astro/.changeset/stupid-points-refuse.md

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New build configuration

The ability to customize SSR build configuration more granularly is now available in Astro. You can now customize the output folder for server (the server code for SSR), client (your client-side JavaScript and assets), and serverEntry (the name of the entrypoint server module). Here are the defaults:

import { defineConfig } from 'astro/config';

export default defineConfig({
  output: 'server',
  build: {
    server: './dist/server/',
    client: './dist/client/',
    serverEntry: 'entry.mjs',
  }
});

These new configuration options are only supported in SSR mode and are ignored when building to SSG (a static site).

Integration hook change

The integration hook astro:build:start includes a param buildConfig which includes all of these same options. You can continue to use this param in Astro 1.x, but it is deprecated in favor of the new build.config options. All of the built-in adapters have been updated to the new format. If you have an integration that depends on this param we suggest upgrading to do this instead:

export default function myIntegration() {
  return {
    name: 'my-integration',
    hooks: {
      'astro:config:setup': ({ updateConfig }) => {
        updateConfig({
          build: {
            server: '...'
          }
        });
      }
    }
  }
}