diff --git a/CHANGELOG.md b/CHANGELOG.md
index 87b2e1c..77874e6 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,8 @@ All notable changes to this project are documented here. The format is based on
 
 ## [Unreleased]
 
+## [4.1.0] - 2026-06-07
+
 ### Added
 - Structural mutation helpers on `TreeNode`: `insertChild`, `removeChildAt`, `replaceChild`,
   `moveChild`, `addChildren`, and `sortChildren`.
@@ -89,7 +91,8 @@ A breaking release that cleans up the core API and enforces an explicit public s
 ## [3.1.3]
 - iOS targets and Maven Central (Sonatype Central Portal) publishing.
 
-[Unreleased]: https://github.com/AdrianKuta/Tree-Data-Structure/compare/v4.0.0...HEAD
+[Unreleased]: https://github.com/AdrianKuta/Tree-Data-Structure/compare/v4.1.0...HEAD
+[4.1.0]: https://github.com/AdrianKuta/Tree-Data-Structure/compare/v4.0.0...v4.1.0
 [4.0.0]: https://github.com/AdrianKuta/Tree-Data-Structure/compare/v3.4.0...v4.0.0
 [3.4.0]: https://github.com/AdrianKuta/Tree-Data-Structure/compare/v3.1.5...v3.4.0
 [3.1.5]: https://github.com/AdrianKuta/Tree-Data-Structure/compare/v3.1.3...v3.1.5
diff --git a/README.md b/README.md
index bdbc272..73c2fb5 100644
--- a/README.md
+++ b/README.md
@@ -30,14 +30,14 @@ Gradle (Kotlin DSL):
 ```kotlin
 // commonMain for KMP projects, or any sourceSet/module where you need it
 dependencies {
-    implementation("com.github.adriankuta:tree-structure:4.0.0") // latest version is on the badge above
+    implementation("com.github.adriankuta:tree-structure:4.1.0") // latest version is on the badge above
 }
 ```
 
 Gradle (Groovy):
 ```groovy
 dependencies {
-    implementation "com.github.adriankuta:tree-structure:4.0.0"
+    implementation "com.github.adriankuta:tree-structure:4.1.0"
 }
 ```
 
@@ -46,7 +46,7 @@ Maven:
 <dependency>
   <groupId>com.github.adriankuta</groupId>
   <artifactId>tree-structure</artifactId>
-  <version>4.0.0</version>
+  <version>4.1.0</version>
 </dependency>
 ```
 
@@ -160,7 +160,7 @@ that depends on the core.
 `@Serializable` directly. Convert to and from the acyclic `TreeNodeDto` instead.
 
 ```kotlin
-implementation("com.github.adriankuta:tree-structure-serialization:4.0.0")
+implementation("com.github.adriankuta:tree-structure-serialization:4.1.0")
 ```
 ```kotlin
 val json = Json.encodeToString(root.toDto())
@@ -172,7 +172,7 @@ val restored = Json.decodeFromString<TreeNodeDto<String>>(json).toTreeNode()
 Traverse a tree as a cold `Flow`, which is handy inside coroutine and `ViewModel` pipelines.
 
 ```kotlin
-implementation("com.github.adriankuta:tree-structure-coroutines:4.0.0")
+implementation("com.github.adriankuta:tree-structure-coroutines:4.1.0")
 ```
 ```kotlin
 root.preOrderFlow().collect { println(it.value) }
@@ -185,7 +185,7 @@ A `LazyTree` composable for Compose Multiplatform (JVM/desktop, iOS, Wasm). Only
 are composed, and you decide how each node looks:
 
 ```kotlin
-implementation("com.github.adriankuta:tree-structure-compose:4.0.0")
+implementation("com.github.adriankuta:tree-structure-compose:4.1.0")
 ```
 ```kotlin
 LazyTree(root) { node, depth, expanded, toggle ->
@@ -196,6 +196,23 @@ LazyTree(root) { node, depth, expanded, toggle ->
 }
 ```
 
+### Immutable (`tree-structure-immutable`)
+
+A persistent `ImmutableTreeNode` with structural sharing. Every operation (`addChild`,
+`removeChild`, `mapValues`) returns a **new** root and leaves the original untouched; unchanged
+subtrees are reused, so updates are cheap and old roots stay valid. Backed by
+`kotlinx.collections.immutable`.
+
+```kotlin
+implementation("com.github.adriankuta:tree-structure-immutable:4.1.0")
+```
+```kotlin
+val root = ImmutableTreeNode("World").addChild(ImmutableTreeNode("Europe"))
+val bigger = root.addChild(ImmutableTreeNode("Asia")) // root is unchanged; bigger is a new tree
+
+bigger.preOrder().forEach { println(it.value) } // pre/post/level-order, nodeCount(), height()
+```
+
 ## Notes
 
 `TreeNode` is mutable and not thread-safe. Add your own synchronization if you share a tree across
diff --git a/build.gradle.kts b/build.gradle.kts
index db0806f..18e36ee 100644
--- a/build.gradle.kts
+++ b/build.gradle.kts
@@ -11,7 +11,7 @@ plugins {
 
 val PUBLISH_GROUP_ID = "com.github.adriankuta"
 val PUBLISH_ARTIFACT_ID = "tree-structure"    // base artifact; KMP will add -jvm, -ios*, etc.
-val PUBLISH_VERSION = "4.0.0"
+val PUBLISH_VERSION = "4.1.0"
 
 val snapshot: String? by project