diff --git a/.github/workflows/publishRelease.yml b/.github/workflows/publishRelease.yml
index 68b2dbe..4e36419 100644
--- a/.github/workflows/publishRelease.yml
+++ b/.github/workflows/publishRelease.yml
@@ -16,7 +16,10 @@ jobs:
     needs: test
     name: Publish Production
     environment: production
-    runs-on: ubuntu-latest
+    # MUST be macOS: Kotlin/Native Apple targets (iosArm64/iosX64/iosSimulatorArm64) can only be
+    # built on a macOS host. On a Linux runner those tasks are silently skipped, so the iOS klibs
+    # never get uploaded (the build still goes green) — exactly what happened for 3.1.5–4.1.0.
+    runs-on: macos-latest
     steps:
       - name: Check out code
         uses: actions/checkout@v4
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 77874e6..09bc313 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,14 @@ All notable changes to this project are documented here. The format is based on
 
 ## [Unreleased]
 
+## [4.1.1] - 2026-06-08
+
+### Fixed
+- Restored the Apple/iOS artifacts (`iosArm64`, `iosX64`, `iosSimulatorArm64`) for the core and every
+  module. The release workflow published from a Linux runner, which cannot build Kotlin/Native Apple
+  targets, so they were silently omitted from 3.1.5–4.1.0; publishing now runs on macOS. No API or
+  behavior changes from 4.1.0 — this is a packaging fix only.
+
 ## [4.1.0] - 2026-06-07
 
