diff --git a/lib/typeprof/core/ast/sig_type.rb b/lib/typeprof/core/ast/sig_type.rb
index 263abf1aa..ad3e3a415 100644
--- a/lib/typeprof/core/ast/sig_type.rb
+++ b/lib/typeprof/core/ast/sig_type.rb
@@ -258,9 +258,24 @@ def covariant_vertex0(genv, changes, vtx, subst)
         changes.add_depended_static_read(@static_ret.last)
         tae = @static_ret.last.type_alias_entity
         if tae && tae.exist?
+          # Check for recursive expansion
+          expansion_key = [@cpath, @name]
+          subst[:__expansion_stack__] ||= []
+
+          if subst[:__expansion_stack__].include?(expansion_key)
+            # Recursive expansion detected: this type alias references itself
+            # Stop expansion here to prevent SystemStackError. The type system
+            # will handle the incomplete expansion gracefully, typically by
+            # treating unresolved recursive references as 'untyped', which
+            # maintains type safety while allowing the program to continue.
+            return
+          end
+
           # need to check tae decls are all consistent?
           decl = tae.decls.each {|decl| break decl }
           subst0 = subst.dup
+          subst0[:__expansion_stack__] = subst[:__expansion_stack__].dup + [expansion_key]
+
           # raise if decl.params.size != @args.size # ?
           decl.params.zip(@args) do |param, arg|
             subst0[param] = arg.covariant_vertex(genv, changes, subst0) # passing subst0 is ok?
@@ -273,9 +288,24 @@ def contravariant_vertex0(genv, changes, vtx, subst)
         changes.add_depended_static_read(@static_ret.last)
         tae = @static_ret.last.type_alias_entity
         if tae && tae.exist?
+          # Check for recursive expansion
+          expansion_key = [@cpath, @name]
+          subst[:__expansion_stack__] ||= []
+
+          if subst[:__expansion_stack__].include?(expansion_key)
+            # Recursive expansion detected: this type alias references itself
+            # Stop expansion here to prevent SystemStackError. The type system
+            # will handle the incomplete expansion gracefully, typically by
+            # treating unresolved recursive references as 'untyped', which
+            # maintains type safety while allowing the program to continue.
+            return
+          end
+
           # need to check tae decls are all consistent?
           decl = tae.decls.each {|decl| break decl }
           subst0 = subst.dup
+          subst0[:__expansion_stack__] = subst[:__expansion_stack__].dup + [expansion_key]
+
           # raise if decl.params.size != @args.size # ?
           decl.params.zip(@args) do |param, arg|
             subst0[param] = arg.contravariant_vertex(genv, changes, subst0)
diff --git a/scenario/rbs/recursive-type-alias.rb b/scenario/rbs/recursive-type-alias.rb
new file mode 100644
index 000000000..4f64e407a
--- /dev/null
+++ b/scenario/rbs/recursive-type-alias.rb
@@ -0,0 +1,79 @@
+## update: test.rbs
+# Basic recursive type alias
+type context = nil | [context, bool]
+
+class C
+  def foo: -> context
+end
+
+## update: test.rb
+def test1
+  C.new.foo
+end
+
+## assert: test.rb
+class Object
+  def test1: -> [untyped, bool]?
+end
+
+## diagnostics: test.rb
+
+## update: test.rbs
+# Recursive type alias in class scope
+class D
+  type tree = Integer | [tree, tree]
+  def get_tree: -> tree
+end
+
+## update: test.rb
+def test2
+  D.new.get_tree
+end
+
+## assert: test.rb
+class Object
+  def test2: -> (Integer | [untyped, untyped])
+end
+
+## diagnostics: test.rb
+
+## update: test.rbs
+# Mutually recursive type aliases
+type node = [Integer, nodes]
+type nodes = Array[node]
+
+class E
+  def build_tree: -> node
+end
+
+## update: test.rb
+def test3
+  E.new.build_tree
+end
+
+## assert: test.rb
+class Object
+  def test3: -> [Integer, Array[untyped]]
+end
+
+## diagnostics: test.rb
+
+## update: test.rbs
+# Recursive type alias with generic parameters
+type list[T] = nil | [T, list[T]]
+
+class F
+  def create_list: -> list[String]
+end
+
+## update: test.rb
+def test4
+  F.new.create_list
+end
+
+## assert: test.rb
+class Object
+  def test4: -> [String, untyped]?
+end
+
+## diagnostics: test.rb