# How it works

URL: /docs/plugins/payload-dev-tools/how-it-works

Marker-based plugin discovery, layered gating, server-side draft mode, and why the toolbar persists across navigation.

You don't need any of this to use the plugin — it's here for when you're curious or debugging.

## How it works

- **Plugin discovery is marker-based.** Each `@pro-laico/*` plugin stashes its resolved slugs and
  options on `config.custom` (`payloadSeed`, `payloadImages`, `payloadIcons`, `payloadFonts`,
  `payloadMux`, `payloadRevalidate`). The snapshot builder reads those markers off `payload.config`. No plugin imports,
  so nothing else is a dependency; third-party setups just show fewer panels.
- **The dev page file passes Payload in.** `createDevPage({ payload })` takes an app-supplied
  Payload handle (e.g. `getPayload({ config })`) — the plugin registers no `onInit` and stashes no
  config on `globalThis`.
- **Seeding goes through the seed plugin's own endpoint.** The seed card and toolbar POST to
  `/api/seed`: same gate (`ENABLE_SEED=true` + a logged-in user), same `{ error, issues }`
  responses, surfaced inline.
- **Draft mode flips server-side.** The panel header's draft switch calls `GET /api/dev/draft?enable=1|0`,
  which drives Next's `draftMode()` — the real `__prerender_bypass` cookie, exactly as a preview route
  would set it — then refreshes the page you're on so drafts render in or out. It's URL-addressable
  too (`?to=/path` redirects after flipping), like `/api/dev/stage`.
- **The toolbar persists because it lives in the layout.** Its rows are client-side `<Link>`s, so
  navigating between dev pages never remounts it. It injects one `<style>` tag (all
  `.pdt-`/`.pdtp-` prefixed, no host theme dependency; `--pdt-accent` is the override seam), and it
  only ever receives test *labels*, never render functions.
- **Gating is layered.** Endpoints check per request, pages and toolbar per render. A production
  build ships neither markup nor data.
- **It sits beside Next's own dev indicator, on purpose.** The launcher borrows its idiom and
  defaults to the opposite corner (Next's is bottom-left).

## Next

- [The /dev pages](/docs/plugins/payload-dev-tools/dev-pages) — the routes and the snapshot these mechanics power.
- [The test harness](/docs/plugins/payload-dev-tools/test-harness) — the `defineTest` model.
- [Troubleshooting](/docs/plugins/payload-dev-tools/troubleshooting) — when the gating or draft-mode wiring surprises you.