From 4e75138d2424f4935d3f9b1a9b332646630650bb Mon Sep 17 00:00:00 2001
From: koba1t <kobdotsh@gmail.com>
Date: Tue, 13 Jan 2026 08:09:14 +0900
Subject: [PATCH] fix: apply namespace propagation for helmCharts only

---
 api/internal/target/kusttarget.go             | 26 ++++++++++++-------
 .../target/kusttarget_configplugin.go         |  9 +++++--
 api/krusty/namespacepropagation_test.go       |  1 -
 3 files changed, 23 insertions(+), 13 deletions(-)

diff --git a/api/internal/target/kusttarget.go b/api/internal/target/kusttarget.go
index 3eb4c00c0..8176ba9eb 100644
--- a/api/internal/target/kusttarget.go
+++ b/api/internal/target/kusttarget.go
@@ -29,13 +29,14 @@ import (
 
 // KustTarget encapsulates the entirety of a kustomization build.
 type KustTarget struct {
-	kustomization *types.Kustomization
-	kustFileName  string
-	ldr           ifc.Loader
-	validator     ifc.Validator
-	rFactory      *resmap.Factory
-	pLdr          *loader.Loader
-	origin        *resource.Origin
+	kustomization   *types.Kustomization
+	kustFileName    string
+	ldr             ifc.Loader
+	validator       ifc.Validator
+	rFactory        *resmap.Factory
+	pLdr            *loader.Loader
+	origin          *resource.Origin
+	parentNamespace string // namespace inherited from parent kustomization for HelmCharts
 }
 
 // NewKustTarget returns a new instance of KustTarget.
@@ -496,10 +497,15 @@ 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
+	// Propagate namespace to child kustomization's parentNamespace for HelmCharts
 	// This ensures Helm charts in base kustomizations inherit namespace from overlays
-	if subKt.kustomization.Namespace == "" && kt.kustomization.Namespace != "" {
-		subKt.kustomization.Namespace = kt.kustomization.Namespace
+	// without affecting other transformers like patches
+	// Fixes https://github.com/kubernetes-sigs/kustomize/issues/6031
+	// Fixes https://github.com/kubernetes-sigs/kustomize/issues/6027
+	if kt.kustomization.Namespace != "" {
+		subKt.parentNamespace = kt.kustomization.Namespace
+	} else if kt.parentNamespace != "" {
+		subKt.parentNamespace = kt.parentNamespace
 	}
 	var bytes []byte
 	if openApiPath, exists := subKt.Kustomization().OpenAPI["path"]; exists {
diff --git a/api/internal/target/kusttarget_configplugin.go b/api/internal/target/kusttarget_configplugin.go
index c41d6c84f..bd358b484 100644
--- a/api/internal/target/kusttarget_configplugin.go
+++ b/api/internal/target/kusttarget_configplugin.go
@@ -168,8 +168,13 @@ var generatorConfigurators = map[builtinhelpers.BuiltinPluginType]func(
 			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
+			// Also propagate parent namespace for multi-level kustomization hierarchies
+			if c.HelmChart.Namespace == "" {
+				if kt.kustomization.Namespace != "" {
+					c.HelmChart.Namespace = kt.kustomization.Namespace
+				} else if kt.parentNamespace != "" {
+					c.HelmChart.Namespace = kt.parentNamespace
+				}
 			}
 			p := f()
 			if err = kt.configureBuiltinPlugin(p, c, bpt); err != nil {
diff --git a/api/krusty/namespacepropagation_test.go b/api/krusty/namespacepropagation_test.go
index 152c2b967..d785f5439 100644
--- a/api/krusty/namespacepropagation_test.go
+++ b/api/krusty/namespacepropagation_test.go
@@ -149,7 +149,6 @@ OVERLAY_ENV=overlay
 apiVersion: v1
 data:
   BASE_LAYER_ENV: base
-  COMMON_ENV: common
   OVERLAY_ENV: overlay
 kind: ConfigMap
 metadata: