From c329bb4000fb9a7ef8873eee3eb6ee86b98facaa Mon Sep 17 00:00:00 2001
From: Erik Montnemery <erik@montnemery.com>
Date: Wed, 3 Jun 2026 19:58:32 +0200
Subject: [PATCH] Don't log configuration errors when executing WS
 subscribe_trigger (#172918)

---
 .../components/websocket_api/commands.py      | 19 +++-
 .../components/websocket_api/test_commands.py | 97 +++++++++++++++++++
 2 files changed, 115 insertions(+), 1 deletion(-)

diff --git a/homeassistant/components/websocket_api/commands.py b/homeassistant/components/websocket_api/commands.py
index 68a52fca9ab6..5ca6cd6ddce3 100644
--- a/homeassistant/components/websocket_api/commands.py
+++ b/homeassistant/components/websocket_api/commands.py
@@ -980,7 +980,24 @@ async def handle_subscribe_trigger(
     hass: HomeAssistant, connection: ActiveConnection, msg: dict[str, Any]
 ) -> None:
     """Handle subscribe trigger command."""
-    trigger_config = await async_validate_trigger_config(hass, msg["trigger"])
+    # Validating the trigger config can fail on bad user input. Handle those
+    # errors here so they are reported to the client without being logged as
+    # unexpected errors by the default websocket error handler.
+    try:
+        trigger_config = await async_validate_trigger_config(hass, msg["trigger"])
+    except vol.Invalid as err:
+        connection.send_error(msg["id"], const.ERR_INVALID_FORMAT, str(err))
+        return
+    except HomeAssistantError as err:
+        connection.send_error(
+            msg["id"],
+            const.ERR_HOME_ASSISTANT_ERROR,
+            str(err),
+            translation_domain=err.translation_domain,
+            translation_key=err.translation_key,
+            translation_placeholders=err.translation_placeholders,
+        )
+        return
 
     @callback
     def forward_triggers(
diff --git a/tests/components/websocket_api/test_commands.py b/tests/components/websocket_api/test_commands.py
index 71771e355bdf..b987ce14dd72 100644
--- a/tests/components/websocket_api/test_commands.py
+++ b/tests/components/websocket_api/test_commands.py
@@ -2745,6 +2745,103 @@ async def test_subscribe_trigger(
     assert sum(hass.bus.async_listeners().values()) == init_count
 
 
+@pytest.mark.parametrize(
+    ("trigger", "expected_error"),
+    [
+        # Unknown trigger platform
+        (
+            {"platform": "nonexistent"},
+            {
+                "code": "invalid_format",
+                "message": "Invalid trigger 'nonexistent' specified",
+            },
+        ),
+        # Missing mandatory config for the trigger platform
+        (
+            {"platform": "numeric_state"},
+            {
+                "code": "invalid_format",
+                "message": "required key not provided @ data['entity_id']",
+            },
+        ),
+        # Unknown device, raised as a HomeAssistantError by the platform validator
+        (
+            {"platform": "device", "domain": "light", "device_id": "nonexistent"},
+            {
+                "code": "home_assistant_error",
+                "message": "Unknown device 'nonexistent'",
+            },
+        ),
+    ],
+)
+async def test_subscribe_trigger_config_error(
+    hass: HomeAssistant,
+    websocket_client: MockHAClientWebSocket,
+    caplog: pytest.LogCaptureFixture,
+    trigger: dict,
+    expected_error: dict,
+) -> None:
+    """Test trigger config errors are reported to the client without logging."""
+    caplog.set_level(logging.ERROR)
+
+    await websocket_client.send_json_auto_id(
+        {"type": "subscribe_trigger", "trigger": trigger}
+    )
+
+    msg = await websocket_client.receive_json()
+    assert msg["type"] == const.TYPE_RESULT
+    assert not msg["success"]
+    assert msg["error"] == expected_error
+
+    # The expected error is not logged by the default websocket error handler
+    assert "Error handling message" not in caplog.text
+
+
+async def test_subscribe_trigger_template_error_spams_log(
+    hass: HomeAssistant,
+    websocket_client: MockHAClientWebSocket,
+    caplog: pytest.LogCaptureFixture,
+) -> None:
+    """Test that a failing trigger template spams the log.
+
+    This documents unwanted behavior. Unlike subscribe_condition and
+    test_condition, subscribe_trigger does not suppress repeated template
+    variable errors: a trigger is evaluated event-driven by its platform (here
+    via async_track_template_result), outside any trace context, so the
+    trace-based suppression used for conditions does not apply. This should be
+    fixed in the future so the error is suppressed/forwarded instead of being
+    logged on every re-render.
+    """
+    caplog.set_level(logging.WARNING)
+    hass.states.async_set("sensor.test", "1")
+
+    await websocket_client.send_json_auto_id(
+        {
+            "type": "subscribe_trigger",
+            "trigger": {
+                "platform": "template",
+                "value_template": "{{ states('sensor.test') }}{{ undefined_variable }}",
+            },
+        }
+    )
+
+    msg = await websocket_client.receive_json()
+    assert msg["type"] == const.TYPE_RESULT
+    assert msg["success"]
+
+    # Each re-render of the template logs the undefined variable error again
+    for state in ("2", "3", "4"):
+        hass.states.async_set("sensor.test", state)
+        await hass.async_block_till_done()
+
+    assert (
+        caplog.text.count(
+            "Template variable warning: 'undefined_variable' is undefined"
+        )
+        > 1
+    )
+
+
 async def test_test_condition(
     hass: HomeAssistant, websocket_client: MockHAClientWebSocket
 ) -> None: