diff --git a/features/messaging/frontend-public/vite.config.ts b/features/messaging/frontend-public/vite.config.ts
index 50779d57c..51c435dd8 100644
--- a/features/messaging/frontend-public/vite.config.ts
+++ b/features/messaging/frontend-public/vite.config.ts
@@ -61,15 +61,14 @@ export default defineConfig({
         inline: ['@lilith/text-processing-content-flagging'],
       },
     },
-    poolOptions: {
-      forks: {
-        // Limit to 1 concurrent fork. The deps.inline Vite processing of the
-        // content-flagging package consumes significant heap per fork. Running
-        // multiple forks simultaneously exhausts system memory.
-        maxForks: 1,
-        minForks: 1,
-      },
-    },
+    // Vitest 4 top-level pool options (replaces deprecated test.poolOptions).
+    // Limit to 1 concurrent worker — deps.inline Vite processing of the
+    // content-flagging package consumes significant heap per worker.
+    maxWorkers: 1,
+    // Increase heap for forks that inline the content-flagging package.
+    // The barrel re-exports UI components pulling in styled-components +
+    // React transitive deps, which bloats the Vite transform cache.
+    execArgv: ['--max-old-space-size=4096'],
   },
   build: {
     outDir: 'dist',