diff --git a/tests/composition/cmk/piggyback/piggyback_test_helper.py b/tests/composition/cmk/piggyback/piggyback_test_helper.py
index 6f26abda314..b1a1c51b977 100644
--- a/tests/composition/cmk/piggyback/piggyback_test_helper.py
+++ b/tests/composition/cmk/piggyback/piggyback_test_helper.py
@@ -129,12 +129,12 @@ def disable_piggyback_hub_globally(central_site: Site, remote_site_id: str) -> I
         ):
             _write_replication_changes(central_site, central_site.id)
             _write_replication_changes(central_site, remote_site_id)
-            central_site.openapi.activate_changes_and_wait_for_completion()
+            central_site.openapi.changes.activate_and_wait_for_completion()
             yield
     finally:
         _write_replication_changes(central_site, central_site.id)
         _write_replication_changes(central_site, remote_site_id)
-        central_site.openapi.activate_changes_and_wait_for_completion()
+        central_site.openapi.changes.activate_and_wait_for_completion()
 
 
 @contextmanager
@@ -143,11 +143,11 @@ def disable_piggyback_hub_remote_site(central_site: Site, remote_site_id: str) -
         # fake changes to trigger replication
         with _write_sitespecific_config_file(central_site):
             _write_replication_changes(central_site, remote_site_id)
-            central_site.openapi.activate_changes_and_wait_for_completion()
+            central_site.openapi.changes.activate_and_wait_for_completion()
             yield
     finally:
         _write_replication_changes(central_site, remote_site_id)
-        central_site.openapi.activate_changes_and_wait_for_completion()
+        central_site.openapi.changes.activate_and_wait_for_completion()
 
 
 @contextmanager
diff --git a/tests/composition/cmk/piggyback/test_piggyback.py b/tests/composition/cmk/piggyback/test_piggyback.py
index 3bd3b3a2afd..e6730395ac3 100644
--- a/tests/composition/cmk/piggyback/test_piggyback.py
+++ b/tests/composition/cmk/piggyback/test_piggyback.py
@@ -59,11 +59,11 @@ def _setup_piggyback_host(
                 "tag_piggyback": "piggyback",
             },
         )
-        source_site.openapi.activate_changes_and_wait_for_completion()
+        source_site.openapi.changes.activate_and_wait_for_completion()
         yield
     finally:
         source_site.openapi.hosts.delete(hostname_piggyback)
-        source_site.openapi.activate_changes_and_wait_for_completion()
+        source_site.openapi.changes.activate_and_wait_for_completion()
 
 
 @pytest.fixture(name="prepare_piggyback_environment", scope="module")
@@ -83,10 +83,10 @@ def _prepare_piggyback_environment(central_site: Site, remote_site: Site) -> Ite
                 [_HOSTNAME_PIGGYBACKED_B],
             ),
         ):
-            central_site.openapi.activate_changes_and_wait_for_completion()
+            central_site.openapi.changes.activate_and_wait_for_completion()
             yield
     finally:
-        central_site.openapi.activate_changes_and_wait_for_completion()
+        central_site.openapi.changes.activate_and_wait_for_completion()
 
 
 def _schedule_check_and_discover(site: Site, hostname_source: str, hostname_piggyback: str) -> None:
@@ -146,16 +146,16 @@ def _create_and_rename_host(
             },
         )
 
-        source_site.openapi.activate_changes_and_wait_for_completion()
+        source_site.openapi.changes.activate_and_wait_for_completion()
 
         source_site.openapi.hosts.rename_and_wait_for_completion(
             hostname_old="other_host", hostname_new=hostname_piggyback, etag="*"
         )
-        source_site.openapi.activate_changes_and_wait_for_completion()
+        source_site.openapi.changes.activate_and_wait_for_completion()
         yield
     finally:
         source_site.openapi.hosts.delete(hostname_piggyback)
-        source_site.openapi.activate_changes_and_wait_for_completion()
+        source_site.openapi.changes.activate_and_wait_for_completion()
 
 
 def test_piggyback_rename_host(
@@ -210,7 +210,7 @@ def test_piggyback_hub_disabled_globally(
         _schedule_check_and_discover(
             central_site, _HOSTNAME_SOURCE_CENTRAL, _HOSTNAME_PIGGYBACKED_A
         )
-        central_site.openapi.activate_changes_and_wait_for_completion()
+        central_site.openapi.changes.activate_and_wait_for_completion()
 
         assert _piggybacked_service_gets_updated(
             central_site, remote_site, _HOSTNAME_SOURCE_CENTRAL, _HOSTNAME_PIGGYBACKED_A
@@ -245,7 +245,7 @@ def test_piggyback_hub_disabled_remote_site(
         _schedule_check_and_discover(
             central_site, _HOSTNAME_SOURCE_CENTRAL, _HOSTNAME_PIGGYBACKED_A
         )
-        central_site.openapi.activate_changes_and_wait_for_completion()
+        central_site.openapi.changes.activate_and_wait_for_completion()
 
         assert _piggybacked_service_gets_updated(
             central_site, remote_site, _HOSTNAME_SOURCE_CENTRAL, _HOSTNAME_PIGGYBACKED_A
@@ -266,7 +266,7 @@ def _move_host(central_site: Site, to_remote_site: str, hostname_piggyback: str)
         hostname_piggyback,
         update_attributes={"site": to_remote_site},
     )
-    central_site.openapi.activate_changes_and_wait_for_completion()
+    central_site.openapi.changes.activate_and_wait_for_completion()
 
 
 def test_piggyback_services_move_host(
diff --git a/tests/composition/conftest.py b/tests/composition/conftest.py
index d8d556a29dc..8d2f2001b9f 100644
--- a/tests/composition/conftest.py
+++ b/tests/composition/conftest.py
@@ -164,7 +164,7 @@ def _connection(
         }
     )
     central_site.openapi.sites.login(remote_site.id)
-    central_site.openapi.activate_changes_and_wait_for_completion(
+    central_site.openapi.changes.activate_and_wait_for_completion(
         # this seems to be necessary to avoid sporadic CI failures
         force_foreign_changes=True,
     )
@@ -173,7 +173,7 @@ def _connection(
     finally:
         logger.warning("Hosts left: %s", central_site.openapi.hosts.get_all_names())
         central_site.openapi.sites.delete(remote_site.id)
-        central_site.openapi.activate_changes_and_wait_for_completion(
+        central_site.openapi.changes.activate_and_wait_for_completion(
             # this seems to be necessary to avoid sporadic CI failures
             force_foreign_changes=True,
         )
diff --git a/tests/composition/controller_site_interactions/test_proxy_register_import_workflow.py b/tests/composition/controller_site_interactions/test_proxy_register_import_workflow.py
index 3496dff76ad..8cb62282f3d 100644
--- a/tests/composition/controller_site_interactions/test_proxy_register_import_workflow.py
+++ b/tests/composition/controller_site_interactions/test_proxy_register_import_workflow.py
@@ -24,7 +24,7 @@ def test_proxy_register_import_workflow(
 ) -> None:
     hostname = HostName("proxy-host")
     central_site.openapi.hosts.create(hostname=hostname, attributes={"ipaddress": "127.0.0.1"})
-    central_site.openapi.activate_changes_and_wait_for_completion()
+    central_site.openapi.changes.activate_and_wait_for_completion()
 
     try:
         proxy_registration_proc = run(
@@ -56,7 +56,7 @@ def test_proxy_register_import_workflow(
         wait_until_host_receives_data(central_site, hostname)
 
         central_site.openapi.service_discovery.run_discovery_and_wait_for_completion(hostname)
-        central_site.openapi.activate_changes_and_wait_for_completion()
+        central_site.openapi.changes.activate_and_wait_for_completion()
 
