[sdf-jkl]

WIP — not ready for review or merge. This is a fork-CI experiment. A merge queue with required upstream validation should be established before this is ready to land; this PR does not add that gate.

Rationale for this change

Reduce repeated heavy builds in Apache's shared runner pool by running development iterations in contributor forks, following apache/arrow-rs#11788 and apache/datafusion#25591.

What changes are included in this PR?

Route external PR builds targeting main to contributor forks across regular language, documentation, release-validation, and requested Extra workflows. Retain Arrow's specialized CUDA and large-memory runners upstream. Mirror results as informational per-workflow checks and provide a manual CI: Upstream fallback.

Before review:

• Establish the merge queue and required checks; the current label fallback does not enforce pre-merge validation.
• Resolve macOS placement. This prototype still runs macOS in forks; [Discuss] Mac testing on fork branches keeps failing arrow-rs#11976 and ci: Skip macOS checks in forks arrow-rs#11991 support retaining upstream coverage instead.
• Validate status mirroring end to end, reduce the diff where possible, and establish an Arrow tracking issue.

Are these changes tested?

46 local routing/reporter tests pass. Fork runs at bfe477b66 passed Archery, lint, both documentation workflows, integration, R, and RC. C++ and other workflows remain incomplete, with macOS jobs queued.

Known failures: the release test lacked an upstream tag (the fork has since been synced, but the failed job has not rerun); C++ Extra encountered missing Abseil symbols when linking the static S3 example. Live upstream status mirroring remains unverified.

Are there any user-facing changes?

No library API changes. Contributors would enable Actions and run/rerun builds in their forks. Fork results test the branch head and are informational, not an enforced merge gate.

Was AI used for this PR?

Codex generated and self-reviewed the workflow port, tests, documentation, and this description. Human code review is pending.

PR code and description written by:

• Human
• AI

Reviewed before submission by:

• Human
• AI
• Not reviewed

[github-actions]

Thanks for opening a pull request!

This pull request has been automatically converted to a draft because its title doesn't match Arrow's required format.

If this is not a minor PR, could you open an issue for this pull request on GitHub? https://github.com/apache/arrow/issues/new/choose

Opening GitHub issues ahead of time contributes to the Openness of the Apache Arrow project.

Then could you also rename the pull request title in the following format?

GH-${GITHUB_ISSUE_ID}: [${COMPONENT}] ${SUMMARY}

or

MINOR: [${COMPONENT}] ${SUMMARY}

After updating the title, you can mark the pull request as ready for review.

See also:

• Other pull requests
• Contribution Guidelines - Contributing Overview