diff --git a/localizers/easynav_fusion_localizer/package.xml b/localizers/easynav_fusion_localizer/package.xml
index 5cc4358e..8ca41f1a 100644
--- a/localizers/easynav_fusion_localizer/package.xml
+++ b/localizers/easynav_fusion_localizer/package.xml
@@ -37,6 +37,7 @@
   <test_depend>ament_lint_auto</test_depend>
   <test_depend>ament_lint_common</test_depend>
   <test_depend>robot_localization</test_depend>
+  <test_depend>rosgraph_msgs</test_depend>
 
   <export>
     <build_type>ament_cmake</build_type>
diff --git a/localizers/easynav_fusion_localizer/src/easynav_fusion_localizer/ukf_wrapper.cpp b/localizers/easynav_fusion_localizer/src/easynav_fusion_localizer/ukf_wrapper.cpp
index 0b80da65..4e2f1a90 100644
--- a/localizers/easynav_fusion_localizer/src/easynav_fusion_localizer/ukf_wrapper.cpp
+++ b/localizers/easynav_fusion_localizer/src/easynav_fusion_localizer/ukf_wrapper.cpp
@@ -2313,9 +2313,23 @@ void UkfWrapper::poseCallback(
 
 void UkfWrapper::initialize()
 {
-  if (!parent_node_->get_clock()->started()) {
-    RCLCPP_INFO(parent_node_->get_logger(), "Waiting for clock to start...");
-    parent_node_->get_clock()->wait_until_started();
+  // With use_sim_time and no /clock this blocks the configuration of every EasyNav node: say
+  // so until it starts, and stop waiting if rclcpp is shut down (a second signal)
+  const auto context = parent_node_->get_node_base_interface()->get_context();
+  const rclcpp::Duration step = rclcpp::Duration::from_seconds(5.0);
+  auto started = [&]() {
+      try {
+        return parent_node_->get_clock()->wait_until_started(step, context);
+      } catch (const std::runtime_error &) {
+        return false;  // the context was shut down
+      }
+    };
+  double waited = 0.0;
+  while (rclcpp::ok(context) && !started() && rclcpp::ok(context)) {
+    waited += step.seconds();
+    RCLCPP_WARN(
+      parent_node_->get_logger(), "Waiting for the ROS clock to start (%.0f s): use_sim_time is "
+      "true and no /clock reaches this node. EasyNav does not configure until it does", waited);
   }
 
