diff --git a/.github/workflows/performance.yml b/.github/workflows/performance.yml
index 5c597c77..863d5b3d 100644
--- a/.github/workflows/performance.yml
+++ b/.github/workflows/performance.yml
@@ -149,7 +149,14 @@ jobs:
           npm --prefix candidate run build
           (cd candidate && node scripts/bundle-sync.mjs)
           npm --prefix baseline run build
-          (cd baseline && node scripts/bundle-sync.mjs)
+          if [ -f baseline/scripts/bundle-sync.mjs ]; then
+            (cd baseline && node scripts/bundle-sync.mjs)
+          else
+            echo "::notice::The comparison base predates bundle-sync.mjs; materializing its freshly built bundle with the legacy copy path."
+            mkdir -p baseline/custom_components/houseplan/frontend baseline/demo/srv/assets
+            cp baseline/dist/houseplan-card.js baseline/custom_components/houseplan/frontend/houseplan-card.js
+            cp baseline/dist/houseplan-card.js baseline/demo/srv/assets/houseplan-card.js
+          fi
 
       - name: Capture base and candidate profiles
         working-directory: candidate
diff --git a/docs/DEVELOPMENT.md b/docs/DEVELOPMENT.md
index 8a8c5df7..6094fc1f 100644
--- a/docs/DEVELOPMENT.md
+++ b/docs/DEVELOPMENT.md
@@ -152,6 +152,10 @@ on one pinned Chromium/CI profile, applies relative and absolute budgets, and
 uploads both reports plus the comparison. A developer-laptop report remains a
 diagnostic and must not be used to loosen CI limits. See
 `demo/performance/README.md`.
+When the comparison base predates `scripts/bundle-sync.mjs`, the workflow still
+builds that exact tree and materializes its fresh bundle through the equivalent
+legacy copy path. This keeps old stable releases usable as performance baselines
+without borrowing build output from the candidate.
 Both browser diagnostics require a freshly built/copied demo bundle. Rollup
 embeds a SHA-256 fingerprint of `src/` plus the locked package and
 Rollup/TypeScript build inputs; benchmark/golden runners fail before