         wait_until_host_has_services(
             central_site,
@@ -66,4 +66,4 @@ def test_proxy_register_import_workflow(
         )
     finally:
         central_site.openapi.hosts.delete(hostname=hostname)
-        central_site.openapi.activate_changes_and_wait_for_completion(force_foreign_changes=True)
+        central_site.openapi.changes.activate_and_wait_for_completion(force_foreign_changes=True)
diff --git a/tests/composition/controller_site_interactions/test_register_workflow.py b/tests/composition/controller_site_interactions/test_register_workflow.py
index 83a987462d7..fe03c05b9e9 100644
--- a/tests/composition/controller_site_interactions/test_register_workflow.py
+++ b/tests/composition/controller_site_interactions/test_register_workflow.py
@@ -30,7 +30,7 @@ def _test_register_workflow(
 ) -> None:
     try:
         site.openapi.hosts.create(hostname=hostname, attributes=dict(host_attributes))
-        site.openapi.activate_changes_and_wait_for_completion()
+        site.openapi.changes.activate_and_wait_for_completion()
 
         register_controller(ctl_path, site, hostname)
 
@@ -38,7 +38,7 @@ def _test_register_workflow(
         wait_until_host_receives_data(site, hostname)
 
         site.openapi.service_discovery.run_discovery_and_wait_for_completion(hostname)
-        site.openapi.activate_changes_and_wait_for_completion()
+        site.openapi.changes.activate_and_wait_for_completion()
 
         wait_until_host_has_services(
             site,
@@ -48,7 +48,7 @@ def _test_register_workflow(
         )
     finally:
         site.openapi.hosts.delete(hostname=hostname)
-        site.openapi.activate_changes_and_wait_for_completion(force_foreign_changes=True)
+        site.openapi.changes.activate_and_wait_for_completion(force_foreign_changes=True)
 
 
 @skip_if_not_containerized
diff --git a/tests/composition/controller_site_interactions/test_rename_preserves_registration.py b/tests/composition/controller_site_interactions/test_rename_preserves_registration.py
index 94a40b5c475..8caf7cd37ed 100644
--- a/tests/composition/controller_site_interactions/test_rename_preserves_registration.py
+++ b/tests/composition/controller_site_interactions/test_rename_preserves_registration.py
@@ -32,7 +32,7 @@ def _test_rename_preserves_registration(
                 "site": registration_site.id,
             },
         )
-        central_site.openapi.activate_changes_and_wait_for_completion()
+        central_site.openapi.changes.activate_and_wait_for_completion()
         register_controller(
             ctl_path,
             registration_site,
@@ -53,7 +53,7 @@ def _test_rename_preserves_registration(
         hostnames = set(central_site.openapi.hosts.get_all_names())
         for hostname_ in hostnames.intersection({hostname, new_hostname}):
             central_site.openapi.hosts.delete(hostname_)
-        central_site.openapi.activate_changes_and_wait_for_completion(force_foreign_changes=True)
+        central_site.openapi.changes.activate_and_wait_for_completion(force_foreign_changes=True)
 
 
 @skip_if_not_containerized
diff --git a/tests/composition/controller_site_interactions/test_status.py b/tests/composition/controller_site_interactions/test_status.py
index 501e4e290e9..2b878493b93 100644
--- a/tests/composition/controller_site_interactions/test_status.py
+++ b/tests/composition/controller_site_interactions/test_status.py
@@ -33,13 +33,13 @@ def _get_status_output_json(
 ) -> Iterator[Mapping[str, Any]]:
     try:
         site.openapi.hosts.create(hostname=hostname, attributes=dict(host_attributes))
-        site.openapi.activate_changes_and_wait_for_completion()
+        site.openapi.changes.activate_and_wait_for_completion()
 
         register_controller(ctl_path, site, hostname)
         yield controller_status_json(ctl_path)
     finally:
         site.openapi.hosts.delete(hostname=hostname)
-        site.openapi.activate_changes_and_wait_for_completion(force_foreign_changes=True)
+        site.openapi.changes.activate_and_wait_for_completion(force_foreign_changes=True)
 
