Default to native transport on CRuby 4.0+

[lloeki]

What does this PR do?

Enable native trace transport by default on CRuby 4.0.0+, preserving explicit overrides and unsupported-platform fallback.

Motivation:

Start a version-gated rollout.

Change log entry

Begin the progressive rollout of the native trace exporter, enabling it by default on CRuby 4.0.0 and later.

Additional Notes:

master
  └─ #6433 shared fixes — default false
       ├─ #6419 progressive — CRuby ≥4.0.0
       └─ #6426 unconditional — default true

Shared fixes · Progressive · Unconditional

All target master; either rollout includes the shared fixes. Registry metadata still needs confirmation.

How to test the change?

Ruby 2.5.9 and 4.0.1: 301 configuration/component and 189 native examples, 0 failures. Cohort boundaries use runtime stubs. RuboCop, Steep, and changelog schema checks passed locally.

Ruby 4.0.1 full main suite: 6,547 examples, 0 failures.

[datadog-prod-us1-3]

 

❌ Errors

Your PR has failed checks. Please review the issues below and take necessary action before merging.

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Static Analysis | bundler-audit — 🔧 Needs a code fix, caused by this PR

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ℹ️ Info

No other issues found (see more)

🧪 All tests passed
❄️ No new flaky tests detected

🎯 Code Coverage (details)
• Patch Coverage: 96.55%
• Overall Coverage: 90.86% (+0.20%)

Useful? React with 👍 / 👎

_{This comment will be updated automatically if new data arrives.
🔗 Commit SHA: 112099f | Docs | View more details | Give us feedback!}

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-10-05T15:28:30.318169Z	a4324d0	Draft marked ready
🔒 Security Review	✅ Completed 2026-10-05T15:31:30.947965Z	a4324d0	Draft marked ready

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review" or "@codex security review".

Codex reacts with 👀 while any review is running, comments if it has suggestions, and reacts with 👍 once all reviews finish with no findings.

[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: a4324d0ea3

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".

[pr-commenter]

Benchmarks

Benchmark execution time: 2026-10-07 08:52:28

Comparing candidate commit 112099f in PR branch lloeki/native-transport-rollout with baseline commit 8a3b01c in branch master.

📊 Benchmarking dashboard

Found 0 performance improvements and 0 performance regressions! Performance is the same for 52 metrics, 0 unstable metrics.

Explanation

This is an A/B test comparing a candidate commit's performance against that of a baseline commit. Performance changes are noted in the tables below as:

• 🟩 = significantly better candidate vs. baseline
• 🟥 = significantly worse candidate vs. baseline

We compute a confidence interval (CI) over the relative difference of means between metrics from the candidate and baseline commits, considering the baseline as the reference.

If the CI is entirely outside the configured SIGNIFICANT_IMPACT_THRESHOLD (or the deprecated UNCONFIDENCE_THRESHOLD), the change is considered significant.

Feel free to reach out to #apm-benchmarking-platform on Slack if you have any questions.

More details about the CI and significant changes

You can imagine this CI as a range of values that is likely to contain the true difference of means between the candidate and baseline commits.

CIs of the difference of means are often centered around 0%, because often changes are not that big:

---------------------------------(------|---^--------)-------------------------------->
                              -0.6%    0%  0.3%     +1.2%
                                 |          |        |
         lower bound of the CI --'          |        |
sample mean (center of the CI) -------------'        |
         upper bound of the CI ----------------------'

As described above, a change is considered significant if the CI is entirely outside the configured SIGNIFICANT_IMPACT_THRESHOLD (or the deprecated UNCONFIDENCE_THRESHOLD).

For instance, for an execution time metric, this confidence interval indicates a significantly worse performance:

----------------------------------------|---------|---(---------^---------)---------->
                                       0%        1%  1.3%      2.2%      3.1%
                                                  |   |         |         |
       significant impact threshold --------------'   |         |         |
                      lower bound of CI --------------'         |         |
       sample mean (center of the CI) --------------------------'         |
                      upper bound of CI ----------------------------------'

[anmarchenko]

Hi! I tested the native transport setting with datadog-ci gem and discovered that it breaks datadog-ci's own transport.

The reason is that this code in build_writer method doesn't respect existing transport option:

        if settings.tracing.native_transport && (transport = build_native_transport(agent_settings))
          options = options.merge(transport: transport)
        end

It always replaces the transport with native without checking if another transport was configured.

[anmarchenko]

tested again - compatibility issue with datadog-ci gem is fixed, thank you!