Add Ruby 4.0.0 support

[kwent]

Summary

Ruby 4.0.0 was released on December 25, 2025. The current gemspec restricts Ruby version to < 4.0:

required_ruby_version: >= 2.5.0, < 4.0

Request

Please update the gemspec to support Ruby 4.0.0.

Environment

• Ruby 4.0.0 (2025-12-25 revision 553f1675f3)
• Tested on macOS arm64

Error

Could not find compatible versions

Because datadog >= 2.23.0 depends on Ruby >= 2.5.0, < 4.0
  and Gemfile depends on datadog ~> 2.23,
  Ruby >= 2.5.0, < 4.0 is required.
So, because current Ruby version is = 4.0.0,
  version solving has failed.

Thank you!

[composerinteralia]

#5157 was merged, so I think this will get resolved by the next release.

[ivoanjo]

Hey 👋, indeed the bump to the gemspec is in master and we plan to release it soon! Thanks everyone for the patience + happy new year + happy new Ruby 4! :)

[jose-sherpa]

@ivoanjo I got so excited when I saw a release today 😢

[ivoanjo]

Ah @jose-sherpa we've indeed merged #5157! So folks here can start upgrading to 4.0 and experimenting with it :)

The only reason we haven't yet closed the issue is because of this tidbit in the release notes:

We've also introduced initial support for Ruby 4.0. While comprehensive validation is ongoing, we welcome any feedback if you encounter issues using this Ruby version.

That is, we want to make sure we do some more testing with Ruby 4.0.0 stable + dd-trace-rb before we call it very solid :)