fix: Propagate Namespace correctly to Helm

api/internal/target/kusttarget.go

@@ -127,11 +127,11 @@ func (kt *KustTarget) MakeCustomizedResMap() (resmap.ResMap, error) {
 }
 
 func (kt *KustTarget) makeCustomizedResMap() (resmap.ResMap, error) {
-	var origin *resource.Origin
-	if len(kt.kustomization.BuildMetadata) != 0 {
-		origin = &resource.Origin{}
-	}
-	kt.origin = origin
+	// Track origin for all resources so builtins can make decisions
+	// based on where resources originated from.
+	// Origin annotations will be stripped from the output if not
+	// requested via build metadata options.
+	kt.origin = &resource.Origin{}
 	ra, err := kt.AccumulateTarget()
 	if err != nil {
 		return nil, err
@@ -496,6 +496,11 @@ func (kt *KustTarget) accumulateDirectory(
 	}
 	subKt.kustomization.BuildMetadata = kt.kustomization.BuildMetadata
 	subKt.origin = kt.origin
+	// Propagate namespace to child kustomization if child doesn't have one
+	// This ensures Helm charts in base kustomizations inherit namespace from overlays
+	if subKt.kustomization.Namespace == "" && kt.kustomization.Namespace != "" {
+		subKt.kustomization.Namespace = kt.kustomization.Namespace
+	}
 	var bytes []byte
 	if openApiPath, exists := subKt.Kustomization().OpenAPI["path"]; exists {
 		bytes, err = ldr.Load(openApiPath)

api/internal/target/kusttarget_configplugin.go

@@ -166,6 +166,11 @@ var generatorConfigurators = map[builtinhelpers.BuiltinPluginType]func(
 		for _, chart := range kt.kustomization.HelmCharts {
 			c.HelmGlobals = globals
 			c.HelmChart = chart
+			// Pass kustomize namespace to helm
+			// Fixes https://github.com/kubernetes-sigs/kustomize/issues/5566
+			if c.HelmChart.Namespace == "" && kt.kustomization.Namespace != "" {
+				c.HelmChart.Namespace = kt.kustomization.Namespace
+			}
 			p := f()
 			if err = kt.configureBuiltinPlugin(p, c, bpt); err != nil {
 				return nil, err

api/internal/target/kusttarget_test.go

@@ -300,6 +300,8 @@ metadata:
 		require.NoError(t, expected.Append(r), "failed to append resource: %v")
 	}
 	expected.RemoveBuildAnnotations()
+	require.NoError(t, expected.RemoveTransformerAnnotations())
+	require.NoError(t, expected.RemoveOriginAnnotations())
 	expYaml, err := expected.AsYaml()
 	require.NoError(t, err)
 
@@ -308,6 +310,8 @@ metadata:
 	actual, err := kt.MakeCustomizedResMap()
 	require.NoError(t, err)
 	actual.RemoveBuildAnnotations()
+	require.NoError(t, actual.RemoveTransformerAnnotations())
+	require.NoError(t, actual.RemoveOriginAnnotations())
 	actYaml, err := actual.AsYaml()
 	require.NoError(t, err)
 	assert.Equal(t, string(expYaml), string(actYaml))
@@ -411,6 +415,8 @@ metadata:
 		require.NoError(t, err)
 	}
 	expected.RemoveBuildAnnotations()
+	require.NoError(t, expected.RemoveTransformerAnnotations())
+	require.NoError(t, expected.RemoveOriginAnnotations())
 	expYaml, err := expected.AsYaml()
 	require.NoError(t, err)
 
@@ -419,6 +425,8 @@ metadata:
 	actual, err := kt.MakeCustomizedResMap()
 	require.NoError(t, err)
 	actual.RemoveBuildAnnotations()
+	require.NoError(t, actual.RemoveTransformerAnnotations())
+	require.NoError(t, actual.RemoveOriginAnnotations())
 	actYaml, err := actual.AsYaml()
 	require.NoError(t, err)
 	require.Equal(t, string(expYaml), string(actYaml))