[teamleaderleo]

"Place the light jobs on a free mini", at the end of build-nightly-app, only offers glaeda-side-* labels. The all-nightly reservation's light runners (glaeda-nightly-only-m4pro, four per dedicated Mac) exist for these jobs, but they never qualified. So on every nightly-next run the step waited its full three minutes on busy side minis, re-reading runners every 30 s, and then sent prepare-nightly-variant-primary, prepare-nightly-variant and await-nightly-tree-marker to Blacksmith anyway.

That wait sits on the path from landing to feed, and the rule allows 30 minutes for that path (the feed was about 45 min behind tonight).

Change (scripts/ci/portable_job_placement.py and the step's env in nightly.yml):

• New NIGHTLY_ONLY_LABEL (vars.CI_NIGHTLY_ONLY_RUNNER). On a nightly placement whose runners were read, attempt 1 only (the same attempt rule, factored into attempt_refusal), the jobs take the reservation's idle runners at once.
• Idle runners are counted less the jobs the snapshot shows queued on that label. The warm builder carries only glaeda-nightly-only-m4pro-builder, so it is never counted.
• When the reservation is unset, busy or unread, or on a later attempt, the existing side, wait and Blacksmith logic runs unchanged.
• The three jobs use no secrets and no environment, and the reservation already admits nightly.yml jobs on nightly-next (decide, resolve and "build nightly inputs" run there today).

Performance

metric	before	after	delta	harness or run link
"Place the light jobs on a free mini" duration	186 s (runs 41354494707, 41355147140, 41356701375)	under 15 s (run 41360732074: the three jobs took glaeda-nightly-only-m4pro)	about -3 min per build	build-nightly-app step timings
runner reads in that step	about 42 REST requests (github_spend)	4 requests (run 41360732074)	about -38 requests per run	github_spend lines

Tests:

• tests/test_ci_portable_job_placement.py: 36 pass, including new NightlyOnly cases for placement, the queue count, never the builder, the busy, unread, unset and later-attempt fallbacks, and the workflow wiring.
• tests/test_ci_nightly_off_blacksmith.py: 21 pass.
• test_ci_linux_single_size fails the same way on base (cmux-next-base-tier-kick, cmux-next-dev-kick, ios-internal-nightly-trigger).

Agent session: agent session

🤖 Generated with Claude Code

[github-actions]

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

Review 226ac57: 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=pr31410 -f ref=lane/nightly-light-placement -f platform=macos -f backend_mode=local

red: cmux-next checks (god files, concurrency, crash safety, l10n); no finished base run on c4a9ee3 to compare; do not merge until green; see lane-rules

Shipped in:

• cmux NEXT nightly 1.0.0-nightly.4136073207401 (9a8633089c)
• cmux NEXT nightly 1.0.0-nightly.4136174016701 (6a6302bf13)

[teamleaderleo]

Review (subagent claude-opus-5-5 medium): SHIP at 226ac57

• When the reservation has room, all three light jobs are placed on the first pass and the loop exits.
• When runners can't be read, the new branch is skipped and the old path runs.
• The runs-on wiring (light_mini_runner, light_mini_jobs, light_attempt) works with the reservation label, and the warm builder label is never counted.
• The three jobs use no secrets and no environment, with contents: read.
• Passing: placement, nightly_off_blacksmith, nightly_trusted_routing, runner_label_policy, runner_routing_table, fork_runner_routing, feat_ci_guard_group, route_refusal_detail, nightly_push_throttle.
• test_ci_self_hosted_guard.sh and test_ci_linux_single_size fail the same way on base.

Follow-ups:

• [follow-up] With only partial room, the wait loop can switch between the reservation and the side route on later passes. Keep reservation placements once made, and let the side route take only what's left.
• [follow-up] read() only reads runners when eligible() passes, which needs SIDE_LABEL to be an owned side label. Let it also read when NIGHTLY=1 and NIGHTLY_ONLY_LABEL is set.
• [follow-up] Pin NIGHTLY_ONLY_LABEL to nightly_build_runner.NIGHTLY_ONLY_LABEL, and check that the janitor snapshot has a pools entry for that label.