   angular_acceleration_.setZero();
diff --git a/localizers/easynav_fusion_localizer/tests/CMakeLists.txt b/localizers/easynav_fusion_localizer/tests/CMakeLists.txt
index bdbeca1c..6cc4e0ed 100644
--- a/localizers/easynav_fusion_localizer/tests/CMakeLists.txt
+++ b/localizers/easynav_fusion_localizer/tests/CMakeLists.txt
@@ -26,3 +26,12 @@ target_link_libraries(fusion_localizer_local_filter_tests
   rclcpp::rclcpp
   easynav_localizer::easynav_localizer
 )
+
+find_package(rosgraph_msgs REQUIRED)
+ament_add_gtest(fusion_localizer_clock_wait_tests fusion_localizer_clock_wait_tests.cpp)
+target_link_libraries(fusion_localizer_clock_wait_tests
+  fusion_localizer
+  rclcpp::rclcpp
+  easynav_localizer::easynav_localizer
+  ${rosgraph_msgs_TARGETS}
+)
diff --git a/localizers/easynav_fusion_localizer/tests/fusion_localizer_clock_wait_tests.cpp b/localizers/easynav_fusion_localizer/tests/fusion_localizer_clock_wait_tests.cpp
new file mode 100644
index 00000000..17ccfc2b
--- /dev/null
+++ b/localizers/easynav_fusion_localizer/tests/fusion_localizer_clock_wait_tests.cpp
@@ -0,0 +1,165 @@
+// Copyright 2026 Intelligent Robotics Lab
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+/// \file
+/// \brief With use_sim_time, the filters wait for /clock while configuring, but a shutdown
+/// (a second signal to system_main) stops the wait.
+
+#include <gtest/gtest.h>
+
+#include <atomic>
+#include <chrono>
+#include <cstdarg>
+#include <cstdio>
+#include <future>
+#include <memory>
+#include <string>
+#include <thread>
+#include <vector>
+
+#include "easynav_fusion_localizer/FusionLocalizer.hpp"
+#include "easynav_localizer/LocalizerNode.hpp"
+#include "rclcpp/rclcpp.hpp"
+#include "rcutils/logging.h"
+#include "rosgraph_msgs/msg/clock.hpp"
+
+using namespace std::chrono_literals;
+
+namespace
+{
+
+std::atomic<int> g_clock_warnings{0};
+
+void count_clock_warnings(
+  const rcutils_log_location_t *, int severity, const char *, rcutils_time_point_value_t,
+  const char * format, va_list * args)
+{
+  char msg[512];
+  va_list copy;
+  va_copy(copy, *args);
+  std::vsnprintf(msg, sizeof(msg), format, copy);
+  va_end(copy);
+  if (severity == RCUTILS_LOG_SEVERITY_WARN &&
+    std::string(msg).find("Waiting for the ROS clock to start") != std::string::npos)
+  {
+    ++g_clock_warnings;
+  }
+}
+
+}  // namespace
+
+class FusionClockWaitTest : public ::testing::Test
+{
+protected:
+  void SetUp() override {rclcpp::init(0, nullptr);}
+  void TearDown() override
+  {
+    if (rclcpp::ok()) {rclcpp::shutdown();}
+  }
+
+  // Initializes a local filter in another thread; the node is kept in node_.
+  std::future<void> initialize(bool use_sim_time)
+  {
+    rclcpp::NodeOptions options;
+    options.parameter_overrides(
+    {
+      {"use_sim_time", use_sim_time},
+      {"fusion.local_filter.frequency", 30.0},
+      {"fusion.local_filter.two_d_mode", true},
+      {"fusion.local_filter.publish_tf", false},
+      {"fusion.local_filter.world_frame", "odom"},
+      {"fusion.local_filter.odom0", "clock_wait_odom"},
+    });
+    node_ = std::make_shared<easynav::LocalizerNode>(options);
+    node_->declare_parameter<std::vector<std::string>>(
+      "localizer_types", std::vector<std::string>{});
+    localizer_ = std::make_shared<easynav::FusionLocalizer>();
+    return std::async(
+      std::launch::async, [this]() {localizer_->initialize(node_, "fusion");});
+  }
+
+  std::shared_ptr<easynav::LocalizerNode> node_;
+  std::shared_ptr<easynav::FusionLocalizer> localizer_;
+};
+
+TEST_F(FusionClockWaitTest, WithoutSimTimeItDoesNotWait)
+{
+  auto done = initialize(false);
+  ASSERT_EQ(done.wait_for(5s), std::future_status::ready);
+  EXPECT_NO_THROW(done.get());
+}
+
+TEST_F(FusionClockWaitTest, WithSimTimeItWaitsUntilTheClockStarts)
+{
+  auto done = initialize(true);
+  EXPECT_EQ(done.wait_for(1s), std::future_status::timeout);  // no /clock yet
+
+  auto clock_node = std::make_shared<rclcpp::Node>("clock_wait_publisher");
+  auto pub = clock_node->create_publisher<rosgraph_msgs::msg::Clock>("/clock", 10);
+  rosgraph_msgs::msg::Clock clock;
+  clock.clock.sec = 100;
+  const auto end = std::chrono::steady_clock::now() + 10s;
+  while (done.wait_for(50ms) != std::future_status::ready &&
+    std::chrono::steady_clock::now() < end)
+  {
+    pub->publish(clock);
+  }
+  ASSERT_EQ(done.wait_for(0s), std::future_status::ready);
+  EXPECT_NO_THROW(done.get());
+  EXPECT_EQ(node_->now().seconds(), 100.0);
+}
+
+TEST_F(FusionClockWaitTest, WhileItWaitsItSaysWhy)
+{
+  const auto handler = rcutils_logging_get_output_handler();
+  rcutils_logging_set_output_handler(count_clock_warnings);
+  g_clock_warnings = 0;
+  auto done = initialize(true);
+  EXPECT_EQ(done.wait_for(4s), std::future_status::timeout);
+  EXPECT_EQ(g_clock_warnings, 0);  // every 5 s
+  EXPECT_EQ(done.wait_for(2s), std::future_status::timeout);
+  EXPECT_EQ(g_clock_warnings, 1);
+  rclcpp::shutdown();
+  ASSERT_EQ(done.wait_for(5s), std::future_status::ready);
+  rcutils_logging_set_output_handler(handler);
+  try {
+    done.get();
+  } catch (const std::exception &) {
+  }
+}
+
+TEST_F(FusionClockWaitTest, AShutdownStopsTheWait)
+{
+  auto done = initialize(true);
+  EXPECT_EQ(done.wait_for(1s), std::future_status::timeout);
+  rclcpp::shutdown();
+  // Stops waiting; what is left of the initialization may fail without a context
+  ASSERT_EQ(done.wait_for(5s), std::future_status::ready);
+  try {
+    done.get();
+  } catch (const std::exception &) {
+  }
+}
+
+// Before or while it waits, whichever comes first
+TEST_F(FusionClockWaitTest, AShutdownRightAwayDoesNotHang)
+{
+  auto done = initialize(true);
+  rclcpp::shutdown();
+  ASSERT_EQ(done.wait_for(5s), std::future_status::ready);
+  try {
+    done.get();
+  } catch (const std::exception &) {
+  }
+}