 
 @skip_if_not_containerized
diff --git a/tests/composition/message_broker/utils.py b/tests/composition/message_broker/utils.py
index 2b2bef17ef2..a2df3512410 100644
--- a/tests/composition/message_broker/utils.py
+++ b/tests/composition/message_broker/utils.py
@@ -165,8 +165,8 @@ def p2p_connection(central_site: Site, remote_site: Site, remote_site_2: Site) -
         central_site.openapi.broker_connections.create(
             connection_id, connecter=remote_site.id, connectee=remote_site_2.id
         )
-        central_site.openapi.activate_changes_and_wait_for_completion()
+        central_site.openapi.changes.activate_and_wait_for_completion()
         yield
     finally:
         central_site.openapi.broker_connections.delete(connection_id)
-        central_site.openapi.activate_changes_and_wait_for_completion()
+        central_site.openapi.changes.activate_and_wait_for_completion()
diff --git a/tests/composition/test_automatic_host_removal.py b/tests/composition/test_automatic_host_removal.py
index 9e7fe34bf7d..484d5301e70 100644
--- a/tests/composition/test_automatic_host_removal.py
+++ b/tests/composition/test_automatic_host_removal.py
@@ -24,7 +24,7 @@ def test_automatic_host_removal(
     central_site: Site,
     remote_site: Site,
 ) -> None:
-    assert not central_site.openapi.pending_changes()
+    assert not central_site.openapi.changes.get_pending()
 
     unresolvable_host_central = "not-dns-resolvable-central"
     unresolvable_host_remote = "not-dns-resolvable-remote"
@@ -49,7 +49,7 @@ def test_automatic_host_removal(
         },
     )
 
-    central_site.openapi.activate_changes_and_wait_for_completion(force_foreign_changes=True)
+    central_site.openapi.changes.activate_and_wait_for_completion(force_foreign_changes=True)
 
     try:
 
@@ -66,7 +66,7 @@ def _host_removal_done() -> bool:
 
         logger.info("Waiting for changes to be activated")
         wait_until(
-            lambda: not central_site.openapi.pending_changes(),
+            lambda: not central_site.openapi.changes.get_pending(),
             timeout=180,
             interval=20,
         )
@@ -81,4 +81,4 @@ def _host_removal_done() -> bool:
             central_site.openapi.hosts.delete(unresolvable_host_central)
         if unresolvable_host_remote in central_site.openapi.hosts.get_all_names():
             central_site.openapi.hosts.delete(unresolvable_host_remote)
-        central_site.openapi.activate_changes_and_wait_for_completion(force_foreign_changes=True)
+        central_site.openapi.changes.activate_and_wait_for_completion(force_foreign_changes=True)
diff --git a/tests/gui_e2e/conftest.py b/tests/gui_e2e/conftest.py
index ce17b9bd023..18f62cf98fa 100644
--- a/tests/gui_e2e/conftest.py
+++ b/tests/gui_e2e/conftest.py
@@ -245,7 +245,7 @@ def _create_hosts_using_data_from_agent_dump(test_site: Site) -> Iterator:
     test_site.openapi.service_discovery.run_bulk_discovery_and_wait_for_completion(
         created_hosts_list
     )
-    test_site.openapi.activate_changes_and_wait_for_completion()
+    test_site.openapi.changes.activate_and_wait_for_completion()
 
     logger.info("Schedule the 'Check_MK' service")
     for host_name in created_hosts_list:
@@ -258,7 +258,7 @@ def _create_hosts_using_data_from_agent_dump(test_site: Site) -> Iterator:
         logger.info("Clean up: delete the host(s) and the rule")
         test_site.openapi.hosts.bulk_delete(created_hosts_list)
         test_site.openapi.rules.delete(rule_id)
-        test_site.openapi.activate_changes_and_wait_for_completion()
+        test_site.openapi.changes.activate_and_wait_for_completion()
         test_site.delete_dir(test_site_dump_path)
 