 ### Added
@@ -91,7 +99,8 @@ 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/v4.1.0...HEAD
+[Unreleased]: https://github.com/AdrianKuta/Tree-Data-Structure/compare/v4.1.1...HEAD
+[4.1.1]: https://github.com/AdrianKuta/Tree-Data-Structure/compare/v4.1.0...v4.1.1
 [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
diff --git a/README.md b/README.md
index 73c2fb5..1ec1c2a 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:4.1.0") // latest version is on the badge above
+    implementation("com.github.adriankuta:tree-structure:4.1.1") // latest version is on the badge above
 }
 ```
 
 Gradle (Groovy):
 ```groovy
 dependencies {
-    implementation "com.github.adriankuta:tree-structure:4.1.0"
+    implementation "com.github.adriankuta:tree-structure:4.1.1"
 }
 ```
 
@@ -46,7 +46,7 @@ Maven:
 <dependency>
   <groupId>com.github.adriankuta</groupId>
   <artifactId>tree-structure</artifactId>
-  <version>4.1.0</version>
+  <version>4.1.1</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:4.1.0")
+implementation("com.github.adriankuta:tree-structure-serialization:4.1.1")
 ```
 ```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:4.1.0")
+implementation("com.github.adriankuta:tree-structure-coroutines:4.1.1")
 ```
 ```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:4.1.0")
+implementation("com.github.adriankuta:tree-structure-compose:4.1.1")
 ```
 ```kotlin
 LazyTree(root) { node, depth, expanded, toggle ->
@@ -204,7 +204,7 @@ 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")
+implementation("com.github.adriankuta:tree-structure-immutable:4.1.1")
 ```
 ```kotlin
 val root = ImmutableTreeNode("World").addChild(ImmutableTreeNode("Europe"))
diff --git a/build.gradle.kts b/build.gradle.kts
index 18e36ee..244b730 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 = "4.1.0"
+val PUBLISH_VERSION = "4.1.1"
 
 val snapshot: String? by project
 
diff --git a/docs/superpowers/specs/2026-06-07-tree-enhancements-design.md b/docs/superpowers/specs/2026-06-07-tree-enhancements-design.md
new file mode 100644
index 0000000..d327d4a
--- /dev/null
+++ b/docs/superpowers/specs/2026-06-07-tree-enhancements-design.md
@@ -0,0 +1,77 @@
+# Design — four additive enhancements to `tree-structure` (target 4.1.0)
+
+Date: 2026-06-07. Source issues: #34, #35, #36, #33. Integration: **four separate PRs**,
+one per issue (`Closes #NN`), matching the repo's per-issue PR convention (#32).
+
+## Shared rules (every issue)
+
+- `explicitApi()` is on everywhere → every new public declaration is `public` with KDoc.
+- New tests live in `commonTest`, use `kotlin("test")`, and mirror the existing test style
+  (`TreeNodeV4Test.kt`, `TreeNodeNavigationTest.kt`, …).
+- Add a bullet to `CHANGELOG.md` under `## [Unreleased]` → `### Added` (do **not** bump
+  `PUBLISH_VERSION`; releases are a separate manual step).
+- Regenerate the binary-compatibility baseline with `./gradlew apiDump`; verify with `apiCheck`.
+- Do not modify the core public surface in a breaking way — these are additive only.
+
+## #34 — Structural mutation helpers → **members on `TreeNode`**
+
+Members (not extensions) because they need the private `_children`/`_parent` and the cycle/parent
+validation.
+
+- Extract the existing inline validation from `addChild` into a private
+  `validateAttachable(child)` and reuse it.
+- `insertChild(index: Int, child)` — validated insert at index (bounds `0.._children.size`).
+- `removeChildAt(index: Int): TreeNode<T>` — remove and return the detached child.
+- `replaceChild(index: Int, child): TreeNode<T>` — swap, return the old (now detached) child.
+- `moveChild(child, toIndex): Boolean` — reorder an existing direct child; no re-parent/cycle
+  check needed (it is already a child); `false` if `child` is not a direct child.
+- `addChildren(vararg children)` — validated append of several (per-child `addChild` semantics).
+- `sortChildren(comparator: Comparator<TreeNode<T>>)` — stable in-place reorder.
+
+## #35 — Query algorithms → **extensions** in new `TreeNodeQueryExt.kt`
+
+Built on the public API (`ancestors()`, `parent`, `depth()`, sequences). Return `null` when the
+two nodes are unrelated (different trees).
+
+- `lowestCommonAncestor(other): TreeNode<T>?` — deepest common node; includes self/other as
+  candidates (`LCA(a, a) == a`, `LCA(a, descendantOfA) == a`).
+- `distance(other): Int?` — `depth(this) + depth(other) - 2 * depth(lca)`.
+- `pathBetween(other): List<TreeNode<T>>?` — `[this … lca … other]`.
+- `contains(value): Boolean` — value search over the subtree, including the receiver.
+
+Document complexity (parent-walk based; O(depth) for LCA/distance, O(n) for `contains`).
+
+## #36 — Customizable `prettyString()` → **extension** in new `TreeNodePrettyPrintExt.kt`
+
+- `data class TreeConnectors(branch, lastBranch, vertical, empty)` with a `companion`:
+  `Default` (current Unicode box-drawing) and `Ascii`.
+- `fun TreeNode<T>.prettyString(connectors = TreeConnectors.Default,
+  render: (value: T, depth: Int, isLast: Boolean) -> String = { v, _, _ -> v.toString() }): String`.
+- The no-arg member `prettyString()` is unchanged; member resolution wins for `node.prettyString()`,
+  so existing behaviour and output are byte-for-byte identical.
+
+## #33 — Immutable variant → **new module `:tree-structure-immutable`**
+
+Largest item; fully isolated from the other three except for `settings.gradle.kts`,
+`libs.versions.toml`, the root `build.gradle.kts` Dokka aggregation block, and `CHANGELOG.md`.
+
+- `settings.gradle.kts`: `include(":tree-structure-immutable")`.
+- New `build.gradle.kts` mirroring the serialization module's KMP target matrix; deps
+  `api(project(":"))` + `kotlinx-collections-immutable`.
+- `libs.versions.toml`: add `kotlinx-collections-immutable` (a recent stable, e.g. 0.3.8) and
+  wire it.
+- Root `build.gradle.kts`: add `dokka(project(":tree-structure-immutable"))` to the aggregation.
+- `ImmutableTreeNode<T>` backed by `persistentListOf` children; `addChild` / `removeChild` /
+  `mapValues` return a new root with unchanged subtrees structurally shared. Mirror pre/post/
+  level-order traversal helpers.
+- Its own `tree-structure-immutable/api/` baseline via `apiDump`.
+
+## Orchestration
+
+- Four git worktrees off `origin/master`, one branch each (`feat/...`), for full isolation — no
+  collisions on `TreeNode.kt`, `api/*.api`, or `CHANGELOG.md`.
+- A workflow pipelines each issue: implement (code + KDoc + tests + CHANGELOG + `apiDump`) and
+  verify locally (`jvmTest` + `apiCheck`), then an adversarial reviewer checks issue-conformance,
+  test quality, invariants, explicit API, `.api` freshness, and that it builds. Local checks are
+  JVM-only for speed; CI validates the full KMP matrix on each PR.
+- Then push each passing branch and open a PR (`Closes #NN`); remove the worktrees afterward.