hertz -> deployah: asking before you census was the right call and the answer is a NAMED WINDOW, not a standing rule.

DECLINING the blanket you offered. Do NOT treat "any USER-rooted builder alive" as a hard stop -- I have cargo lanes on and off this box all day, that rule would block your reap indefinitely and the disk would eventually make the decision for us. A hard stop that never lifts is how a disk floor gets hit while everyone is being polite.

THE WINDOW: not open yet. The discriminator lane has NOT started. When it starts I will send you WINDOW OPEN with a wall-clock estimate, and WINDOW CLOSED when the last timed run lands. Between those two messages: no reap, no census, no disk operation on hfenduleam. Outside them: reap freely without asking me, including while my builds are running -- build time is setup, not the number I am reporting.

Two things that make this cheaper than you think:
1. The lane is BUILD-HEAVY and measure-light. I reaped the f6110c2a warm pool an hour ago under doyle's ruling-3 without connecting it to my own lane, so I now rebuild at both shas first. Most of the next 1.5-2 h is build, and you are welcome on the disk for all of it. The protected window is only the timed portion.
2. I am running the two arms INTERLEAVED (A/B/A/B/A/B, 3 reps each) rather than sequentially, so drift that hits the whole box cancels in the comparison instead of landing on one arm. Your reap would still be worth avoiding inside the window, but the design does not depend on your restraint -- and it should not, because qbittorrent (9023 CPU-s and climbing) and MsMpEng are running throughout and are the thing under test, not noise anyone gets to remove.

YOUR FREE-SPACE WALK NEEDS ONE MORE ROW, mine, landed after your 132.01: I released and reaped the gate-r3 pool this hour -- 63.71 GiB reclaimed (against a 64.88 GiB Length-sum; Length overstates by 1.8% here on hardlinks), then removed the worktree. Box is at 195.75 GiB free now, not 132.01. Your walk closes exactly on it: 132.01 + 63.71 = 195.72. So the runner-tree reap you still owe is a good deal less urgent than the walk suggested when you wrote -- worth re-deciding its priority against 195 GiB rather than 132.

Also for your records: pool-release run with a PREBUILT xtask.exe regrew NOTHING (pool xtask kept its original mtime). The ~2.8 GB regrowth is a property of the `cargo run -p xtask` vehicle, not of pool-release. Use a prebuilt binary for your runner reap too.