gitlab rules to add a label upon issue change

Is it possible to add a label to a GitLab issue upon issue creation or change? For example:

# .gitlab-ci.yml

job:
  script: echo "Update label."
  rules:
    - if:
        - event: "issue:open"
        - event: "issue:update"
        - not:
          - labels:
            - regexp: "^priority::"
      actions:
        - label: "priority::Medium"

or do GitLab rules not apply to issue events?

As I know there is no ability to do this explicitly. But you can write some kind of custom script which will be triggered by webhook to add labels

Something like that:

import requests
import json

GITLAB_API_URL = "https://gitlab.com/api/{your-version}”
ACCESS_TOKEN = {your_personal_access_token}
PROJECT_ID = {your_project_id}

def add_label_to_issue(issue_id, label):
    url = f"{GITLAB_API_URL}/projects/{PROJECT_ID}/issues/{issue_id}"
    headers = {
        "Private-Token": ACCESS_TOKEN,
        "Content-Type": "application/json"
    }
    data = {
        "labels": label
    }
    response = requests.put(url, headers=headers, data=json.dumps(data))
    if response.status_code == 200:
        print("Label added")
    else:
        print("Failed to add:", response.content)

def handle_issue_event(event_data):
    issue_id = event_data["object_attributes"]["id"]
    current_labels = event_data["labels"]
    if not any(label["title"].startswith("priority::") for label in current_labels):
        add_label_to_issue(issue_id, "priority::Medium")