diff --git a/software/control/laser_engine_widget.py b/software/control/laser_engine_widget.py
index d5ea9e3ac..dff84ee7f 100644
--- a/software/control/laser_engine_widget.py
+++ b/software/control/laser_engine_widget.py
@@ -46,6 +46,20 @@ def _engine_summary_label(status: Optional[SquidLaserEngineStatus], connection_l
     return "Warming up"
 
 
+def _is_engine_measured(module) -> bool:
+    """Whether this engine actually measures the module's temperature.
+
+    Firmware only holds ACTIVE while a channel sits at setpoint: it drops back
+    to WARMING_UP below -0.5 °C and to CHECK_ERROR at or above the +5 °C error
+    threshold. A module reporting ACTIVE far outside that band therefore is not
+    being regulated here — its TEC controller is wired to something else — and
+    its temperature/ΔT columns are floor readings rather than measurements.
+    """
+    if module.state != LaserChannelState.ACTIVE:
+        return True
+    return -0.5 < module.setpoint_diff_c < 5.0
+
+
 def _format_temp(info) -> str:
     return "/".join(f"{m.temperature_c:.1f}" for m in info.modules) + " °C"
 
@@ -116,6 +130,11 @@ def _refresh_channel_lines(self) -> None:
                 continue
             state = info.display_state
             on_off = "ON" if info.laser_ttl_on else "OFF"
+            if not any(_is_engine_measured(m) for m in info.modules):
+                # Showing the floor readings here would look like an ACTIVE
+                # channel sitting far below setpoint. Report the state only.
+                self._channel_lines[key].setText(f"{key:>4}  {on_off:<3}  {state.name:<14}  TEC not engine-controlled")
+                continue
             self._channel_lines[key].setText(
                 f"{key:>4}  {on_off:<3}  {state.name:<14}  {_format_temp(info)}  ΔT {_format_diff(info)}"
             )
diff --git a/software/tests/control/test_laser_engine_widget.py b/software/tests/control/test_laser_engine_widget.py
new file mode 100644
index 000000000..86084c47c
--- /dev/null
+++ b/software/tests/control/test_laser_engine_widget.py
@@ -0,0 +1,45 @@
+"""Unit tests for the Laser Engine tab's display rules."""
+
+from control.laser_engine_widget import _is_engine_measured
+from control.squid_laser_engine import LaserChannelState, TcmModuleInfo
+
+
+def _module(state, setpoint_diff_c, temperature_c=25.0):
+    return TcmModuleInfo(
+        module_index=0,
+        state=state,
+        temperature_c=temperature_c,
+        setpoint_c=temperature_c - setpoint_diff_c,
+        setpoint_diff_c=setpoint_diff_c,
+        tec_voltage=0.0,
+        tec_current=0.0,
+        hi_temp_setpoint_c=30.0,
+    )
+
+
+class TestIsEngineMeasured:
+    def test_active_at_setpoint_is_measured(self):
+        assert _is_engine_measured(_module(LaserChannelState.ACTIVE, 0.0))
+
+    def test_active_within_band_is_measured(self):
+        # Firmware tolerates ACTIVE anywhere in (-0.5, +5.0).
+        assert _is_engine_measured(_module(LaserChannelState.ACTIVE, -0.4))
+        assert _is_engine_measured(_module(LaserChannelState.ACTIVE, 4.9))
+
+    def test_active_far_below_setpoint_is_not_measured(self):
+        # A channel the engine regulates cannot hold ACTIVE here; it would have
+        # dropped to WARMING_UP. So this reading is a floor value, not a
+        # measurement. Matches 638/730 on hardware: 0.4 C with dT -24.6.
+        assert not _is_engine_measured(_module(LaserChannelState.ACTIVE, -24.6, temperature_c=0.4))
+
+    def test_active_at_error_threshold_is_not_measured(self):
+        assert not _is_engine_measured(_module(LaserChannelState.ACTIVE, 5.0))
+
+    def test_warming_up_far_from_setpoint_is_measured(self):
+        # Genuinely warming: far from setpoint is expected and the numbers are
+        # real, so they must still be shown.
+        assert _is_engine_measured(_module(LaserChannelState.WARMING_UP, -66.9, temperature_c=27.2))
+
+    def test_sleep_is_measured(self):
+        # A sleeping channel drifts away from setpoint; still a real reading.
+        assert _is_engine_measured(_module(LaserChannelState.SLEEP, -42.3, temperature_c=51.8))