/first-collection/)[Video tutorials](/docs/start/videos/)Coming from another tool[Coming from WordPress](/docs/start/coming-from-wordpress/)[Coming from Webflow or Framer](/docs/start/coming-from-webflow/)[Coming from Wix or Squarespace](/docs/start/coming-from-wix/)[Coming from Lovable or Builder.io](/docs/start/coming-from-ai-builders/)Studio[Overview](/docs/studio/)[The desktop app](/docs/studio/desktop/)The workspace[Overview](/docs/studio/interface/)[Welcome screen](/docs/studio/interface/welcome-screen/)[Editors and views](/docs/studio/interface/modes/)[The 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