From e3ec3a8ba31d08df4ae3ec8bf178a30d567ee527 Mon Sep 17 00:00:00 2001
From: Anthony GAEREMYNCK <1@anthony.sh>
Date: Sun, 2 Aug 2026 12:51:09 +0200
Subject: [PATCH] fix(seo): load the entry module with defer instead of async
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window.__VITE_REACT_SSG_HASH__ (read by every route's data loader to fetch
static-loader-data-manifest-<hash>.json) is set by a plain inline <script>
placed later in the document body. With script: 'async', the module script
in <head> can start executing as soon as it finishes downloading, racing
ahead of the HTML parser reaching that later inline script — intermittently
reading the hash as undefined depending on network/cache timing, and
producing a 404 on .../static-loader-data-manifest-undefined.json followed
by a React hydration crash (error #418).

'defer' guarantees the module only executes after the full document,
including that inline script, has been parsed — this removes the race
structurally rather than just making it less likely.
---
 frontend/vite.config.js | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/frontend/vite.config.js b/frontend/vite.config.js
index 41c0723..0ab79c1 100644
--- a/frontend/vite.config.js
+++ b/frontend/vite.config.js
@@ -25,7 +25,14 @@ export default defineConfig({
   },
   ssgOptions: {
     dirStyle: 'nested',
-    script: 'async',
+    // 'defer' (not 'async'): the entry module reads window.__VITE_REACT_SSG_HASH__,
+    // which is set by a plain inline <script> placed later in the document body.
+    // An async module can start executing as soon as it's fetched, racing ahead
+    // of the parser reaching that later inline script — intermittently reading
+    // it as undefined depending on network/cache timing. defer guarantees the
+    // module only runs after the full document (including that inline script)
+    // has been parsed.
+    script: 'defer',
     onFinished: writeSitemap,
   },
 });
