Move away from build based style hash

packages/site_shared/lib/_sass/components/_code.scss

@@ -188,7 +188,7 @@ pre {
         list-style: none;
         position: relative;
 
-        // Caret at the beginning of the folding range. 
+        // Caret at the beginning of the folding range.
         span.material-symbols {
           position: absolute;
           cursor: pointer;

packages/site_shared/lib/server_util.dart

@@ -0,0 +1,8 @@
+// Copyright 2026, the Flutter authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that
+// can be found in the LICENSE file.
+
+/// Utilities meant to be used when running on the server.
+library;
+
+export 'src/utils/cache_busted_build_asset_url.dart';

packages/site_shared/lib/src/layouts/dash_layout.dart

@@ -11,6 +11,7 @@ import 'package:jaspr_content/jaspr_content.dart';
 import '../../components/common/client/cookie_notice.dart';
 import '../../components/layout/banner.dart';
 import '../../util.dart';
+import '../utils/cache_busted_build_asset_url.dart';
 
 /// The base Jaspr Content layout for all sites.
 abstract class DashLayout implements PageLayout {
@@ -52,7 +53,8 @@ abstract class DashLayout implements PageLayout {
     'https://fonts.googleapis.com/css2?family=Material+Symbols+Outlined:opsz,wght,FILL,GRAD@24,400,0..1,0',
   ];
 
-  String get stylesHash;
+  /// The stylesheet URL for the site's built styles.
+  String get stylesUrl => '/assets/css/main.css';
 
   Iterable<Component> buildExtraHead(Page page) => const [];
 
@@ -149,7 +151,7 @@ abstract class DashLayout implements PageLayout {
       // Set site styles.
       link(
         rel: 'stylesheet',
-        href: '/assets/css/main.css?hash=$stylesHash',
+        href: cacheBustedBuildAssetUrl(stylesUrl),
       ),
 
       // Set site scripts.

packages/site_shared/lib/src/utils/cache_busted_build_asset_url.dart

@@ -0,0 +1,60 @@
+// Copyright 2026, the Flutter authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that
+// can be found in the LICENSE file.
+
+import 'dart:convert';
+import 'dart:io';
+
+import 'package:crypto/crypto.dart';
+import 'package:jaspr/server.dart';
+import 'package:path/path.dart' as path;
+
+final Map<String, String> _cacheBustedBuildAssetUrls = {};
+
+/// The [assetUrl] with a content hash appended.
+///
+/// Jaspr writes web assets to `build/jaspr` before it
+/// starts the static site renderer.
+/// This function reads the built asset and appends a
+/// truncated SHA-256 hash as a query parameter.
+/// Outside static generation, it returns [assetUrl] unchanged.
+///
+/// If the built asset doesn't exist, throws a [FileSystemException].
+/// If the built asset is empty, throws a [StateError].
+String cacheBustedBuildAssetUrl(String assetUrl) {
+  if (!kGenerateMode) {
+    return assetUrl;
+  }
+
+  return _cacheBustedBuildAssetUrls.putIfAbsent(assetUrl, () {
+    final assetUri = Uri.parse(assetUrl);
+    final assetPath = path.joinAll([
+      'build',
+      'jaspr',
+      ...assetUri.pathSegments,
+    ]);
+    final assetFile = File(assetPath);
+    if (!assetFile.existsSync()) {
+      throw FileSystemException(
+        'Built asset not found. Ensure web assets are built before rendering.',
+        assetFile.path,
+      );
+    }
+
+    final bytes = assetFile.readAsBytesSync();
+    if (bytes.isEmpty) {
+      throw StateError('Built asset is empty: ${assetFile.path}');
+    }
+
+    final digest = sha256.convert(bytes);
+    final hash = base64Url.encode(digest.bytes).substring(0, 12);
+    return assetUri
+        .replace(
+          queryParameters: {
+            ...assetUri.queryParameters,
+            'hash': hash,
+          },
+        )
+        .toString();
+  });
+}

packages/site_shared/pubspec.yaml

@@ -6,7 +6,6 @@ environment:
   sdk: ^3.13.0-0
 
 dependencies:
-  build: ^4.0.7
   collection: ^1.19.1
   crypto: ^3.0.7
   html: ^0.15.6

sites/docs/lib/src/layouts/flutter_layout.dart

@@ -15,7 +15,6 @@ import '../components/layout/header.dart';
 import '../components/layout/sidenav.dart';
 import '../models/sidenav_model.dart';
 import '../pages/markdown.dart';
-import '../style_hash.dart';
 
 /// The base Jaspr Content layout for wrapping site content.
 abstract class FlutterDocsLayout extends DashLayout {
@@ -42,9 +41,6 @@ abstract class FlutterDocsLayout extends DashLayout {
   @override
   String get analyticsId => 'UA-67589403-1';
 
-  @override
-  String get stylesHash => generatedStylesHash;
-
   String get defaultSidenav => 'default';
 
   bool get allowBreadcrumbs => true;

sites/docs/pubspec.yaml

@@ -7,7 +7,6 @@ environment:
   sdk: ^3.13.0-0
 
 dependencies:
-  build: ^4.0.7
   collection: ^1.19.1
   html: ^0.15.6
   http: ^1.6.0

sites/www/lib/src/layouts/default_layout.dart

@@ -5,12 +5,12 @@
 import 'package:jaspr/dom.dart';
 import 'package:jaspr/server.dart';
 import 'package:jaspr_content/jaspr_content.dart';
+import 'package:site_shared/server_util.dart';
 
 import '../components/layout/footer.dart';
 import '../components/layout/header.dart';
 import '../components/pages/consultants_cookie_snack.dart';
 import '../models/content/banner_content.dart';
-import '../style_hash.dart';
 import '../utils/asset_utils.dart';
 import '../utils/data_utils.dart';
 
@@ -176,9 +176,9 @@ class DefaultLayout extends PageLayout {
               rel: 'stylesheet',
             ),
 
-            // Project Styles
-            const link(
-              href: '/main.css?hash=$generatedStylesHash',
+            // Set site styles.
+            link(
+              href: cacheBustedBuildAssetUrl('/main.css'),
               rel: 'stylesheet',
             ),
           ],