[CI Broken] BuildKite CI not running or not reporting status

[ChrisRackauckas-Claude]

Summary

BuildKite CI appears to be either not running or not properly integrated with GitHub's status check API.

Evidence

1. No Status Checks Visible

After creating PR #46 (CI Health Check) and waiting over 2 hours:

• GitHub API returns "statusCheckRollup": null for all PRs, including the health check PR
• gh pr checks 46 reports: "no checks reported on the 'main' branch"
• No CI status indicators appear on any PRs (checked PRs CI Health Check - Automated Testing #46, Improve explicit imports hygiene #45, Add automatic sparsity detection for MCP problems #44)

2. BuildKite Configuration Exists

The repository has BuildKite configuration in .buildkite/pipeline.yml with:

• Format check step
• CPU test matrix (Core, Applications, QA)
• CUDA test matrix (Core, Applications)
• All configured to run unless [skip tests] is in commit message

3. Recent PR Merge Patterns

• PR Improve explicit imports hygiene #45 (merged 2025-12-29): created at 21:33:43Z, merged at 21:54:22Z (21 minutes)
• This is suspiciously fast if full CI test suite was required to pass

4. BuildKite Integration History

• BuildKite was added in PR Move CI to Buildkite #30 (merged 2023-07-21)
• Configuration has been in place for over a year

Root Cause Analysis

Possible causes:

1. BuildKite webhook not configured: GitHub may not be triggering BuildKite builds on PR creation/updates
2. BuildKite status integration disabled: BuildKite builds may run but not report status back to GitHub
3. BuildKite pipeline disabled: The BuildKite pipeline may be paused or disabled in BuildKite's dashboard
4. Authentication/permissions issue: BuildKite may lack permissions to update GitHub PR status
5. Fork PR restrictions: BuildKite may not be configured to run on PRs from forks (like PR CI Health Check - Automated Testing #46 from ChrisRackauckas-Claude fork)

Impact

• No automated testing verification before merging PRs
• Potential for broken code to be merged into main branch
• Loss of CI safety net for quality assurance

Suggested Fix Approach

1. Verify BuildKite pipeline status:

   • Check BuildKite dashboard to see if pipeline exists and is enabled
   • Verify webhook configuration between GitHub and BuildKite

2. Check GitHub integration:

   • Ensure BuildKite GitHub app is installed and has proper permissions
   • Verify BuildKite is configured to report commit statuses

3. Test with direct push:

   • Try pushing directly to a branch (not from fork) to rule out fork-related issues

4. Review BuildKite settings:

   • Check if there are restrictions on which branches/PRs trigger builds
   • Verify that the BuildKite organization/pipeline is still active

Additional Context

• Health check PR: CI Health Check - Automated Testing #46
• CI configuration: .buildkite/pipeline.yml
• Last known working CI: Unknown (no recent evidence of CI actually running)

cc @ChrisRackauckas

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Discovered during automated CI health check on 2025-12-30