fix: shorten multipart boundary sep to less than RFC specificed max length

Author: stainless-app[bot]

lib/openai/internal/util.rb

@@ -566,7 +566,8 @@ class << self
         #
         # @return [Array(String, Enumerable<String>)]
         private def encode_multipart_streaming(body)
-          boundary = SecureRandom.urlsafe_base64(60)
+          # RFC 1521 Section 7.2.1 says we should have 70 char maximum for boundary length
+          boundary = SecureRandom.urlsafe_base64(46)
 
           closing = []
           strio = writable_enum do |y|

test/openai/internal/util_test.rb

@@ -213,6 +213,18 @@ def env_table
     end
   end
 
+  def test_encoding_length
+    headers, = OpenAI::Internal::Util.encode_content(
+      {"content-type" => "multipart/form-data"},
+      Pathname(__FILE__)
+    )
+    assert_pattern do
+      headers.fetch("content-type") => /boundary=(.+)$/
+    end
+    field, = Regexp.last_match.captures
+    assert(field.length < 70 - 6)
+  end
+
   def test_file_encode
     file = Pathname(__FILE__)
     headers = {"content-type" => "multipart/form-data"}