Loadpoint: keep vehicle SoC when re-assigning the same default vehicle

core/loadpoint_vehicle.go

@@ -162,7 +162,14 @@ func (lp *Loadpoint) setActiveVehicle(v api.Vehicle) {
 
 	// re-publish vehicle settings
 	lp.publish(keys.PhasesActive, lp.ActivePhases())
-	lp.unpublishVehicle()
+
+	// only reset published vehicle data when the active vehicle actually changed.
+	// vehicleDefaultOrDetect re-assigns the same default vehicle on every reconnect
+	// to refresh the soc estimator (#27359); zeroing a still-valid soc there makes
+	// vehicleSoc/vehicleRange flap to 0 while charging until the next soc read.
+	if from != to {
+		lp.unpublishVehicle()
+	}
 
 	// publish effective values
 	lp.PublishEffectiveValues()

core/loadpoint_vehicle_test.go

@@ -323,6 +323,44 @@ func TestDefaultVehicle(t *testing.T) {
 	assert.Nil(t, lp.vehicle, "expected no vehicle")
 }
 
+// TestReassignActiveVehicleKeepsSoc is a regression test for vehicleSoc dropping to
+// 0 while charging. vehicleDefaultOrDetect re-assigns the already-active default
+// vehicle on every (re)connect so the soc estimator is refreshed for the new session
+// (#27359, #27364). setActiveVehicle unconditionally calls unpublishVehicle, which
+// zeroes vehicleSoc and publishes 0. When the active vehicle does not actually
+// change, a known soc must be preserved - otherwise /api/state and messaging show 0
+// until the next successful soc read, which manifests as the soc flapping to 0 while
+// charging after an evcc restart mid-session.
+func TestReassignActiveVehicleKeepsSoc(t *testing.T) {
+	ctrl := gomock.NewController(t)
+
+	v := api.NewMockVehicle(ctrl)
+	v.EXPECT().GetTitle().Return("default").AnyTimes()
+	v.EXPECT().Icon().Return("").AnyTimes()
+	v.EXPECT().Capacity().AnyTimes()
+	v.EXPECT().Phases().AnyTimes()
+	v.EXPECT().OnIdentified().Return(api.ActionConfig{}).AnyTimes()
+
+	lp := NewLoadpoint(util.NewLogger("foo"), settings.NewDatabaseSettingsAdapter("foo"))
+	lp.defaultVehicle = v
+
+	x, y, z := createChannels(t)
+	attachChannels(lp, x, y, z)
+
+	// vehicle becomes active and a soc has been read and published
+	lp.setActiveVehicle(v)
+	lp.vehicleSoc = 71
+
+	// same default vehicle re-assigned (e.g. vehicleDefaultOrDetect on reconnect)
+	lp.setActiveVehicle(v)
+	assert.Equal(t, v, lp.vehicle, "expected same vehicle to stay active")
+	assert.Equal(t, 71.0, lp.vehicleSoc, "soc must be preserved when the active vehicle is unchanged")
+
+	// switching the active vehicle must still clear the stale soc
+	lp.setActiveVehicle(nil)
+	assert.Zero(t, lp.vehicleSoc, "soc must be cleared when the vehicle changes")
+}
+
 // integratedDeviceCharger is a minimal charger advertising the IntegratedDevice feature.
 type integratedDeviceCharger struct{}