From 9e1c4518a869a8af138cf4548e8f4b07082b879f Mon Sep 17 00:00:00 2001
From: Pat Cavit <github@patcavit.com>
Date: Tue, 1 Sep 2026 13:19:09 -0700
Subject: [PATCH 1/3] fix: vite@8 build compatibility

Rolldown doesn't support `moduleSideEffects : "no-treeshake"`, so just always return `true` to ensure nothing gets removed.
---
 packages/vite/vite.js | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/packages/vite/vite.js b/packages/vite/vite.js
index be66268e4..c8a0bda0e 100644
--- a/packages/vite/vite.js
+++ b/packages/vite/vite.js
@@ -253,9 +253,8 @@ module.exports = (
                 code : result,
                 map  : emptyMappings,
 
-                // Disable tree-shaking for CSS modules w/o any classes/values to export
-                // to make sure they're included in the bundle
-                moduleSideEffects : Boolean(namedExports.length) || "no-treeshake",
+                // Disable tree-shaking for CSS modules to make sure they're included in the bundle
+                moduleSideEffects : true,
             };
         },
     };

From d625d1bf301298d354556f1b9ed0c036f5d5c54d Mon Sep 17 00:00:00 2001
From: Pat Cavit <github@patcavit.com>
Date: Tue, 1 Sep 2026 13:20:36 -0700
Subject: [PATCH 2/3] chore: fix lint issue

---
 packages/vite/vite.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/packages/vite/vite.js b/packages/vite/vite.js
index c8a0bda0e..a24f8e0cd 100644
--- a/packages/vite/vite.js
+++ b/packages/vite/vite.js
@@ -220,7 +220,7 @@ module.exports = (
                 return this.error(e);
             }
 
-            const { code : css, namedExports, warnings } = transform(file, processor, pluginOptions);
+            const { code : css, warnings } = transform(file, processor, pluginOptions);
 
             warnings.forEach((warning) => {
                 this.warn(warning);

From 8d9a761689c01932fb989467b47ac6d0888f3a1c Mon Sep 17 00:00:00 2001
From: Pat Cavit <github@patcavit.com>
Date: Tue, 1 Sep 2026 13:23:17 -0700
Subject: [PATCH 3/3] docs: add changeset

---
 .changeset/funny-banks-bet.md | 7 +++++++
 1 file changed, 7 insertions(+)
 create mode 100644 .changeset/funny-banks-bet.md

diff --git a/.changeset/funny-banks-bet.md b/.changeset/funny-banks-bet.md
new file mode 100644
index 000000000..c0434bf46
--- /dev/null
+++ b/.changeset/funny-banks-bet.md
@@ -0,0 +1,7 @@
+---
+"@modular-css/vite": patch
+---
+
+fix: vite@8 build compatibility
+
+Vite plugins can return `moduleSideEffects` from their `transform` hook, but with the switch to Rolldown for built output the valid arguments changed.