ci: route test-only macOS lanes through MACOS_RUNNER_TESTS

[teamleaderleo]

Summary

At about 04:30Z on 2026-09-24, Blacksmith macOS 26 had 50 jobs queued and every other pool had none. Once the stale PR runs and E2E dispatches were cleared, most of what remained came from lanes that fall back to that pool:

• test-ios.yml simulator dispatches
• auth-refresh-tests.yml
• iroh-v2.yml

These lanes route through MACOS_RUNNER_IOS and MACOS_RUNNER_26, which are unset. Those same two variables also route release.yml, nightly.yml, ios-testflight.yml and the App Store upload, so setting them to move test traffic would also move signing.

This PR changes three things:

• test-ios.yml (with runner: auto), auth-refresh-tests.yml and the iroh-v2.yml client now read MACOS_RUNNER_TESTS first, then fall back to their old variable and label. If MACOS_RUNNER_TESTS is unset, routing is unchanged. MACOS_RUNNER_TESTS already routes test-e2e.yml and test-macos-suite.yml, and it is now set to macos-26.
• Every job that reads MACOS_RUNNER_TESTS now starts with a Verify GitHub-hosted route step, the same check the PR app-host shards run since ci: run macOS jobs on GitHub-hosted runners alongside Blacksmith #14097. The self-hosted fleet also carries a macos-26 label, so a macos-* request that lands anywhere other than runner.environment == github-hosted fails before checkout. runner_label_policy.py flags macos-26 for the same reason.
• app-host-test-rerun.yml no longer follows MACOS_RUNNER_TESTS. A rerun builds the test bundle with the exact Xcode path recorded in the products receipt, and select-ci-xcode.sh fails if that path is missing. Setting the variable to macos-26 would have sent reruns to an image that may not carry that Xcode, so the rerun stays on Blacksmith macOS 15, where it ran before.

docs/ci-runners.md describes the new scope of the variable. The self-hosted guard's pinned test-ios.yml expressions are updated to match.

Testing

• actionlint is clean on all six workflows.
• tests/test_ci_self_hosted_guard.sh passes (exit 0).
• These also pass:
  • test_run_e2e.py
  • test_app_host_test_rerun.py
  • test_runner_label_policy.py
  • test_ci_fork_runner_routing.py
  • test_ci_change_areas.py
  • test_ci_actionlint_covers_every_workflow.py
  • test_ci_reusable_workflow_permissions.py
  • the E2E, iOS and app-host workflow tests that read these files
• Not yet exercised: an actual iOS simulator run on hosted macos-26. A dispatch that asks for an exact simulator runtime the hosted image doesn't carry will fail at simulator selection. runner: blacksmith-6vcpu-macos-26 still forces the old pool.

Checklist

• I added or updated tests for behavior changes
• I updated docs/changelog if needed

🤖 Generated with Claude Code

https://claude.ai/code/session_01EduXdN9PKnGsMQztJK7WeE

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Generated by Claude Code

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Summary by cubic

Relieves the Blacksmith macOS 26 pool backlog by routing test-only macOS lanes through MACOS_RUNNER_TESTS instead of MACOS_RUNNER_IOS and MACOS_RUNNER_26.

• test-ios.yml (auto) and the iroh-v2.yml client now read MACOS_RUNNER_TESTS first and fall back to their previous variable or label; if unset, routing is unchanged. auth-refresh-tests.yml stays on main's dual-Xcode runner and doesn't follow the variable.
• MACOS_RUNNER_IOS and MACOS_RUNNER_26 also route release, nightly, TestFlight, and App Store signing, so they can't be flipped to move test traffic.
• Every job reading MACOS_RUNNER_TESTS now fails before checkout if a macos-* request lands on anything other than GitHub-hosted capacity, since the self-hosted fleet also carries a macos-26 label. In test-e2e.yml the check validates the label chosen by its separate runner-selection job.
• app-host-test-rerun.yml no longer follows MACOS_RUNNER_TESTS: reruns must build with the exact Xcode recorded in the products receipt, so they stay on the Blacksmith macOS 15 pool.

^{Written for commit c4aa4ec. Summary will update on new commits.}

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📥 Commits

Reviewing files that changed from the base of the PR and between 832f621 and c4aa4ec.

📒 Files selected for processing (7)

• .github/workflows/app-host-test-rerun.yml
• .github/workflows/iroh-v2.yml
• .github/workflows/test-e2e.yml
• .github/workflows/test-ios.yml
• .github/workflows/test-macos-suite.yml
• docs/ci-runners.md
• tests/test_ci_self_hosted_guard.sh

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