[Performance]: Build-time content sync starts miniflare via the temp Vite dev server

Astro Info

Astro                    v6.1.6
Vite                     v7.3.2
Node                     v25.9.0
System                   macOS (x64)
Package Manager          npm
Output                   static
Adapter                  @astrojs/cloudflare (v13.1.9)
Integrations             none

Describe the Bug

During astro build, the syncInternal function in core/sync/index.js creates a temporary Vite dev server (createTempViteServer) to resolve content collection configs and generate type declarations. Because this is a real dev server (created via Vite's createServer), every plugin's configureServer hook runs — including adapter plugins that start heavy runtimes.

With @astrojs/cloudflare, the @cloudflare/vite-plugin hooks into configureServer to start miniflare (the workerd runtime). This adds ~1–3.5 s of overhead on every build, even though the temp server only needs to resolve virtual modules for type generation. It never handles HTTP requests.

The overhead is especially noticeable in CI and in server-mode builds where the actual Vite build phases (prerender + SSR + client) can be as low as ~1.5 s for a small project — making the sync overhead ~40% of the total build time.

Measured in this MRE (minimal project)

Phase	Time
Types Generated (sync)	1.24 s
Prerender build	0.88 s
SSR build	0.66 s
Client build	0.007 s
Total build	3.30 s

Measured in a real project (~116 .astro components, SCSS, Storyblok)

Phase	Before fix	After fix
Types Generated	3.6 s	125 ms
Total build	~13 s	~9.2 s

Root Cause

Two issues combine:

1. Astro's sync creates a full dev server (createServer) when a lighter-weight approach would suffice for resolving virtual modules and generating types. The temp server config already passes { middlewareMode: true, hmr: false, watch: null, ws: false } — but configureServer hooks still fire.

2. optimizeDeps: { noDiscovery: true } only applies at the top level (client environment). In Vite 7's Environment API, the Cloudflare adapter's configEnvironment hook checks _options.optimizeDeps?.noDiscovery per-environment. Since server environments (ssr, astro, prerender) don't inherit the top-level flag, the adapter injects its large optimizeDeps.include list (~30 entries), forcing the optimizer to pre-bundle them even in the temp server.

What's the expected result?

Type generation during astro build should not start miniflare or perform dependency pre-bundling in adapter-managed environments. For a minimal project, this phase should complete in < 250 ms, not > 1 s.

Potential fix

The createTempViteServer function in core/sync/index.js should:

1. Set optimizeDeps.noDiscovery on every environment, not just the top level, so adapter configEnvironment hooks see the flag and skip their include lists:

const noOptimize = { optimizeDeps: { noDiscovery: true, include: [] } };
// passed to createVite:
environments: {
  client: noOptimize,
  ssr: noOptimize,
  astro: noOptimize,
  prerender: noOptimize,
},

2. Strip configureServer hooks from adapter plugins that start runtimes, since the temp server never serves requests:

plugins: [{
  name: "sync:strip-adapter-hooks",
  enforce: "pre",
  configResolved(config) {
    for (const plugin of config.plugins) {
      if (plugin.configureServer && /cloudflare/.test(plugin.name)) {
        delete plugin.configureServer;
      }
    }
  }
}]

A more general solution might be to use Vite's ModuleRunner directly instead of creating a full dev server, but the plugin-stripping approach is a targeted fix that preserves the existing architecture.

Link to Minimal Reproducible Example

https://github.com/adamchal/astro-sync-perf

Participation

• I am willing to submit a pull request for this issue.