@expo/snapback-vite

@expo/snapback-vite is Snapback's local-development Vite plugin. It attaches to or manages the backend lifecycle, resolves generated imports through the digest-verified codegen cache, exposes sanitized state through virtual:snapback/dev, and relays only allowlisted application-data HTTP and WebSocket routes under /__snapback.

This is a project development dependency, not a production server adapter or a general reverse proxy. The React starter created by @expo/snapback-cli installs and configures it already. Install it directly only when adding the managed Snapback loop to an existing Vite application.

Add the managed development integration

For a new application, the supported route is the prepared starter:

npm install --global @expo/snapback-cli
snapback new my-app --template react
cd my-app
bun install
bun run dev

An existing Vite application can use the same plugin shape:

import { defineConfig } from 'vite';
import { snapbackDev } from '@expo/snapback-vite';

export default defineConfig({
  plugins: [
    snapbackDev({
      server: { mode: 'managed', port: 3210 },
      setup: { backendDirectory: 'snapback' },
      generatedRoots: ['snapback/generated'],
    }),
  ],
});

Run that configuration with the application's ordinary Vite command. The plugin consumes the fixed-port/external-client profile of snapback dev, pins Vite's actual loopback origin with strictPort, declares that exact origin to the backend lifecycle, and waits for the authoritative snapback.application-ready.v1 receipt. Attach mode compares the receipt's complete application, authority, artifact, target-profile, capability, and admission bind-set with live operational readiness before asking the shared CLI lifecycle to perform its idempotent generated load and binding reissue. An expired binding is reissued only after that identity cut. Browser code receives a same-origin projection of the receipt-issued binding at /__snapback; the backend origin, admin token, receipt/runtime paths, and qualified-binary facts remain private.

The relay registry includes the exact server-registered methods under /auth/password/* and /auth/recovery/*, so the generated binding supports signup, sign-in, recovery, logout, and live data on that one page origin. This is not a broad /auth/* proxy; unknown and privileged auth routes remain refused. See the served Guide's authoring loop.

Documentation outside a checkout

A running Snapback server serves the Guide compiled into that exact build. These links use the first default development port; use the origin printed by snapback dev or snapback start if yours differs.

• Follow the authoring loop for the complete React/Vite development flow.
• Read generated artifact custody for verified generated-import behavior.
• Read first: the start packets — the budgeted per-template first read (LLP 0259).
• Look up (do not linear-read) the capability index before assuming a relayed route or target is supported.
• Run snapback guide or snapback guide <query> to browse or search the embedded Guide.
• Run snapback mcp for the same build-bound corpus as read-only MCP resources, starting at snapback-guide://manifest.