diff --git a/.github/workflows/notify-unitsdb-js.yml b/.github/workflows/notify-unitsdb-js.yml
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+++ b/.github/workflows/notify-unitsdb-js.yml
@@ -0,0 +1,52 @@
+# Not auto-generated by Cimas — hand-maintained cross-repo trigger.
+name: notify-unitsdb-js
+
+# After every unitsdb release (which bumps lib/unitsdb/version.rb on
+# main), dispatch to unitsml/unitsdb-js so it can compile the new
+# version and publish to npm as @unitsml/unitsdb.
+#
+# unitsdb-js's release.yml is idempotent: if a version is already on
+# npm it skips cleanly, so re-running after a transient failure (or
+# re-dispatching) is safe.
+
+on:
+  push:
+    branches: [main]
+    paths:
+      - "lib/unitsdb/version.rb"
+
+permissions:
+  contents: read
+
+jobs:
+  dispatch:
+    if: contains(github.event.head_commit.message, 'Bump unitsdb to')
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v6
+        with:
+          fetch-depth: 2
+
+      - name: Extract released version
+        id: ver
+        run: |
+          set -eu
+          VERSION=$(grep -oE 'VERSION = "[^"]+"' lib/unitsdb/version.rb | head -1 | cut -d'"' -f2)
+          if [ -z "$VERSION" ]; then
+            echo "::error::could not read VERSION from lib/unitsdb/version.rb"
+            exit 1
+          fi
+          echo "version=$VERSION" >> "$GITHUB_OUTPUT"
+          echo "Detected version $VERSION"
+
+      - name: Dispatch do-release to unitsml/unitsdb-js
+        uses: peter-evans/repository-dispatch@v3
+        with:
+          token: ${{ secrets.UNITSML_CI_PAT_TOKEN }}
+          repository: unitsml/unitsdb-js
+          event-type: do-release
+          client-payload: |
+            {
+              "version": "${{ steps.ver.outputs.version }}",
+              "ruby_ref": "v${{ steps.ver.outputs.version }}"
+            }