diff --git a/API-CHANGES.md b/API-CHANGES.md
index 211d0c3..9faa90a 100644
--- a/API-CHANGES.md
+++ b/API-CHANGES.md
@@ -7,6 +7,28 @@ _Note_: API changes are expected to reduce significantly after the `1.x`
 release. In most cases, an alternative will be provided to ensure relatively
 smooth transition to the new APIs.
 
+## Release 2.2.0 Changes
+
+* [Tree::TreeNode#add][add] now raises `ArgumentError` when attempting to add
+  an ancestor node as a child, preventing cycles.
+
+* [Tree::TreeNode#remove_all!][remove_all] now detaches children by clearing
+  their parent links.
+
+* [Tree::TreeNode#rename_child][rename_child] now raises `ArgumentError` if the
+  new name collides with an existing sibling.
+
+* [Tree::BinaryTreeNode#set_child_at][set_child_at] now raises `ArgumentError`
+  for invalid indices and cleans up parent/hash references when replacing or
+  clearing a child.
+
+* [Tree::TreeNode#postordered_each][postordered_each] and
+  [Tree::TreeNode#breadth_each][breadth_each] now skip `nil` children to
+  support binary trees with missing children.
+
+* [Tree::TreeNode#each_level][each_level] now returns a level-wise enumerator
+  when called without a block.
+
 ## Release 2.1.0 Changes
 
 * Minimum Ruby version has been bumped to 2.7 and above
@@ -143,6 +165,7 @@ smooth transition to the new APIs.
 [detached_subtree_copy]: rdoc-ref:Tree::TreeNode#detached_subtree_copy
 [dup]: rdoc-ref:Tree::TreeNode#dup
 [each]: rdoc-ref:Tree::TreeNode#each
+[each_level]: rdoc-ref:Tree::TreeNode#each_level
 [in_degree]: rdoc-ref:Tree::Utils::TreeMetricsHandler#in_degree
 [initialize]: rdoc-ref:Tree::TreeNode#initialize
 [inordered_each]: rdoc-ref:Tree::BinaryTreeNode#inordered_each
@@ -155,5 +178,8 @@ smooth transition to the new APIs.
 [postordered_each]: rdoc-ref:Tree::TreeNode#postordered_each
 [preordered_each]: rdoc-ref:Tree::TreeNode#preordered_each
 [previous_sibling]: rdoc-ref:Tree::TreeNode#previous_sibling
+[remove_all]: rdoc-ref:Tree::TreeNode#remove_all!
+[rename_child]: rdoc-ref:Tree::TreeNode#rename_child
+[set_child_at]: rdoc-ref:Tree::BinaryTreeNode#set_child_at
 [siblings]: rdoc-ref:Tree::TreeNode#siblings
 [to_json]: rdoc-ref:Tree::Utils::JSONConverter#to_json
diff --git a/Gemfile.lock b/Gemfile.lock
index 6974d45..3e3155f 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -1,7 +1,7 @@
 PATH
   remote: .
   specs:
-    rubytree (2.1.1)
+    rubytree (2.2.0)
       json (~> 2.0, > 2.9)
 
 GEM
diff --git a/History.md b/History.md
index 37a146c..1d571ac 100644
--- a/History.md
+++ b/History.md
@@ -1,5 +1,23 @@
 # History of Changes
 
+### 2.2.0 / 2026-02-06
+
+* Prevent cycles by rejecting attempts to add an ancestor as a child.
+
+* Ensure `remove_all!` detaches children by clearing their parent links.
+
+* Raise on sibling name collisions in `rename_child`.
+
+* Harden binary tree child assignment (`set_child_at`) with proper index errors
+  and cleanup of parent/hash references.
+
+* Make traversals resilient to missing children by skipping `nil` nodes in
+  `postordered_each` and `breadth_each`.
+
+* Return a level-wise enumerator from `each_level` when no block is given.
+
+* Improve `to_s` formatting to show `<Empty>` for nil content.
+
 ### 2.1.1 / 2024-12-19
 
