[teamleaderleo]

Leo, 2026-10-27: "BUT WTF COULD POSSIBLY BE MORE IMPORTANT ON OUR FUCKING MINIS". The standing order: a waiting nightly job is admitted on a mini ahead of every PR, DEV and side job.

Why

GitHub hands a queued job to the next idle runner in arrival order. So nightly-next's build-nightly-app, queued on the shared side label, waits behind every PR job queued there first. Run 40518198747 shows it: queued on glaeda-side-light-xcode-26.6 at 14:08Z, never acquired by a runner, moved to Blacksmith at 14:12Z, and still queued there at 14:28Z. At that time the std side label had 18 of 18 runners busy and the light side label 19 of 19.

glaeda#1684 adds a nightly slot: one runner per mini, labelled glaeda-nightly-std-xcode-26.6, that takes only nightly jobs. Its gate listens however full the mini is, and its job waits first in line on the mini, with every other runner there held.

What

owned_label() in nightly_build_runner.py also accepts glaeda-nightly-<class>-xcode-<version>. With vars.CI_NIGHTLY_NEXT_BUILD_RUNNER set to that label, the picker's order becomes:

1. the dedicated builder;
2. an idle nightly slot;
3. the side label;
4. Blacksmith.

Main's rescue watches the label through the main PR beside this one, which lands first.

Tests

tests/test_nightly_build_runner.py: 24 OK, including the new test_the_nightly_slot_comes_first_while_idle (an idle slot wins, a busy slot falls back to the side label, and near-miss labels are rejected).

Risk

Low. Nothing changes until the variable names the label. The variable is set only after the slots are registered and main's rescue watches the label.

This touches the same owned_label lines as #26237, the dispatch and re-run routing. The new test works with or without owned_route's attempt argument, so either PR can land first.

Agent session: agent session

🤖 Generated with Claude Code

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[teamleaderleo]

Owned by an agent session · session

[github-actions]

cmux status _{(one comment, edited in place; each line is updated by the job that owns it)}

Review b1e90af: HQ feed card · gallery before/after runs · checks

App of this head (app.zip, kept 1 day)

gh workflow run reload-build.yml -R manaflow-ai/cmux --ref feat-cmux-next -f tag=pr26251 -f ref=fanout-infra/picker-nightly-slot -f platform=macos -f backend_mode=local

web and size checks: green

[teamleaderleo]

Bead cx-edqdlc created for this PR by the cmux coordinator.

[blacksmith-sh]

Found 2 test failures on Blacksmith runners:

Failures

Test	View Logs
nightly.yml must derive the embedded key and sign every appcast through the helper/ nightly.yml must derive the embedded key and sign every appcast through the helper	View Logs
test_the_repository_highlights_validate (main.DigestTests.test_the_repository_highl ights_validate)/ test_the_repository_highlights_validate (main.DigestTests.test_the_repository_highl ights_validate)	View Logs

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[github-actions]

Shipped in:

• cmux NEXT nightly 1.0.0-nightly.4055612617201 (f83ddd6b20)