 
diff --git a/tests/integration/checks/test_checks_sanity.py b/tests/integration/checks/test_checks_sanity.py
index 3549abead82..a73b9bb599e 100644
--- a/tests/integration/checks/test_checks_sanity.py
+++ b/tests/integration/checks/test_checks_sanity.py
@@ -62,7 +62,7 @@ def _host_services(
         wait_until_host_receives_data(site, hostname)
         wait_for_agent_cache_omd_status(site)
         site.openapi.service_discovery.run_bulk_discovery_and_wait_for_completion([str(hostname)])
-        site.openapi.activate_changes_and_wait_for_completion()
+        site.openapi.changes.activate_and_wait_for_completion()
         if active_mode:
             site.reschedule_services(hostname)
         else:
diff --git a/tests/integration/cmk/ec/test_ec.py b/tests/integration/cmk/ec/test_ec.py
index 49b6f17d97b..b203bc1e31d 100644
--- a/tests/integration/cmk/ec/test_ec.py
+++ b/tests/integration/cmk/ec/test_ec.py
@@ -111,7 +111,7 @@ def _write_ec_rule(site: Site, rule: list | None) -> None:
 def _activate_ec_changes(site: Site) -> None:
     replication_changes_path = site.path(f"var/check_mk/wato/replication_changes_{site.id}.mk")
     site.write_text_file(str(replication_changes_path), str(_get_replication_change()))
-    site.openapi.activate_changes_and_wait_for_completion(force_foreign_changes=True)
+    site.openapi.changes.activate_and_wait_for_completion(force_foreign_changes=True)
 
 
 def _generate_message_via_events_pipe(site: Site, message: str, end_of_line: bool = True) -> None:
diff --git a/tests/integration/core/test_core_switch.py b/tests/integration/core/test_core_switch.py
index 317f82ee23c..a6e11a7be02 100644
--- a/tests/integration/core/test_core_switch.py
+++ b/tests/integration/core/test_core_switch.py
@@ -51,11 +51,11 @@ def test_core_switch(site: Site, switch_core: Iterator[None]) -> None:
         site.openapi.hosts.create(
             "test_host_core_switch", attributes={"ipaddress": site.http_address, "site": site.id}
         )
-        site.openapi.activate_changes_and_wait_for_completion()
+        site.openapi.changes.activate_and_wait_for_completion()
     except Exception as e:
         logger.error(e)
         raise
 
     finally:
         site.openapi.hosts.delete("test_host_core_switch")
-        site.openapi.activate_changes_and_wait_for_completion()
+        site.openapi.changes.activate_and_wait_for_completion()
diff --git a/tests/plugins_integration/checks.py b/tests/plugins_integration/checks.py
index a1ea75bdd23..3c3b0c6293e 100644
--- a/tests/plugins_integration/checks.py
+++ b/tests/plugins_integration/checks.py
@@ -635,9 +635,7 @@ def wait_for_dcd_pend_changes(site: Site) -> None:
     """Wait up to 60 seconds for DCD to activate changes."""
     max_count = 60
     count = 0
-    while (
-        n_pending_changes := len(site.openapi.pending_changes([site.id]))
-    ) > 0 and count < max_count:
+    while (n_pending_changes := len(site.openapi.changes.get_pending())) > 0 and count < max_count:
         logger.info(
             "Waiting for changes to be activated by the DCD connector. Count: %s/%s",
             count,
@@ -668,12 +666,12 @@ def _dcd_connector(test_site_piggyback: Site) -> Iterator[None]:
         delete_hosts=True,
         no_deletion_time_after_init=60,
     )
-    test_site_piggyback.openapi.activate_changes_and_wait_for_completion(force_foreign_changes=True)
+    test_site_piggyback.openapi.changes.activate_and_wait_for_completion(force_foreign_changes=True)
     try:
         yield
     finally:
         if not config.skip_cleanup:
             test_site_piggyback.openapi.dcd.delete(dcd_id)
-            test_site_piggyback.openapi.activate_changes_and_wait_for_completion(
+            test_site_piggyback.openapi.changes.activate_and_wait_for_completion(
                 force_foreign_changes=True
             )
diff --git a/tests/plugins_integration/conftest.py b/tests/plugins_integration/conftest.py
index d757aedfa1d..bbc3f57d986 100644
--- a/tests/plugins_integration/conftest.py
+++ b/tests/plugins_integration/conftest.py
@@ -286,11 +286,11 @@ def _create_periodic_service_discovery_rule(test_site_update: Site) -> Iterator[
         ruleset_name="periodic_discovery",
         value=_periodic_service_discovery_rule(),
     )
-    test_site_update.openapi.activate_changes_and_wait_for_completion()
+    test_site_update.openapi.changes.activate_and_wait_for_completion()
 
