#25351 ci(nightly): NEXT nightly Blacksmith macOS legs on 6vcpu, the size that gets capacity

The nightly-next feed is about 4 hours behind. Its Blacksmith macOS legs default to blacksmith-12vcpu-macos-26, and that label has started nothing since about 01:20Z on 2026-10-26.

Evidence, taken from the Actions API at about 05:40Z:

• 12vcpu: 36 jobs queued on blacksmith-12vcpu-macos-26, none running. The oldest has been waiting since 02:19Z. The last job that started on it was build-nightly-app in run 40249486409, at 01:20Z.
• 6vcpu: blacksmith-6vcpu-macos-26 kept starting jobs over the same window. Three fast-tier legs and a Swift canary started between 05:21Z and 05:25Z, and its oldest queued job was about 15 minutes old.
• Stuck nightly-next runs: 40264205435 (build-sign-notarize-nightly) and 40268415260 and 40268834029 (build-nightly-app, attempt 2) sit queued on the 12vcpu label.

The likely cause is that the org's Blacksmith macOS vCPU budget keeps being refilled by 6vcpu jobs, so a 12vcpu job never fits.

Change

• In nightly.yml, the default blacksmith-12vcpu-macos-26 becomes blacksmith-6vcpu-macos-26 in all 12 places. It is the same Blacksmith image, and Blacksmith is trusted for signing.
• vars.MACOS_RUNNER_26 still overrides it when set.
• Attempt-1 owned-pool routing (vars.CI_SIDE_LANE_RUNNER / CI_SEED_TRUSTED_POOL) is unchanged. Routing order is unchanged: owned Macs first, Blacksmith last.
• The tests that pin the nightly's default label are updated: test_ci_nightly_off_blacksmith, test_nightly_universal_build.sh, and test_nightly_unsigned_resume.

Risk

• Slower jobs: sign and notarize on 6 vCPU instead of 12. Those steps are mostly codesign, lipo and the Apple wait. A compile leg that falls back on attempt 2 or later (build-nightly-app or prepare fallback) is slower, but it starts instead of waiting forever.
• Timeouts: they stay the same (build-nightly-app 90 min, sign 160 min).
• Already-queued runs: this does not move them, because runs-on is fixed at queue time. They are not cancelled.

Tests (run locally, single files)

• Pass: test_ci_nightly_off_blacksmith, test_nightly_unsigned_resume, test_nightly_trusted_routing, test_ci_tui_routes_avoid_nightly_label, test_ci_next_macos_cascade, test_runner_label_policy, test_nightly_universal_build.sh.
• Fail, also on base: test_ci_fork_runner_routing. Its nightly.yml:3104 finding is the same line on base, just with the 12vcpu label.

Agent session: agent session

🤖 Generated with Claude Code

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