diff --git a/Jenkinsfile b/Jenkinsfile
index 6cbfa12..8b31e09 100644
--- a/Jenkinsfile
+++ b/Jenkinsfile
@@ -98,10 +98,15 @@ spec:
           script {
             sh '''
               set -euo pipefail
-              SEMVER="$(git describe --tags --abbrev=0 --match 'v*' 2>/dev/null || jq -r '.version' frontend/package.json || echo '0.1.0')"
-              # Accept bare semver or leading v.
-              if ! echo "$SEMVER" | grep -Eq '^v?[0-9]+\\.[0-9]+\\.[0-9]+(\\-[0-9A-Za-z.-]+)?$'; then
-                SEMVER="0.1.0"
+              if git describe --tags --exact-match >/dev/null 2>&1; then
+                SEMVER="$(git describe --tags --exact-match)"
+              else
+                BASE="$(jq -r '.version' frontend/package.json || echo '0.1.0')"
+                SEMVER="${BASE}-${BUILD_NUMBER}"
+              fi
+              # Accept bare semver or leading v (with optional prerelease).
+              if ! echo "$SEMVER" | grep -Eq '^v?[0-9]+\\.[0-9]+\\.[0-9]+(?:[-.][0-9A-Za-z]+)?$'; then
+                SEMVER="0.1.0-${BUILD_NUMBER}"
               fi
               echo "SEMVER=${SEMVER}" > build.env
             '''