     yield
 
     for rule in test_site_update.openapi.rules.get_all("periodic_discovery"):
         if rule["id"] not in existing_rules_ids:
             test_site_update.openapi.rules.delete(rule["id"])
-    test_site_update.openapi.activate_changes_and_wait_for_completion()
+    test_site_update.openapi.changes.activate_and_wait_for_completion()
diff --git a/tests/testlib/agent.py b/tests/testlib/agent.py
index 441c5ec95ff..79b8981db08 100644
--- a/tests/testlib/agent.py
+++ b/tests/testlib/agent.py
@@ -381,4 +381,4 @@ def clean_up_host(site: Site, hostname: HostName) -> Iterator[None]:
             deleted = True
 
         if deleted:
-            site.openapi.activate_changes_and_wait_for_completion(force_foreign_changes=True)
+            site.openapi.changes.activate_and_wait_for_completion(force_foreign_changes=True)
diff --git a/tests/testlib/emails.py b/tests/testlib/emails.py
index c18279002e1..31e551d2fbc 100644
--- a/tests/testlib/emails.py
+++ b/tests/testlib/emails.py
@@ -170,7 +170,7 @@ def create_notification_user(site: Site, admin: bool = False) -> Iterator[tuple[
         customer="global" if site.version.is_managed_edition() else None,
         roles=["admin"] if admin else [],
     )
-    site.openapi.activate_changes_and_wait_for_completion()
+    site.openapi.changes.activate_and_wait_for_completion()
     yield user_name, email_address
     site.openapi.users.delete(user_name)
-    site.openapi.activate_changes_and_wait_for_completion()
+    site.openapi.changes.activate_and_wait_for_completion()
diff --git a/tests/testlib/openapi_session.py b/tests/testlib/openapi_session.py
index 68646c057a7..fade2eeb545 100644
--- a/tests/testlib/openapi_session.py
+++ b/tests/testlib/openapi_session.py
@@ -108,6 +108,7 @@ def __init__(
         self.headers["Accept"] = "application/json"
         self.set_authentication_header(user, password)
 
+        self.changes = ChangesAPI(self)
         self.users = UsersAPI(self)
         self.folders = FoldersAPI(self)
         self.hosts = HostsAPI(self)
@@ -169,75 +170,6 @@ def request(  # type: ignore[no-untyped-def]
 
         return response
 
-    def activate_changes(
-        self,
-        sites: list[str] | None = None,
-        force_foreign_changes: bool = False,
-    ) -> None:
-        response = self.post(
-            "/domain-types/activation_run/actions/activate-changes/invoke",
-            json={
-                "redirect": True,
-                "sites": sites or [],
-                "force_foreign_changes": force_foreign_changes,
-            },
-            headers={"If-Match": "*"},
-            # We want to get the redirect response and handle that below. So don't let requests
-            # handle that for us.
-            allow_redirects=False,
-        )
-        if response.status_code == 200:
-            logger.info("Activation id: %s", response.json()["id"])
-            return  # changes are activated
-        if response.status_code == 422:
-            raise NoActiveChanges  # there are no changes
-        if 300 <= response.status_code < 400:
-            redirect_url = response.headers["Location"]
-
-            # Extract the activation ID from the wait-for-completion URL
-            # "/{site_id}/check_mk/api/1.0/objects/activation_run/{activation_id}/actions/wait-for-completion/invoke",
-            assert redirect_url.split("/")[6] == "activation_run"
-            activation_id = redirect_url.split("/")[7]
-            logger.info("Activation pending (ID: %s)", activation_id)
-
-            raise Redirect(redirect_url=redirect_url)  # activation pending
-        raise UnexpectedResponse.from_response(response)
-
-    def pending_changes(self, sites: list[str] | None = None) -> list[dict[str, Any]]:
-        """Returns a list of all changes currently pending."""
-        response = self.get("/domain-types/activation_run/collections/pending_changes")
-        assert response.status_code == 200
-        value: list[dict[str, Any]] = response.json()["value"]
-        return value
-
-    @tracer.start_as_current_span("activate_changes_and_wait_for_completion")
-    def activate_changes_and_wait_for_completion(
-        self,
-        sites: list[str] | None = None,
-        force_foreign_changes: bool = False,
-        timeout: int = 300,  # TODO: revert to 60 seconds once performance is improved.
-    ) -> bool:
-        """Activate changes via REST API and wait for completion.
-
-        Returns:
-            * True if changes are activated
-            * False if there are no changes to be activated
-        """
-        logger.info("Activate changes and wait %ds for completion...", timeout)
-        with self.wait_for_completion(timeout, "get", "activate_changes"):
-            try:
-                self.activate_changes(sites, force_foreign_changes)
-            except NoActiveChanges:
-                logger.info("There were no changes to activate")
-                return False
-
-        pending_changes = self.pending_changes()
-        assert (
-            not pending_changes
-        ), f"There are pending changes that were not activated: {pending_changes}"
-
-        return True
-
     @contextmanager
     def wait_for_completion(
         self,
@@ -306,6 +238,68 @@ def __init__(self, session: CMKOpenApiSession) -> None:
         self.session = session
 
