diff --git a/services/clsi/app/js/OutputFileFinder.js b/services/clsi/app/js/OutputFileFinder.js
index 5b581a9a7d..49cf4e2f05 100644
--- a/services/clsi/app/js/OutputFileFinder.js
+++ b/services/clsi/app/js/OutputFileFinder.js
@@ -20,16 +20,29 @@ async function walkFolder(compileDir, d, files, allEntries) {
   }
 }
 
+// Media that an HTML/RevealJS deck references at runtime (img/video/audio).
+// These are usually project *input* files, which would normally be excluded
+// from the output set — but for HTML output the browser fetches them from the
+// output path, so they must be served. (For PDF output they are embedded, so
+// the exclusion still applies.)
+const MEDIA_REGEX =
+  /\.(png|jpe?g|gif|svg|webp|avif|bmp|ico|mp4|webm|ogg|ogv|mov|m4v|mp3|wav|m4a|woff2?|ttf|otf)$/i
+
 async function findOutputFiles(resources, directory) {
   const files = []
   const allEntries = []
   await walkFolder(directory, '', files, allEntries)
 
   const incomingResources = new Set(resources.map(resource => resource.path))
+  // For HTML output (Quarto/RevealJS), referenced media must be served even
+  // though it is an input file; see MEDIA_REGEX above.
+  const hasHtmlOutput = files.includes('output.html')
 
   const outputFiles = []
   for (const path of files) {
-    if (incomingResources.has(path)) continue
+    if (incomingResources.has(path)) {
+      if (!(hasHtmlOutput && MEDIA_REGEX.test(path))) continue
+    }
     if (path === '.project-sync-state') continue
     outputFiles.push({
       path,