diff --git a/src/frontend/flask_app/templates/base.html b/src/frontend/flask_app/templates/base.html
index 5177d96..abe9db4 100644
--- a/src/frontend/flask_app/templates/base.html
+++ b/src/frontend/flask_app/templates/base.html
@@ -138,7 +138,11 @@
             self.showWarning = false;
           }
         };
-        ['mousemove','mousedown','keypress','touchstart','scroll'].forEach(function(evt) {
+        // 'keydown', not just 'keypress': the numpad calls preventDefault() on every
+        // digit/Enter it reads from the USB caliper, which also suppresses the
+        // keypress that would otherwise follow - an operator working only from the
+        // caliper produced no activity at all and was logged out mid-task (#37.2).
+        ['mousemove','mousedown','keydown','keypress','touchstart','scroll'].forEach(function(evt) {
           window.addEventListener(evt, handler, { passive: true });
         });
       },
diff --git a/src/frontend/flask_app/tests/test_base_inactivity_keydown.py b/src/frontend/flask_app/tests/test_base_inactivity_keydown.py
new file mode 100644
index 0000000..e8e873c
--- /dev/null
+++ b/src/frontend/flask_app/tests/test_base_inactivity_keydown.py
@@ -0,0 +1,27 @@
+"""gitea:Adriano/TieMeasureFlow#37 (point 2).
+
+base.html's auto-logout only counted activity through 'mousemove', 'mousedown',
+'keypress', 'touchstart', 'scroll'. The numpad (static/js/numpad.js) calls
+preventDefault() on every keydown it reads from the USB caliper, which also
+suppresses the keypress that would otherwise follow: an operator working
+purely from the caliper produced no activity at all in the inactivity timer's
+eyes and was logged out mid-task. Adding 'keydown' to the list fixes it -
+keydown always fires regardless of what a later handler does with
+preventDefault().
+"""
+ACTIVITY_EVENTS = "['mousemove','mousedown','keydown','keypress','touchstart','scroll']"
+
+
+def test_inactivity_timer_listens_for_keydown(logged_in_client, mock_api_client, monkeypatch):
+    with logged_in_client.session_transaction() as sess:
+        sess["language"] = "it"
+        sess["auto_logout_minutes"] = 15
+
+    monkeypatch.setattr("blueprints.measure.Config.STATION_CODE", "ST-TEST")
+    mock_api_client.get_station_recipes.return_value = []
+
+    resp = logged_in_client.get("/measure/select")
+    assert resp.status_code == 200
+    html = resp.get_data(as_text=True)
+
+    assert ACTIVITY_EVENTS in html