 * 2.1.1 is a minor update that updates all dependencies and updates the guard
diff --git a/Rakefile b/Rakefile
index c56e6ab..717c92e 100644
--- a/Rakefile
+++ b/Rakefile
@@ -2,7 +2,7 @@
 #
 # Rakefile - This file is part of the RubyTree package.
 #
-# Copyright (c) 2006-2022  Anupam Sengupta
+# Copyright (c) 2006-2024  Anupam Sengupta
 #
 # All rights reserved.
 #
@@ -160,9 +160,16 @@ namespace :gem do
     pkg.need_tar = true
   end
 
-  desc 'Push the gem into the Rubygems repository'
+  desc 'Push the gem into the Rubygems and Github repositories'
   task push: :gem do
+    github_repo = 'https://rubygems.pkg.github.com/evolve75'
+
+    # This pushes to the standard RubyGems registry
     sh "gem push pkg/#{GEM_NAME}"
+
+    # For github, the credentials key is assumed to be github
+    # See: https://docs.github.com/en/packages/working-with-a-github-packages-registry/
+    sh "gem push --key github --host #{github_repo} pkg/#{GEM_NAME}"
   end
 end
 
diff --git a/lib/tree.rb b/lib/tree.rb
index ef23fe1..b169583 100644
--- a/lib/tree.rb
+++ b/lib/tree.rb
@@ -318,7 +318,8 @@ def marshal_load(dumped_tree_array)
     #
     # @return [String] A string representation of the node.
     def to_s
-      "Node Name: #{@name} Content: #{@content.to_s || '<Empty>'} " \
+      content_str = @content.nil? ? '<Empty>' : @content.to_s
+      "Node Name: #{@name} Content: #{content_str} " \
         "Parent: #{root? ? '<None>' : @parent.name.to_s} "       \
         "Children: #{@children.length} Total Nodes: #{size}"
     end
@@ -394,6 +395,10 @@ def add(child, at_index = -1)
 
       raise ArgumentError, 'Attempting add root as a child' if child.equal?(root)
 
+      if (ancestors = parentage) && ancestors.include?(child)
+        raise ArgumentError, 'Attempting add ancestor as a child'
+      end
+
       # Lazy man's unique test, won't test if children of child are unique in
       # this tree too.
       raise "Child #{child.name} already added!"\
@@ -453,6 +458,9 @@ def rename_child(old_name, new_name)
       raise ArgumentError, "Invalid child name specified: #{old_name}"\
             unless @children_hash.key?(old_name)
 
+      raise ArgumentError, "Child name already exists: #{new_name}"\
+            if @children_hash.key?(new_name)
+
       @children_hash[new_name] = @children_hash.delete(old_name)
       @children_hash[new_name].name = new_name
     end
@@ -539,7 +547,10 @@ def remove_from_parent!
     # @see #remove!
     # @see #remove_from_parent!
     def remove_all!
-      @children.each(&:remove_all!)
+      @children.each do |child|
+        child.remove_all!
+        child.set_as_root!
+      end
 
       @children_hash.clear
       @children.clear
@@ -669,7 +680,7 @@ def postordered_each
           peek_node.visited = true
           # Add the children to the stack. Use the marking structure.
           marked_children =
-            peek_node.node.children.map { |node| marked_node.new(node, false) }
+            peek_node.node.children.compact.map { |node| marked_node.new(node, false) }
           node_stack = marked_children.concat(node_stack)
           next
         else
@@ -700,9 +711,11 @@ def breadth_each
       # Use a queue to do breadth traversal
       until node_queue.empty?
         node_to_traverse = node_queue.shift
+        next unless node_to_traverse
+
         yield node_to_traverse
         # Enqueue the children from left to right.
-        node_to_traverse.children { |child| node_queue.push child }
+        node_to_traverse.children { |child| node_queue.push child if child }
       end
 
       self if block_given?
@@ -770,7 +783,7 @@ def each_level
         end
         self
       else
-        each
+        to_enum(:each_level)
       end
     end
 
diff --git a/lib/tree/binarytree.rb b/lib/tree/binarytree.rb
index 15f3589..8f773eb 100644
--- a/lib/tree/binarytree.rb
+++ b/lib/tree/binarytree.rb
@@ -203,12 +203,29 @@ def inordered_each
     #
     # @raise [ArgumentError] If the index is out of limits.
     def set_child_at(child, at_index)
-      raise ArgumentError 'A binary tree cannot have more than two children.'\
-                          unless (0..1).include? at_index
+      raise ArgumentError, 'A binary tree cannot have more than two children.'\
+                           unless (0..1).include? at_index
 
