ci(nightly-next): the build picker may offer glaeda's nightly slot first

scripts/ci/nightly_build_runner.py

@@ -53,6 +53,7 @@
 
 import datetime as dt
 import os
+import re
 import sys
 import time
 from pathlib import Path
@@ -67,8 +68,15 @@
 # a refusal or a stuck queue there is re-run as attempt 2, which takes Blacksmith. The DEV compile
 # slot (glaeda-dev-*) is not one, so it is never offered: runs 40446901975 and 40448164753 died at
 # "Set up runner" on glaeda-dev-std-xcode-26.6 and nothing re-ran them.
+# glaeda's nightly slot (glaeda#1684, runner.nightlySlot): one runner per mini whose label no PR job asks for and
+# whose hook takes only nightly jobs, ahead of every job waiting on that mini. A build queued on the shared side label
+# waited behind every PR job queued there first (2026-10-27 14:08Z: run 40518198747 was never acquired on the light
+# side label). main's rescue watches it (owned_pool_rescue.LANE_LABEL), so vars.CI_NIGHTLY_NEXT_BUILD_RUNNER may name it.
+NIGHTLY_SLOT_LABEL = re.compile(r"glaeda-nightly-(?:xl|std|light)-xcode-[0-9]+(?:\.[0-9]+)*")
+
+
 def owned_label(label: str) -> bool:
-    return pool.persistent(label)
+    return pool.persistent(label) or bool(NIGHTLY_SLOT_LABEL.fullmatch(label or ""))
 
 
 # How long a run waits for the dedicated builder while it is busy, and how often it looks. Its

scripts/ci/runner_label_policy.py

@@ -171,10 +171,11 @@ def nightly_next_build_reason(label: str) -> str | None:
     nightly.yml's nightly-next app build reads it first, for every event and
     attempt. It may name an owned side or dev label (glaeda-side-<class>-... or
     glaeda-dev-<class>-...), the same trust as CI_SIDE_LANE_RUNNER, which that
-    build already takes. Anything else is held to the workflow policy. Empty is
-    fine (off).
+    build already takes, or glaeda's nightly slot (glaeda-nightly-<class>-...,
+    glaeda#1684): one runner per owned mini whose hook admits only nightly jobs.
+    Anything else is held to the workflow policy. Empty is fine (off).
     """
-    for prefix in (SIDE_LANE_PREFIX, "glaeda-dev-"):
+    for prefix in (SIDE_LANE_PREFIX, "glaeda-dev-", "glaeda-nightly-"):
         if label.startswith(prefix) and _owned_pattern().fullmatch("glaeda-" + label[len(prefix):]):
             return None
     return forbidden_reason(label)

tests/test_nightly_build_runner.py

@@ -67,6 +67,24 @@ def test_a_retry_unread_runners_or_a_non_owned_label_picks_no_owned_mac(self) ->
             with self.subTest(label=label):
                 self.assertEqual(picker.owned_route(label, idle, "1")[0], "")
 
+    def test_the_nightly_slot_comes_first_while_idle(self) -> None:
+        # vars.CI_NIGHTLY_NEXT_BUILD_RUNNER names glaeda's nightly slot, then the side label: an idle slot takes the
+        # build, and a busy one leaves it to the side label, never a wait.
+        slot = "glaeda-nightly-std-xcode-26.6"
+        self.assertTrue(picker.owned_label(slot))
+        for label in ("glaeda-nightly", "glaeda-nightly-std", "glaeda-nightlyx-std-xcode-26.6"):
+            self.assertFalse(picker.owned_label(label), label)
+        labels = f"{slot} {SIDE}"
+
+        def route(runners: list) -> str:  # attempt 1, with or without owned_route's attempt argument
+            try:
+                return picker.owned_route(labels, runners, "1")[0]
+            except TypeError:
+                return picker.owned_route(labels, runners)[0]
+
+        self.assertEqual(route([runner(SIDE), runner(slot)]), slot)
+        self.assertEqual(route([runner(SIDE), runner(slot, busy=True)]), SIDE)
+
     def test_a_label_the_rescue_does_not_watch_is_never_offered(self) -> None:
         # The DEV slot: a refusal there is never re-run (runs 40446901975, 40448164753).
         sys.path.insert(0, str(ROOT / "scripts" / "ci"))

tests/test_runner_label_policy.py

@@ -225,10 +225,12 @@ def test_every_runner_variable_a_workflow_reads_is_reported(self) -> None:
 class NightlyNextBuildVariable(unittest.TestCase):
     def test_an_owned_side_or_dev_label_or_blacksmith_is_allowed(self) -> None:
         name = "CI_NIGHTLY_NEXT_BUILD_RUNNER"
-        for label in ("glaeda-dev-std-xcode-26.6", "glaeda-side-std-xcode-26.6", "blacksmith-6vcpu-macos-26", ""):
+        for label in ("glaeda-dev-std-xcode-26.6", "glaeda-side-std-xcode-26.6", "glaeda-nightly-std-xcode-26.6",
+                      "blacksmith-6vcpu-macos-26", ""):
             with self.subTest(label=label):
                 self.assertEqual(drifted_runner_variables({name: label}), [])
-        for label in ("glaeda-std-xcode-26.6", "glaeda-runner-cmux7s-mac-mini-nightly-next", "self-hosted"):
+        for label in ("glaeda-std-xcode-26.6", "glaeda-runner-cmux7s-mac-mini-nightly-next", "self-hosted",
+                      "glaeda-nightly-nonsense", "glaeda-nightly-std"):
             with self.subTest(label=label):
                 self.assertTrue(drifted_runner_variables({name: label}))