Fix broken PR workflow around API diffs for fork PRs - #2291
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Jevan Saks (jevansaks) merged 2 commits intoAug 25, 2026
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Skip API diff comment steps for cross-repository pull requests, whose GITHUB_TOKEN is read-only, while preserving validation and artifact uploads. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: c89a1dcf-0af3-4f7c-ad60-69a9866eeffd
Move PR comment publishing to a trusted workflow_run workflow that consumes the validation artifact without executing contributor code. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: c89a1dcf-0af3-4f7c-ad60-69a9866eeffd
Jevan Saks (jevansaks)
marked this pull request as ready for review
August 25, 2026 02:18
Jevan Saks (jevansaks)
requested review from
a team and
Vineeth Thomas Alex (vineeththomasalex)
as code owners
August 25, 2026 02:18
Jevan Saks (jevansaks)
enabled auto-merge (squash)
August 25, 2026 02:20
Manodasan Wignarajah (manodasanW)
approved these changes
Aug 25, 2026
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Summary
pull_requestsecurity boundary.workflow_runworkflow to download that artifact and post or update the API-diff PR comment for both fork and same-repository contributions.Why
Fork PR workflows receive a read-only
GITHUB_TOKEN, even when the workflow requestspull-requests: write. The validation in #2290 completed successfully, then the no-diff comment step failed with403 Resource not accessible by integration.Granting the untrusted PR workflow write access would be unsafe. The split workflow follows GitHub's recommended pattern: untrusted code builds and uploads data with read-only permissions, while trusted workflow code on the default branch performs the privileged comment operation without checking out or executing contributor code.
The trusted workflow resolves the PR from the run's fork owner, branch, and exact head SHA because GitHub does not populate
workflow_run.pull_requestsfor these fork runs.Validation
git diff --checkactionlint .github/workflows/pr-validation.yml .github/workflows/pr-api-diff-comment.ymlgithub-scriptJavaScript syntax check with Node.jswinmdartifact and confirmed it contains the expected zero-lengthapi-diff.patchfor the no-diff result.danfiedler-msft:danfiedler/pin-actionsand its exact workflow head SHA.The
workflow_runjob itself can only execute after this workflow definition exists on the default branch, which is the GitHub security boundary that gives the trusted follow-up workflow write permission.