-      @children[at_index]        = child
-      @children_hash[child.name] = child if child # Assign the name mapping
-      child.parent               = self if child
+      old_child = @children[at_index]
+      if old_child && old_child != child
+        still_present = @children.each_with_index.any? do |existing, idx|
+          idx != at_index && existing.equal?(old_child)
+        end
+
+        unless still_present
+          @children_hash.delete(old_child.name)
+          old_child.set_as_root!
+        end
+      end
+
+      if child
+        child.parent&.remove!(child) unless child.parent == self
+        @children[at_index]        = child
+        @children_hash[child.name] = child # Assign the name mapping
+        child.parent               = self
+      else
+        @children[at_index] = nil
+      end
       child
     end
 
diff --git a/lib/tree/version.rb b/lib/tree/version.rb
index 167e679..dd7e64e 100644
--- a/lib/tree/version.rb
+++ b/lib/tree/version.rb
@@ -35,5 +35,5 @@
 
 module Tree
   # Rubytree Package Version
-  VERSION = '2.1.1'
+  VERSION = '2.2.0'
 end
diff --git a/rubytree.gemspec b/rubytree.gemspec
index af7e3c4..97958b3 100644
--- a/rubytree.gemspec
+++ b/rubytree.gemspec
@@ -44,7 +44,8 @@ Gem::Specification.new do |s|
   END_DESC
 
   s.metadata = {
-    'rubygems_mfa_required' => 'true'
+    'rubygems_mfa_required' => 'true',
+    'github_repo' => 'ssh://github.com/evolve75/rubytree'
   }
 
   s.files                = Dir['lib/**/*.rb']  # The actual code
diff --git a/test/test_binarytree.rb b/test/test_binarytree.rb
index f89755d..7d4b820 100755
--- a/test/test_binarytree.rb
+++ b/test/test_binarytree.rb
@@ -229,6 +229,9 @@ def test_left_child_equals
       assert_nil(@root.left_child, 'The left child should now be nil')
       assert_nil(@root.first_child, 'The first child is now nil')
       assert_equal('B Child at Right', @root.last_child.name, 'The last child should now be the right child')
+      assert(@left_child1.root?, 'The old left child should now be a root')
+      assert_nil(@left_child1.parent, 'The old left child should not have a parent')
+      assert_nil(@root['A Child at Left'], 'Lookup by old left name should be nil')
     end
 
     # Test right_child= method.
@@ -249,6 +252,15 @@ def test_right_child_equals
       assert_nil(@root.right_child, 'The right child should now be nil')
       assert_equal('A Child at Left', @root.first_child.name, 'The first child should now be the left child')
       assert_nil(@root.last_child, 'The first child is now nil')
+      assert(@right_child1.root?, 'The old right child should now be a root')
+      assert_nil(@right_child1.parent, 'The old right child should not have a parent')
+      assert_nil(@root['B Child at Right'], 'Lookup by old right name should be nil')
+    end
+
+    # Test invalid index error for set_child_at.
+    def test_set_child_at_invalid_index
+      error = assert_raise(ArgumentError) { @root.send(:set_child_at, @left_child1, 2) }
+      assert_match(/cannot have more than two children/i, error.message)
     end
 
