Ruby 4 compatibility issues

[arielvalentin]

CGI has been removed from the standard library and must be required as a gem dependency¹. This requires users to add the CGI dependency explicitly when using the Anthropic SDK in a standalone Ruby library otherwise the gem fails with a runtime error²:

NoMethodError: undefined method 'parse' for class CGI
      /opt/hostedtoolcache/Ruby/4.0.0/x64/lib/ruby/gems/4.0.0/gems/anthropic-1.16.2/lib/anthropic/internal/util.rb:275:in 'Anthropic::Internal::Util.decode_query'
      /opt/hostedtoolcache/Ruby/4.0.0/x64/lib/ruby/gems/4.0.0/gems/anthropic-1.16.2/lib/anthropic/internal/util.rb:296:in 'Anthropic::Internal::Util.parse_uri'
      /opt/hostedtoolcache/Ruby/4.0.0/x64/lib/ruby/gems/4.0.0/gems/anthropic-1.16.2/lib/anthropic/internal/transport/base_client.rb:209:in 'Anthropic::Internal::Transport::BaseClient#initialize'
      /opt/hostedtoolcache/Ruby/4.0.0/x64/lib/ruby/gems/4.0.0/gems/anthropic-1.16.2/lib/anthropic/client.rb:126:in 'Anthropic::Client#initialize'

anthropic-sdk-ruby/lib/anthropic/internal/util.rb

Line 275 in 7bbf5a4

CGI.parse(query.to_s)

Ideally the anthropic SDK should declare the CGI gem as a dependency to avoid requiring users to explicitly add transitive dependencies in their Gemfiles or gemspecs.

Footnotes

1. https://www.ruby-lang.org/en/news/2025/12/25/ruby-4-0-0-released/#stdlib-compatibility-issues ↩

2. https://github.com/open-telemetry/opentelemetry-ruby-contrib/actions/runs/20697089280/job/59413961169?pr=1903#step:3:181 ↩

[jslabovitz]

Unfortunately this is not enough, as the SDK uses CGI.parse, which has not been implemented in the CGI stubs.

I made this change in my local clone and it seemed to work:

diff --git lib/anthropic/internal/util.rb lib/anthropic/internal/util.rb
index 38e3b647..af3e3caa 100644
--- lib/anthropic/internal/util.rb
+++ lib/anthropic/internal/util.rb
@@ -272,7 +272,7 @@ module Anthropic
         #
         # @return [Hash{String=>Array<String>}]
         def decode_query(query)
-          CGI.parse(query.to_s)
+          URI.decode_www_form(query.to_s).to_h.transform_values(&:to_s)
         end

         # @api private

(The transform_values(&:to_s) is because it appears that URI.decode_www_form converts all-digit strings to numbers, where CGI.parse left them as strings. This difference bit me in my own code that uses the SDK, so figured it was probably important to handle that compatibility case.)

I'm sorry I can't submit a pull request, as I can't set up my environment for all the testing at the moment, so couldn't pass the CONTRIBUTING.md requirements. I hope this helps anyway.

[jslabovitz]

By the way, I think using the URI methods means you don't need to include the CGI module for the SDK itself. It still seems to be needed for tests (see FakeCGI) but maybe this could be rewritten to avoid requiring the cgi gem at all?