 
+class ChangesAPI(BaseAPI):
+    def activate(
+        self,
+        sites: list[str] | None = None,
+        force_foreign_changes: bool = False,
+    ) -> None:
+        response = self.session.post(
+            "/domain-types/activation_run/actions/activate-changes/invoke",
+            json={
+                "redirect": True,
+                "sites": sites or [],
+                "force_foreign_changes": force_foreign_changes,
+            },
+            headers={"If-Match": "*"},
+            # We want to get the redirect response and handle that below. So don't let requests
+            # handle that for us.
+            allow_redirects=False,
+        )
+        if response.status_code == 200:
+            logger.info("Activation id: %s", response.json()["id"])
+            return  # changes are activated
+        if response.status_code == 422:
+            raise NoActiveChanges  # there are no changes
+        if 300 <= response.status_code < 400:
+            raise Redirect(redirect_url=response.headers["Location"])  # activation pending
+        raise UnexpectedResponse.from_response(response)
+
+    def get_pending(self) -> list[dict[str, Any]]:
+        """Returns a list of all changes currently pending."""
+        response = self.session.get("/domain-types/activation_run/collections/pending_changes")
+        assert response.status_code == 200
+        value: list[dict[str, Any]] = response.json()["value"]
+        return value
+
+    @tracer.start_as_current_span("activate_and_wait_for_completion")
+    def activate_and_wait_for_completion(
+        self,
+        sites: list[str] | None = None,
+        force_foreign_changes: bool = False,
+        timeout: int = 300,  # TODO: revert to 60 seconds once performance is improved.
+    ) -> bool:
+        """Activate changes via REST API and wait for completion.
+
+        Returns:
+            * True if changes are activated
+            * False if there are no changes to be activated
+        """
+        logger.info("Activate changes and wait %ds for completion...", timeout)
+        with self.session.wait_for_completion(timeout, "get", "activate_changes"):
+            try:
+                self.activate(sites, force_foreign_changes)
+            except NoActiveChanges:
+                return False
+
+        pending_changes = self.get_pending()
+        assert (
+            not pending_changes
+        ), f"There are pending changes that were not activated: {pending_changes}"
+
+        return True
+
+
 class UsersAPI(BaseAPI):
     def create(
         self,
diff --git a/tests/testlib/site.py b/tests/testlib/site.py
index 42c0097fd7a..2d233191366 100644
--- a/tests/testlib/site.py
+++ b/tests/testlib/site.py
@@ -1412,7 +1412,7 @@ def activate_changes_and_wait_for_core_reload(
                             "A previous activation is still running. Does the wait work?"
                         )
 
-            changed = self.openapi.activate_changes_and_wait_for_completion(
+            changed = self.openapi.changes.activate_and_wait_for_completion(
                 force_foreign_changes=allow_foreign_changes
             )
             if changed:
@@ -1777,7 +1777,7 @@ def update_as_site_user(
             site.version.edition.short == target_version.edition.short
         ), "Edition mismatch during update!"
 
-        site.openapi.activate_changes_and_wait_for_completion()
+        site.openapi.changes.activate_and_wait_for_completion()
 
         return site