diff --git a/.github/workflows/bundle-stats.yml b/.github/workflows/bundle-stats.yml
new file mode 100644
index 00000000..a9dcb0e5
--- /dev/null
+++ b/.github/workflows/bundle-stats.yml
@@ -0,0 +1,57 @@
+name: Bundle Stats
+on:
+  workflow_call:
+    inputs:
+      mode:
+        required: true
+        type: string
+        description: "'store' or 'compare'"
+      branch:
+        required: true
+        type: string
+    outputs:
+      stats:
+        description: "Bundle stats comparison"
+        value: ${{ jobs.bundle-stats.outputs.stats }}
+
+jobs:
+  bundle-stats:
+    runs-on: ubuntu-latest
+    outputs:
+      stats: ${{ steps.gist-ops.outputs.stats }}
+    steps:
+      - uses: actions/github-script@v6
+        id: gist-ops
+        with:
+          script: |
+            const gistId = '${{ secrets.BUNDLE_STATS_GIST_ID }}';
+
+            async function getGistContent() {
+              const { data } = await github.rest.gists.get({ gist_id: gistId });
+              return JSON.parse(data.files['bundle-stats.json'].content || '{}');
+            }
+
+            async function updateGistContent(content) {
+              await github.rest.gists.update({
+                gist_id: gistId,
+                files: {
+                  'bundle-stats.json': {
+                    content: JSON.stringify(content, null, 2)
+                  }
+                }
+              });
+            }
+
+            if ('${{ inputs.mode }}' === 'store') {
+              const stats = require('/tmp/bundle-stats.json');
+              const content = await getGistContent();
+              content['${{ inputs.branch }}'] = stats;
+              await updateGistContent(content);
+            } else {
+              const content = await getGistContent();
+              const baseStats = content['${{ inputs.branch }}'];
+              const newStats = require('/tmp/bundle-stats.json');
+
+              const comparison = `minecraft.html (normal build gzip)\n${baseStats.total}MB (${baseStats.gzipped}MB compressed) -> ${newStats.total}MB (${newStats.gzipped}MB compressed)`;
+              core.setOutput('stats', comparison);
+            }
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 92b7e7f3..46a2de6b 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -21,6 +21,13 @@ jobs:
         uses: pnpm/action-setup@v4
       - run: pnpm install
       - run: pnpm check-build
+      - name: Create zip package for size comparison
+        run: |
+          mkdir -p package
+          cp -r dist package/
+          cd package
+          zip -r ../self-host.zip .
+      - run: pnpm build-single-file
       - run: pnpm build-playground
       - run: pnpm build-storybook
       - run: pnpm test-unit
@@ -40,6 +47,58 @@ jobs:
       #   if: ${{ github.event.pull_request.base.ref == 'release' }}
       #   env:
       #     GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Parse Bundle Stats
+        run: |
+          SIZE_BYTES=$(du -s dist/single/minecraft.html 2>/dev/null | cut -f1)
+          GZIP_BYTES=$(du -s self-host.zip 2>/dev/null | cut -f1)
+          SIZE=$(echo "scale=2; $SIZE_BYTES/1024/1024" | bc)
+          GZIP_SIZE=$(echo "scale=2; $GZIP_BYTES/1024/1024" | bc)
+          echo "{\"total\": ${SIZE}, \"gzipped\": ${GZIP_SIZE}}" > /tmp/bundle-stats.json
+
+      - name: Compare Bundle Stats
+        id: compare
+        uses: ./.github/workflows/bundle-stats
+        with:
+          mode: compare
+          branch: ${{ github.event.pull_request.base.ref }}
+
+      - name: Store Bundle Stats
+        if: github.event.pull_request.base.ref == 'next'
+        uses: ./.github/workflows/bundle-stats
+        with:
+          mode: store
+          branch: ${{ github.event.pull_request.base.ref }}
+
+      - name: Update PR Description
+        uses: actions/github-script@v6
+        with:
+          script: |
+            const { data: pr } = await github.rest.pulls.get({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              pull_number: context.issue.number
+            });
+
+            let body = pr.body || '';
+            const statsMarker = '### Bundle Size';
+            const comparison = '${{ steps.compare.outputs.stats }}';
+
+            if (body.includes(statsMarker)) {
+              body = body.replace(
+                new RegExp(`${statsMarker}[^\n]*\n[^\n]*`),
+                `${statsMarker}\n${comparison}`
+              );
+            } else {
+              body += `\n\n${statsMarker}\n${comparison}`;
+            }
+
+            await github.rest.pulls.update({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              pull_number: context.issue.number,
+              body
+            });
   # dedupe-check:
   #   runs-on: ubuntu-latest
   #   if: github.event.pull_request.head.ref == 'next'
diff --git a/rsbuild.config.ts b/rsbuild.config.ts
index 1701fc5c..36ccb9b0 100644
--- a/rsbuild.config.ts
+++ b/rsbuild.config.ts
@@ -203,6 +203,12 @@ const appConfig = defineConfig({
                     })
                     build.onAfterBuild(async () => {
                         if (SINGLE_FILE_BUILD) {
+                            // check that only index.html is in the dist/single folder
+                            const singleBuildFiles = fs.readdirSync('./dist/single')
+                            if (singleBuildFiles.length !== 1 || singleBuildFiles[0] !== 'index.html') {
+                                throw new Error('Single file build must only have index.html in the dist/single folder. Ensure workers are imported & built correctly.')
+                            }
+
                             // process index.html
                             const singleBuildHtml = './dist/single/index.html'
                             let html = fs.readFileSync(singleBuildHtml, 'utf8')