Enable dynamic HTML in minimal mode

packages/next/server/base-server.ts

@@ -289,7 +289,7 @@ export default abstract class Server {
     } = this.nextConfig
 
     this.buildId = this.getBuildId()
-    this.minimalMode = minimalMode
+    this.minimalMode = minimalMode || !!process.env.NEXT_PRIVATE_MINIMAL_MODE
 
     const serverComponents = this.nextConfig.experimental.serverComponents
     this.serverComponentManifest = serverComponents
@@ -1162,7 +1162,6 @@ export default abstract class Server {
         !isSSG &&
         !isLikeServerless &&
         !query.amp &&
-        !this.minimalMode &&
         typeof components.Document?.getInitialProps !== 'function'
     }
 

test/production/react-18-streaming-ssr/index.test.ts

@@ -0,0 +1,44 @@
+import { createNext } from 'e2e-utils'
+import { NextInstance } from 'test/lib/next-modes/base'
+import { renderViaHTTP } from 'next-test-utils'
+
+describe('react-18-streaming-ssr in minimal mode', () => {
+  let next: NextInstance
+
+  beforeAll(async () => {
+    process.env.NEXT_PRIVATE_MINIMAL_MODE = '1'
+
+    next = await createNext({
+      files: {
+        'pages/index.server.js': `
+          export default function Page() { 
+            return <p>static streaming</p>
+          }
+        `,
+      },
+      nextConfig: {
+        experimental: {
+          reactRoot: true,
+          serverComponents: true,
+          runtime: 'nodejs',
+        },
+      },
+      dependencies: {
+        react: '18.0.0-rc.0',
+        'react-dom': '18.0.0-rc.0',
+      },
+      skipStart: true,
+    })
+
+    await next.start()
+  })
+  afterAll(() => {
+    delete process.env.NEXT_PRIVATE_MINIMAL_MODE
+    next.destroy()
+  })
+
+  it('should generate html response by streaming correctly', async () => {
+    const html = await renderViaHTTP(next.url, '/')
+    expect(html).toContain('static streaming')
+  })
+})