diff --git a/.github/scripts/update_generation_config.sh b/.github/scripts/update_generation_config.sh
index 561a31304..91434688c 100644
--- a/.github/scripts/update_generation_config.sh
+++ b/.github/scripts/update_generation_config.sh
@@ -28,11 +28,23 @@ function update_config() {
     sed -i -e "s/^${key_word}.*$/${key_word}: ${new_value}/" "${file}"
 }
 
+# Update an action to a new version in GitHub action.
+function update_action() {
+    local key_word=$1
+    local new_value=$2
+    local file=$3
+    echo "Update ${key_word} to ${new_value} in ${file}"
+    # use a different delimiter because the key_word contains "/".
+    sed -i -e "s|${key_word}@v.*$|${key_word}@v${new_value}|" "${file}"
+}
+
 # The parameters of this script is:
 # 1. base_branch, the base branch of the result pull request.
 # 2. repo, organization/repo-name, e.g., googleapis/google-cloud-java
 # 3. [optional] generation_config, the path to the generation configuration,
 # the default value is generation_config.yaml in the repository root.
+# 4. [optional] workflow, the library generation workflow file,
+# the default value is .github/workflows/hermetic_library_generation.yaml.
 while [[ $# -gt 0 ]]; do
 key="$1"
 case "${key}" in
@@ -48,6 +60,10 @@ case "${key}" in
     generation_config="$2"
     shift
     ;;
+  --workflow)
+    workflow="$2"
+    shift
+    ;;
   *)
     echo "Invalid option: [$1]"
     exit 1
@@ -71,21 +87,34 @@ if [ -z "${generation_config}" ]; then
   echo "Use default generation config: ${generation_config}"
 fi
 
+if [ -z "${workflow}" ]; then
+    workflow=".github/workflows/hermetic_library_generation.yaml"
+    echo "Use default library generation workflow file: ${workflow}"
+fi
+
 current_branch="generate-libraries-${base_branch}"
 title="chore: Update generation configuration at $(date)"
 
-# try to find a open pull request associated with the branch
+git checkout "${base_branch}"
+# Try to find a open pull request associated with the branch
 pr_num=$(gh pr list -s open -H "${current_branch}" -q . --json number | jq ".[] | .number")
-# create a branch if there's no open pull request associated with the
+# Create a branch if there's no open pull request associated with the
 # branch; otherwise checkout the pull request.
 if [ -z "${pr_num}" ]; then
   git checkout -b "${current_branch}"
+  # Push the current branch to remote so that we can
+  # compare the commits later.
+  git push -u origin "${current_branch}"
 else
   gh pr checkout "${pr_num}"
 fi
 
+# Only allow fast-forward merging; exit with non-zero result if there's merging
+# conflict.
+git merge -m "chore: merge ${base_branch} into ${current_branch}" "${base_branch}"
+
 mkdir tmp-googleapis
-# use partial clone because only commit history is needed.
+# Use partial clone because only commit history is needed.
 git clone --filter=blob:none https://github.com/googleapis/googleapis.git tmp-googleapis
 pushd tmp-googleapis
 git pull
@@ -94,25 +123,43 @@ popd
 rm -rf tmp-googleapis
 update_config "googleapis_commitish" "${latest_commit}" "${generation_config}"
 
-# update gapic-generator-java version to the latest
+# Update gapic-generator-java version to the latest
 latest_version=$(get_latest_released_version "com.google.api" "gapic-generator-java")
 update_config "gapic_generator_version" "${latest_version}" "${generation_config}"
 
-# update libraries-bom version to the latest
+# Update composite action version to latest gapic-generator-java version
+update_action "googleapis/sdk-platform-java/.github/scripts" \
+  "${latest_version}" \
+  "${workflow}"
+
+# Update libraries-bom version to the latest
 latest_version=$(get_latest_released_version "com.google.cloud" "libraries-bom")
 update_config "libraries_bom_version" "${latest_version}" "${generation_config}"
 
-git add "${generation_config}"
+git add "${generation_config}" "${workflow}"
 changed_files=$(git diff --cached --name-only)
 if [[ "${changed_files}" == "" ]]; then
     echo "The latest generation config is not changed."
     echo "Skip committing to the pull request."
+else
+    git commit -m "${title}"
+fi
+
+# There are potentially at most two commits: merge commit and change commit.
+# We want to exit the script if no commit happens (otherwise this will be an
+# infinite loop).
+# `git cherry` is a way to find whether the local branch has commits that are
+# not in the remote branch.
+# If we find any such commit, push them to remote branch.
+unpushed_commit=$(git cherry -v "origin/${current_branch}" | wc -l)
+if [[ "${unpushed_commit}" -eq 0 ]]; then
+    echo "No unpushed commits, exit"
     exit 0
 fi
-git commit -m "${title}"
+
 if [ -z "${pr_num}" ]; then
   git remote add remote_repo https://cloud-java-bot:"${GH_TOKEN}@github.com/${repo}.git"
-  git fetch -q --unshallow remote_repo
+  git fetch -q remote_repo
   git push -f remote_repo "${current_branch}"
   gh pr create --title "${title}" --head "${current_branch}" --body "${title}" --base "${base_branch}"
 else