First try at making the TLS registration idempotent.

roles/agent/tasks/Linux.yml

@@ -87,6 +87,11 @@
     path: /usr/bin/cmk-agent-ctl
   register: __checkmk_agent_controller_binary
 
+- name: "{{ ansible_system }}: Read Agent Controller State."  # noqa no-changed-when
+  become: true
+  ansible.builtin.command: cat /var/lib/cmk-agent/registered_connections.json
+  register: __checkmk_agent_registered_connections
+
 - name: "{{ ansible_system }}: Register Agent for automatic Updates using User Password."  # noqa no-changed-when
   become: true
   ansible.builtin.shell: |
@@ -128,6 +133,7 @@
     __checkmk_agent_controller_binary.stat.exists | bool
     and checkmk_agent_tls | bool
     and (__checkmk_agent_auth is defined and __checkmk_agent_auth | length)
+    and not checkmk_agent_registration_server + '/' + checkmk_agent_registration_site in __checkmk_agent_registered_connections.stdout
 
 - name: "{{ ansible_system }}: Verify Checkmk Agent Port is open."
   ansible.builtin.wait_for: