diff --git a/group_vars/matrix_servers b/group_vars/matrix_servers
index a237e0b0d..5ece91a09 100755
--- a/group_vars/matrix_servers
+++ b/group_vars/matrix_servers
@@ -247,6 +247,78 @@ matrix_homeserver_app_service_config_files_auto: |
     (['/matrix-steam-bridge-registration.yaml'] if matrix_bridge_steam_enabled else [])
   }}
 
+# Tells whether any appservice registration file mounted into the homeserver (see `matrix_homeserver_container_extra_arguments_auto`)
+# changed during this run, so that the homeserver is restarted to pick it up.
+# Each entry is the registered result of the task which installs that file.
+# Synapse workers read the same configuration and registration files as the main Synapse process,
+# so their entries in `devture_systemd_service_manager_services_list_auto` follow the same restart decision.
+matrix_homeserver_app_service_registration_changed: |
+  {{
+    (
+      ([matrix_bridge_appservice_discord_registration_result | default({})] if matrix_bridge_appservice_discord_enabled else [])
+      +
+      ([matrix_appservice_draupnir_for_all_registration_config_result | default({})] if matrix_appservice_draupnir_for_all_enabled else [])
+      +
+      ([matrix_bot_meowlnir_registration_result | default({})] if matrix_bot_meowlnir_enabled else [])
+      +
+      ([matrix_appservice_double_puppet_registration_result | default({})] if matrix_appservice_double_puppet_enabled else [])
+      +
+      ([matrix_bridge_appservice_irc_registration_result | default({})] if matrix_bridge_appservice_irc_enabled else [])
+      +
+      ([matrix_bridge_beeper_linkedin_registration_result | default({})] if matrix_bridge_beeper_linkedin_enabled else [])
+      +
+      ([matrix_bridge_beeper_line_registration_result | default({})] if matrix_bridge_beeper_line_enabled else [])
+      +
+      ([matrix_bridge_wechat_registration_result | default({})] if matrix_bridge_wechat_enabled else [])
+      +
+      ([matrix_bridge_heisenbridge_registration_result | default({})] if matrix_bridge_heisenbridge_enabled else [])
+      +
+      ([matrix_bridge_hookshot_registration_result | default({})] if matrix_bridge_hookshot_enabled else [])
+      +
+      ([matrix_bridge_mautrix_bluesky_registration_result | default({})] if matrix_bridge_mautrix_bluesky_enabled else [])
+      +
+      ([matrix_bridge_rustpush_registration_result | default({})] if matrix_bridge_rustpush_enabled else [])
+      +
+      ([matrix_bridge_mautrix_discord_registration_result | default({})] if matrix_bridge_mautrix_discord_enabled else [])
+      +
+      ([matrix_bridge_mautrix_slack_registration_result | default({})] if matrix_bridge_mautrix_slack_enabled else [])
+      +
+      ([matrix_bridge_mautrix_googlechat_registration_result | default({})] if matrix_bridge_mautrix_googlechat_enabled else [])
+      +
+      ([matrix_bridge_mautrix_signal_registration_result | default({})] if matrix_bridge_mautrix_signal_enabled else [])
+      +
+      ([matrix_bridge_mautrix_meta_messenger_registration_result | default({})] if matrix_bridge_mautrix_meta_messenger_enabled else [])
+      +
+      ([matrix_bridge_mautrix_meta_instagram_registration_result | default({})] if matrix_bridge_mautrix_meta_instagram_enabled else [])
+      +
+      ([matrix_bridge_mautrix_telegram_registration_result | default({})] if matrix_bridge_mautrix_telegram_enabled else [])
+      +
+      ([matrix_bridge_mautrix_twitter_registration_result | default({})] if matrix_bridge_mautrix_twitter_enabled else [])
+      +
+      ([matrix_bridge_mautrix_gmessages_registration_result | default({})] if matrix_bridge_mautrix_gmessages_enabled else [])
+      +
+      ([matrix_bridge_mautrix_gvoice_registration_result | default({})] if matrix_bridge_mautrix_gvoice_enabled else [])
+      +
+      ([matrix_bridge_mautrix_linkedin_registration_result | default({})] if matrix_bridge_mautrix_linkedin_enabled else [])
+      +
+      ([matrix_bridge_mautrix_whatsapp_registration_result | default({})] if matrix_bridge_mautrix_whatsapp_enabled else [])
+      +
+      ([matrix_bridge_mautrix_wsproxy_registration_androidsms_result | default({})] if matrix_bridge_mautrix_wsproxy_enabled else [])
+      +
+      ([matrix_bridge_mautrix_wsproxy_registration_imessage_result | default({})] if matrix_bridge_mautrix_wsproxy_enabled else [])
+      +
+      ([matrix_bridge_mx_puppet_groupme_registration_result | default({})] if matrix_bridge_mx_puppet_groupme_enabled else [])
+      +
+      ([matrix_bridge_mx_puppet_steam_registration_result | default({})] if matrix_bridge_mx_puppet_steam_enabled else [])
+      +
+      ([matrix_bridge_sms_registration_result | default({})] if matrix_bridge_sms_enabled else [])
+      +
+      ([matrix_bridge_steam_registration_result | default({})] if matrix_bridge_steam_enabled else [])
+      +
+      ([matrix_cactus_comments_config_appservice_result | default({})] if matrix_cactus_comments_enabled else [])
+    ) | selectattr('changed', 'defined') | selectattr('changed') | list | length > 0
+  }}
+
 matrix_addons_homeserver_container_network: "{{ matrix_playbook_reverse_proxy_container_network if matrix_playbook_internal_matrix_client_api_traefik_entrypoint_enabled else matrix_homeserver_container_network }}"
 matrix_addons_homeserver_client_api_url: "{{ ('http://' + matrix_playbook_reverse_proxy_hostname + ':' + matrix_playbook_internal_matrix_client_api_traefik_entrypoint_port | string) if matrix_playbook_internal_matrix_client_api_traefik_entrypoint_enabled else matrix_homeserver_container_url }}"
 matrix_addons_homeserver_systemd_services_list: |
@@ -681,6 +753,7 @@ devture_systemd_service_manager_services_list_auto: |
         else (matrix_continuwuity_restart_necessary | bool) if matrix_homeserver_implementation == 'continuwuity'
         else (matrix_tuwunel_restart_necessary | bool) if matrix_homeserver_implementation == 'tuwunel'
         else (matrix_dendrite_restart_necessary | bool) if matrix_homeserver_implementation == 'dendrite'
+        else ((matrix_synapse_restart_necessary | bool) or (matrix_homeserver_app_service_registration_changed | bool)) if matrix_homeserver_implementation == 'synapse'
         else true
       ),
       'groups': ['matrix', 'homeservers', matrix_homeserver_implementation],
@@ -959,7 +1032,7 @@ devture_systemd_service_manager_services_list_auto: |
       'groups': ['matrix', 'traefik-certs-dumper'],
     }] if traefik_certs_dumper_enabled else [])
     +
-    (matrix_synapse_worker_systemd_services_list if matrix_synapse_enabled else [])
+    (matrix_synapse_worker_systemd_services_list | map('combine', {'restart_necessary': ((matrix_synapse_restart_necessary | bool) or (matrix_homeserver_app_service_registration_changed | bool))}) | list if matrix_synapse_enabled else [])
   }}
 
 ########################################################################
diff --git a/roles/custom/matrix-appservice-double-puppet/tasks/install.yml b/roles/custom/matrix-appservice-double-puppet/tasks/install.yml
index 385805d19..220723cce 100644
--- a/roles/custom/matrix-appservice-double-puppet/tasks/install.yml
+++ b/roles/custom/matrix-appservice-double-puppet/tasks/install.yml
@@ -25,3 +25,4 @@
     mode: '0644'
     owner: "{{ matrix_user_name }}"
     group: "{{ matrix_group_name }}"
+  register: matrix_appservice_double_puppet_registration_result
diff --git a/roles/custom/matrix-synapse/defaults/main.yml b/roles/custom/matrix-synapse/defaults/main.yml
index dbe53c0c1..0e84099a7 100644
--- a/roles/custom/matrix-synapse/defaults/main.yml
+++ b/roles/custom/matrix-synapse/defaults/main.yml
@@ -135,6 +135,18 @@ matrix_synapse_ext_s3_storage_provider_container_arguments: []
 # installation tasks haven't run (e.g., due to --tags skipping them).
 matrix_synapse_s3_storage_provider_restart_necessary: false
 
+# matrix_synapse_restart_necessary controls whether Synapse and its workers
+# will be restarted (when true) or merely started (when false) by the
+# systemd service manager role (when conditional restart is enabled).
+#
+# This value is automatically computed during installation based on whether
+# the Synapse or worker configuration, support files, systemd service files,
+# container image or extension modules changed.
+# The playbook also restarts Synapse when an appservice registration file it mounts changes.
+# The default of `false` means "no restart needed" — appropriate when the role's
+# installation tasks haven't run (e.g., due to --tags skipping them).
+matrix_synapse_restart_necessary: false
+
 matrix_synapse_container_client_api_port: 8008
 
 # Controls the `x_forwarded` setting for the "Insecure HTTP listener (Client API)".
diff --git a/roles/custom/matrix-synapse/tasks/ext/encryption-disabler/setup_install.yml b/roles/custom/matrix-synapse/tasks/ext/encryption-disabler/setup_install.yml
index b3d79f283..7fcb5f6fe 100644
--- a/roles/custom/matrix-synapse/tasks/ext/encryption-disabler/setup_install.yml
+++ b/roles/custom/matrix-synapse/tasks/ext/encryption-disabler/setup_install.yml
@@ -13,10 +13,10 @@
     mode: '0440'
     owner: "{{ matrix_synapse_uid }}"
     group: "{{ matrix_synapse_gid }}"
-  register: result
+  register: matrix_synapse_ext_encryption_disabler_download_result
   retries: "{{ devture_playbook_help_geturl_retries_count }}"
   delay: "{{ devture_playbook_help_geturl_retries_delay }}"
-  until: result is not failed
+  until: matrix_synapse_ext_encryption_disabler_download_result is not failed
 
 - ansible.builtin.set_fact:
     matrix_synapse_modules: |
diff --git a/roles/custom/matrix-synapse/tasks/ext/mjolnir-antispam/setup_install.yml b/roles/custom/matrix-synapse/tasks/ext/mjolnir-antispam/setup_install.yml
index 5e4c1b224..41e6277ca 100644
--- a/roles/custom/matrix-synapse/tasks/ext/mjolnir-antispam/setup_install.yml
+++ b/roles/custom/matrix-synapse/tasks/ext/mjolnir-antispam/setup_install.yml
@@ -34,6 +34,7 @@
     GIT_CONFIG_COUNT: "1"
     GIT_CONFIG_KEY_0: safe.directory
     GIT_CONFIG_VALUE_0: "{{ matrix_synapse_ext_path }}/mjolnir"
+  register: matrix_synapse_ext_spam_checker_mjolnir_antispam_git_result
 
 - ansible.builtin.set_fact:
     matrix_synapse_modules: >
diff --git a/roles/custom/matrix-synapse/tasks/ext/rest-auth/setup_install.yml b/roles/custom/matrix-synapse/tasks/ext/rest-auth/setup_install.yml
index 4df5d68ba..a13b2389a 100644
--- a/roles/custom/matrix-synapse/tasks/ext/rest-auth/setup_install.yml
+++ b/roles/custom/matrix-synapse/tasks/ext/rest-auth/setup_install.yml
@@ -20,10 +20,10 @@
     mode: '0440'
     owner: "{{ matrix_synapse_uid }}"
     group: "{{ matrix_synapse_gid }}"
-  register: result
+  register: matrix_synapse_ext_password_provider_rest_auth_download_result
   retries: "{{ devture_playbook_help_geturl_retries_count }}"
   delay: "{{ devture_playbook_help_geturl_retries_delay }}"
-  until: result is not failed
+  until: matrix_synapse_ext_password_provider_rest_auth_download_result is not failed
 
 - ansible.builtin.set_fact:
     matrix_synapse_password_providers_enabled: true
diff --git a/roles/custom/matrix-synapse/tasks/ext/shared-secret-auth/setup_install.yml b/roles/custom/matrix-synapse/tasks/ext/shared-secret-auth/setup_install.yml
index 71198c84c..5d121b55b 100644
--- a/roles/custom/matrix-synapse/tasks/ext/shared-secret-auth/setup_install.yml
+++ b/roles/custom/matrix-synapse/tasks/ext/shared-secret-auth/setup_install.yml
@@ -25,10 +25,10 @@
     mode: '0440'
     owner: "{{ matrix_synapse_uid }}"
     group: "{{ matrix_synapse_gid }}"
-  register: result
+  register: matrix_synapse_ext_password_provider_shared_secret_auth_download_result
   retries: "{{ devture_playbook_help_geturl_retries_count }}"
   delay: "{{ devture_playbook_help_geturl_retries_delay }}"
-  until: result is not failed
+  until: matrix_synapse_ext_password_provider_shared_secret_auth_download_result is not failed
 
 - ansible.builtin.set_fact:
     matrix_synapse_modules: |
diff --git a/roles/custom/matrix-synapse/tasks/ext/synapse-http-antispam/setup_install.yml b/roles/custom/matrix-synapse/tasks/ext/synapse-http-antispam/setup_install.yml
index 88e44b480..6e6bf9265 100644
--- a/roles/custom/matrix-synapse/tasks/ext/synapse-http-antispam/setup_install.yml
+++ b/roles/custom/matrix-synapse/tasks/ext/synapse-http-antispam/setup_install.yml
@@ -32,6 +32,7 @@
     GIT_CONFIG_COUNT: "1"
     GIT_CONFIG_KEY_0: safe.directory
     GIT_CONFIG_VALUE_0: "{{ matrix_synapse_ext_path }}/synapse-http-antispam"
+  register: matrix_synapse_ext_synapse_http_antispam_git_result
 
 - ansible.builtin.set_fact:
     matrix_synapse_modules: >
diff --git a/roles/custom/matrix-synapse/tasks/ext/synapse-simple-antispam/setup_install.yml b/roles/custom/matrix-synapse/tasks/ext/synapse-simple-antispam/setup_install.yml
index f45ec1917..4d405301e 100644
--- a/roles/custom/matrix-synapse/tasks/ext/synapse-simple-antispam/setup_install.yml
+++ b/roles/custom/matrix-synapse/tasks/ext/synapse-simple-antispam/setup_install.yml
@@ -41,6 +41,7 @@
     GIT_CONFIG_COUNT: "1"
     GIT_CONFIG_KEY_0: safe.directory
     GIT_CONFIG_VALUE_0: "{{ matrix_synapse_ext_path }}/synapse-simple-antispam"
+  register: matrix_synapse_ext_spam_checker_synapse_simple_antispam_git_result
 
 - ansible.builtin.set_fact:
     matrix_synapse_modules: >
diff --git a/roles/custom/matrix-synapse/tasks/synapse/setup_install.yml b/roles/custom/matrix-synapse/tasks/synapse/setup_install.yml
index 4f0926ead..4527a6f48 100644
--- a/roles/custom/matrix-synapse/tasks/synapse/setup_install.yml
+++ b/roles/custom/matrix-synapse/tasks/synapse/setup_install.yml
@@ -79,16 +79,17 @@
         DOCKER_BUILDKIT: 1
       changed_when: true
       when: "matrix_synapse_git_pull_results.changed | bool or matrix_synapse_container_image_check_result.stdout == ''"
+      register: matrix_synapse_container_image_build_result
 
 - name: Ensure Synapse Docker image is pulled
   community.docker.docker_image_pull:
     name: "{{ matrix_synapse_container_image }}"
     pull: always
   when: "not matrix_synapse_container_image_self_build"
-  register: result
+  register: matrix_synapse_container_image_pull_result
   retries: "{{ devture_playbook_help_container_retries_count }}"
   delay: "{{ devture_playbook_help_container_retries_delay }}"
-  until: result is not failed
+  until: matrix_synapse_container_image_pull_result is not failed
 
 - when: "matrix_synapse_container_image_customizations_enabled | bool"
   block:
@@ -133,6 +134,7 @@
       {{ matrix_synapse_container_image }}
       generate
     creates: "{{ matrix_synapse_config_dir_path }}/{{ matrix_server_fqn_matrix }}.signing.key"
+  register: matrix_synapse_initial_config_result
 
 - name: Ensure Synapse homeserver config installed
   ansible.builtin.copy:
@@ -141,6 +143,7 @@
     mode: '0644'
     owner: "{{ matrix_synapse_uid }}"
     group: "{{ matrix_synapse_gid }}"
+  register: matrix_synapse_config_result
 
 - name: Ensure Synapse container network is created
   when: matrix_synapse_container_network != 'host'
@@ -168,6 +171,7 @@
     - src: "{{ role_path }}/templates/synapse/systemd/matrix-synapse.service.j2"
       dest: "{{ devture_systemd_docker_base_systemd_path }}/matrix-synapse.service"
       mode: '0644'
+  register: matrix_synapse_support_files_result
 
 - name: Generate sample prometheus.yml for external scraping
   ansible.builtin.template:
@@ -177,3 +181,22 @@
     group: "{{ matrix_synapse_gid }}"
     mode: '0644'
   when: matrix_synapse_metrics_proxying_enabled | bool
+
+- name: Determine whether Synapse needs a restart
+  ansible.builtin.set_fact:
+    matrix_synapse_restart_necessary: >-
+      {{
+        matrix_synapse_config_result.changed | default(false)
+        or matrix_synapse_initial_config_result.changed | default(false)
+        or matrix_synapse_support_files_result.changed | default(false)
+        or matrix_synapse_container_image_pull_result.changed | default(false)
+        or matrix_synapse_container_image_build_result.changed | default(false)
+        or matrix_synapse_container_image_customized_build_result.changed | default(false)
+        or matrix_synapse_workers_files_changed | default(false) | bool
+        or matrix_synapse_ext_encryption_disabler_download_result.changed | default(false)
+        or matrix_synapse_ext_password_provider_rest_auth_download_result.changed | default(false)
+        or matrix_synapse_ext_password_provider_shared_secret_auth_download_result.changed | default(false)
+        or matrix_synapse_ext_spam_checker_mjolnir_antispam_git_result.changed | default(false)
+        or matrix_synapse_ext_spam_checker_synapse_simple_antispam_git_result.changed | default(false)
+        or matrix_synapse_ext_synapse_http_antispam_git_result.changed | default(false)
+      }}
diff --git a/roles/custom/matrix-synapse/tasks/synapse/workers/util/setup_files_for_worker.yml b/roles/custom/matrix-synapse/tasks/synapse/workers/util/setup_files_for_worker.yml
index d6c55fb25..e731da24f 100644
--- a/roles/custom/matrix-synapse/tasks/synapse/workers/util/setup_files_for_worker.yml
+++ b/roles/custom/matrix-synapse/tasks/synapse/workers/util/setup_files_for_worker.yml
@@ -20,6 +20,7 @@
     mode: '0644'
     owner: "{{ matrix_synapse_uid }}"
     group: "{{ matrix_synapse_gid }}"
+  register: matrix_synapse_worker_config_result
 
 - name: Ensure labels exists for {{ matrix_synapse_worker_systemd_service_name }}
   ansible.builtin.template:
@@ -28,9 +29,22 @@
     mode: '0644'
     owner: "{{ matrix_synapse_uid }}"
     group: "{{ matrix_synapse_gid }}"
+  register: matrix_synapse_worker_labels_result
 
 - name: Ensure systemd service exists for {{ matrix_synapse_worker_systemd_service_name }}
   ansible.builtin.template:
     src: "{{ role_path }}/templates/synapse/systemd/matrix-synapse-worker.service.j2"
     dest: "{{ devture_systemd_docker_base_systemd_path }}/{{ matrix_synapse_worker_systemd_service_name }}.service"
     mode: '0644'
+  register: matrix_synapse_worker_systemd_service_result
+
+# Workers share Synapse's restart decision (see `matrix_synapse_restart_necessary`),
+# so a change to any one worker's files marks it as needed.
+- ansible.builtin.set_fact:
+    matrix_synapse_workers_files_changed: >-
+      {{
+        matrix_synapse_workers_files_changed | default(false) | bool
+        or matrix_synapse_worker_config_result.changed | default(false)
+        or matrix_synapse_worker_labels_result.changed | default(false)
+        or matrix_synapse_worker_systemd_service_result.changed | default(false)
+      }}