> ## Documentation Index
> Fetch the complete documentation index at: https://docs.stage.systems/llms.txt
> Use this file to discover all available pages before exploring further.

# Building on Stage

> What a Stage site is made of, the contract a site must meet to be editable and measurable, and how these pages are organised.

These pages are for the person building or extending a Stage site. They describe the **contract**: what a site renders so the admin can edit it, what it declares so the admin can add to it, and what it emits so Stage can measure it. How the editor behaves for a user is in the [Guides](/getting-started/how-stage-works); these pages link there rather than repeat it.

## What a Stage site is

```
                          Stage database
                (PostgreSQL + auth + realtime)
                              |
          +-------------------+-------------------+
          |                                       |
     Your site                              Stage API
  (static build, one                    (one shared service)
   deployment per site)                 uploads, publishing,
          |                             posting, links, forms,
   +------+------+                      analytics reads
   |             |                                |
 public       /admin  ───────────────────────────▶│
 pages     (same-origin frame
 (no editor  + the admin shell)
  JS)
```

| Part             | What it is                                                                                                                                                                                                                                                                            | Who runs it                                      |
| ---------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------ |
| **The site**     | An Astro static build. Pages, articles, globals and media are read from the database at build time and rendered to HTML with inert edit anchors. No editor code ships to visitors. The SDK's small inline scripts for consent and engagement do, and form submission needs JavaScript | Deployed once per site, on the site's own domain |
| **The admin**    | `/admin` on the same domain. A top bar hosting lazily loaded tools. Generic: it edits any component by id and path and contains no design                                                                                                                                             | Loaded only for a signed-in member               |
| **The API**      | One service, deployed once, shared by every site. Holds every secret. Every route is org-scoped                                                                                                                                                                                       | Operated by Stage                                |
| **The database** | Every content, media and analytics row carries an `org_id`. Row-level security enforces the scope                                                                                                                                                                                     | Operated by Stage                                |

## The two packages

| Package           | Contains                                                                                                                                                                            |
| ----------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `@sp-stage/sdk`   | Pure data and logic. Queries, the id and path write model, versioned saves and merge, the anchor helpers, the edge middleware, image URL helpers, sanitisers, the analytics scripts |
| `@sp-stage/admin` | The `/admin` shell and its tools (React)                                                                                                                                            |
| `@sp-stage/next`  | Next.js sites only: the anchors as React props, the admin mount, the zero-JS edit canvas, the publish handler. See [Next.js sites](/developers/next/overview)                       |

A site pins an exact version of both. They release together as one Stage version. See [Versioning and releases](/developers/reference/releases).

## The contract in one paragraph

A site **renders** each stored component through its own renderer and spreads the anchor helpers onto the wrapper and every editable field. That alone makes existing content editable. To make lists **addable**, the site passes a schema to the admin naming which fields are lists and what a new item looks like. To be **measured**, the site re-exports the SDK middleware and includes the SDK's inline scripts in its layout. Nothing in the platform knows a site's design.

## Read in order

<Steps>
  <Step title="Set up a site">
    The template, the env, the admin mount, local development. [Read it](/developers/setup).
  </Step>

  <Step title="Make content editable">
    [Anchors](/developers/editing/anchors), [components](/developers/editing/components), and [the write model](/developers/editing/write-model) underneath.
  </Step>

  <Step title="Make content addable">
    [Schemas](/developers/structure/schemas), [the edit notch](/developers/structure/edit-notch), then the [blog](/developers/structure/blog) and [forms](/developers/structure/forms) recipes.
  </Step>

  <Step title="Measure">
    [Tracking](/developers/analytics/tracking), [campaign landing](/developers/analytics/campaign-landing), and [custom funnels](/developers/analytics/custom-funnels).
  </Step>
</Steps>

<Note>
  **Stage only.** These pages document the platform contract. How a particular site's design is produced (design tools, generators, internal playbooks) is not Stage and is not here.
</Note>