     # Test isLeft_child? method.
@@ -297,5 +309,27 @@ def test_swap_children
       assert_equal(@right_child1, @root[0], 'right_child1 should now be the first child')
       assert_equal(@left_child1, @root[1], 'left_child1 should now be the last child')
     end
+
+    # Test traversals when nil children exist.
+    def test_traversal_with_nil_children
+      @root << @left_child1
+      @root << @right_child1
+
+      @root.right_child = nil
+
+      breadth_nodes = []
+      post_nodes = []
+
+      assert_nothing_raised do
+        @root.breadth_each { |node| breadth_nodes << node }
+      end
+
+      assert_nothing_raised do
+        @root.postordered_each { |node| post_nodes << node }
+      end
+
+      assert_equal([@root, @left_child1], breadth_nodes)
+      assert_equal([@left_child1, @root], post_nodes)
+    end
   end
 end
diff --git a/test/test_tree.rb b/test/test_tree.rb
index c56da69..d2fed98 100755
--- a/test/test_tree.rb
+++ b/test/test_tree.rb
@@ -94,6 +94,7 @@ def test_root_setup
       assert_not_nil(@root.name, 'Name should not be nil')
       assert_equal('ROOT', @root.name, "Name should be 'ROOT'")
       assert_equal('Root Node', @root.content, "Content should be 'Root Node'")
+      assert(@root.to_s.include?('Content: Root Node'), 'to_s should include content value')
       assert(@root.root?, 'Should identify as root')
       assert(!@root.children?, 'Cannot have any children')
       assert(@root.content?, 'This root should have content')
@@ -117,6 +118,11 @@ def test_root
       assert_equal(2, @root.node_height, "Root's height after adding the children should be 2")
     end
 
+    def test_to_s_empty_content
+      empty = Tree::TreeNode.new('EMPTY')
+      assert_match(/Content: <Empty>/, empty.to_s)
+    end
+
     def test_from_hash
       #      A
       #    / | \
@@ -491,6 +497,10 @@ def test_add
 
       # Test the addition of a nil node.
       assert_raise(ArgumentError) { @root.add(nil) }
+
+      # Test adding an ancestor as a child (cycle prevention).
+      error = assert_raise(ArgumentError) { @child4.add(@child3) }
+      assert_match(/Attempting add ancestor as a child/, error.message)
     end
 
     # Test the addition of a duplicate node (duplicate being defined as a node with the same name).
@@ -689,6 +699,16 @@ def test_remove_all_bang
 
       assert(!@root.children?, 'Should have no children')
       assert_equal(1, @root.size, 'Should have one node')
+
+      # Removed children should be detached (root? == true).
+      assert(@child1.root?, 'Child1 should be a root after remove_all!')
+      assert(@child2.root?, 'Child2 should be a root after remove_all!')
+      assert(@child3.root?, 'Child3 should be a root after remove_all!')
+      assert(@child4.root?, 'Child4 should be a root after remove_all!')
+      assert_nil(@child1.parent, 'Child1 parent should be nil after remove_all!')
+      assert_nil(@child2.parent, 'Child2 parent should be nil after remove_all!')
+      assert_nil(@child3.parent, 'Child3 parent should be nil after remove_all!')
+      assert_nil(@child4.parent, 'Child4 parent should be nil after remove_all!')
     end
 
     # Test the remove_from_parent! method.
@@ -832,6 +852,18 @@ def test_each_leaf
       assert(result_array.include?(@child4), 'Should have child 4')
     end
 
+    # Test the each_level method without a block (Enumerator).
+    def test_each_level
+      setup_test_tree
+
+      levels = @root.each_level.to_a
+
+      assert_equal(3, levels.length, 'Should have three levels')
+      assert_equal([@root], levels[0])
+      assert_equal([@child1, @child2, @child3], levels[1])
+      assert_equal([@child4], levels[2])
+    end
+
     # Test the parent method.
     def test_parent
       setup_test_tree
@@ -1531,6 +1563,9 @@ def test_rename_child
 
       assert_raise(ArgumentError) { @root.rename_child('Not_Present_Child1', 'ALT_Child1') }
 
+      error = assert_raise(ArgumentError) { @root.rename_child('Child1', 'Child2') }
+      assert_match(/Child name already exists: Child2/, error.message)
+
       @root.rename_child('Child1', 'ALT_Child1')
       assert_equal('ALT_Child1', @child1.name, "Name should be 'ALT_Child1'")
       assert_equal(@child1, @root['ALT_Child1'], 'Should be able to access from parent using new name')