diff --git a/forgetest/forgetest/suite/setup_burns.py b/forgetest/forgetest/suite/setup_burns.py
index 68dc775..4526183 100644
--- a/forgetest/forgetest/suite/setup_burns.py
+++ b/forgetest/forgetest/suite/setup_burns.py
@@ -81,13 +81,16 @@ def preview_ok(ctx, wid):
 
 
 def emission_ok(ctx, last):
-    """The three witnesses of the burn, from the wizard's result."""
+    """The two witnesses of the burn, from the wizard's result. The head's
+    beam sensor is recorded, never required: the result reports its rise
+    and whether it read as the beam seen."""
     e = (last.get("result") or {}).get("emission") or {}
     ctx.evidence["emission"] = e
     ctx.check(e.get("hv_max", 0) > 30, "the tube current never rose (%s)", e.get("hv_max"))
     ctx.check(e.get("laser_on_samples", 0) > 0, "the kernel never sampled LASER_ON")
-    ctx.check(e.get("thermopile_delta", 0) >= 100, "the thermopile did not see the beam (%s)",
-              e.get("thermopile_delta"))
+    ctx.check(isinstance(e.get("thermopile_delta"), int) and isinstance(e.get("beam_sensor_seen"), bool),
+              "the result does not record the beam sensor: %s", e)
+    ctx.log("the beam sensor rose %s (seen: %s)", e.get("thermopile_delta"), e.get("beam_sensor_seen"))
 
 
 def thickness_answer(ctx):
@@ -219,8 +222,9 @@ def focus_window_ok(ctx, r, before):
                   "head and its tail returns there. With its preview and program served by GET "
                   "/wiz/sheet.svg and /wiz/sheet.gcode and every Z the program commands inside the "
                   "reach /status reports, it burns twelve lines after the press, from the top of "
-                  "the window to the bottom, seen by the three witnesses (the tube current, the "
-                  "kernel's LASER_ON samples, the thermopile rise). The pick is line 11. The "
+                  "the window to the bottom, seen by the two witnesses (the tube current and the "
+                  "kernel's LASER_ON samples), with the beam sensor's rise recorded and not "
+                  "required. The pick is line 11. The "
                   "result carries its keys; the ladder ran in the window the machine held, which "
                   "the burn leaves as found (it writes the edge alone, the one its result "
                   "reports); every ladder height lies in the reach; the program served afterward "
@@ -273,7 +277,7 @@ def focus(ctx):
                   "its preview and program served and every Z the program commands inside the "
                   "reach /status reports, it burns twelve rungs from 2 to 24 percent density at "
                   "the focal point on the scrap's surface, the floor and the curve off for the "
-                  "job, after the press, seen by the three witnesses. The pick is 8, so the floor "
+                  "job, after the press, seen by the two witnesses. The pick is 8, so the floor "
                   "written is 10 (two above it) and the setting reads it; the result carries its "
                   "keys; the record carries laser.floor at version 1. laser_floor_density is "
                   "restored at the end.")
diff --git a/forgetest/tests/test_setup_burns.py b/forgetest/tests/test_setup_burns.py
index fe906b1..34cfc77 100644
--- a/forgetest/tests/test_setup_burns.py
+++ b/forgetest/tests/test_setup_burns.py
@@ -22,7 +22,8 @@ from forgetest.runner import Context, Failed, Run  # noqa: E402
 from forgetest.suite import setup_burns, setup_dark  # noqa: E402
 
 LIVE = ["laser.focus", "laser.floor"]
-EMISSION = {"hv_max": 610, "laser_on_samples": 900, "thermopile_delta": 600, "lit_s": 30.0}
+EMISSION = {"hv_max": 610, "laser_on_samples": 900, "thermopile_delta": 600, "beam_sensor_seen": True,
+            "lit_s": 30.0}
 SPM = 2.922                     # the lens screw, half-steps per mm ($102)
 EDGE_DEFAULT = 3.35             # the edge's height while the setting is unset (lens.h)
 
@@ -368,6 +369,21 @@ class BurnRunTests(unittest.TestCase):
         self.assertIn("the tube current never rose", str(cm.exception))
         self.assert_found()
 
+    def test_a_burn_with_a_silent_beam_sensor_passes(self):
+        # A head whose beam sensor gives no output: the tube current and
+        # LASER_ON saw the beam, so the burn counts.
+        self.daemon.patch["laser.floor"] = {"emission": dict(EMISSION, thermopile_delta=0,
+                                                             beam_sensor_seen=False)}
+        self.run_test("setup.floor")
+        self.assert_found()
+
+    def test_a_burn_that_does_not_record_the_beam_sensor_fails(self):
+        self.daemon.patch["laser.floor"] = {"emission": {"hv_max": 610, "laser_on_samples": 900}}
+        with self.assertRaises(Failed) as cm:
+            self.run_test("setup.floor")
+        self.assertIn("the result does not record the beam sensor", str(cm.exception))
+        self.assert_found()
+
     def test_a_focus_burn_that_writes_the_window_fails(self):
         # The focus burn writes the edge alone: the window is the Lens
         # travel check's. A burn that moves it fails, and it goes back.