diff --git a/lib/context_dev/internal/util.rb b/lib/context_dev/internal/util.rb
index 1c922103..ae1af068 100644
--- a/lib/context_dev/internal/util.rb
+++ b/lib/context_dev/internal/util.rb
@@ -428,7 +428,7 @@ def close
             @stream.to_a.join
           in Integer
             @buf << @stream.next while @buf.length < max_len
-            @buf.slice!(..max_len)
+            @buf.slice!(0, max_len)
           end
         rescue StopIteration
           @stream = nil
@@ -456,7 +456,7 @@ def read(max_len = nil, out_string = nil)
               read
             end
           end
-            .tap(&@blk)
+            .tap { @blk&.call(_1) }
         end
 
         # @api private
diff --git a/test/context_dev/internal/util_test.rb b/test/context_dev/internal/util_test.rb
index 1dfca4d2..7f441f3c 100644
--- a/test/context_dev/internal/util_test.rb
+++ b/test/context_dev/internal/util_test.rb
@@ -673,3 +673,29 @@ def test_decode_sse
     end
   end
 end
+
+class ContextDev::Test::UtilReadIOAdapterTest < Minitest::Test
+  def test_read_with_max_len
+    enum = ["hello ", "world"].to_enum
+    adapter = ContextDev::Internal::Util::ReadIOAdapter.new(enum)
+
+    chunk1 = adapter.read(3)
+    assert_equal("hel", chunk1)
+    assert_equal(3, chunk1.bytesize)
+
+    chunk2 = adapter.read(4)
+    assert_equal("lo w", chunk2)
+    assert_equal(4, chunk2.bytesize)
+
+    chunk3 = adapter.read(10)
+    assert_equal("orld", chunk3)
+
+    assert_nil(adapter.read(5))
+  end
+
+  def test_read_without_block
+    adapter = ContextDev::Internal::Util::ReadIOAdapter.new("sample content")
+    assert_equal("sample", adapter.read(6))
+    assert_equal(" content", adapter.read)
+  end
+end