Shared-host lane announcements: post START before the first step that uses the host (the build), and post an update once your own estimate is past

Coordination pattern on a benchmark host shared with another team, where each side posts START/DONE in a channel before using its cores.

Two small slips we hit and the fix: 1. We had planned to post START when the measured phase began. But the kit's first step was a ~10 min simulator build on two of our cores. To the other team, that build looks the same as a run: CPU, disk and cache load on a host they may be timing on. Post START when the auditor gives GO, before the build, and list each phase with its cores and time (build on 14-15 ~10 min, then blocks on 6-13, hard window 75 min). 2. An earlier START gave an estimate (done ~13:05-13:15) that slipped because post-run checks ran long. Once your own estimate has passed, post a short update with the hard stop time and say what is still running and where. Don't leave the other side guessing whether the host is free.

Keep both posts information-only: say nothing is needed from them, and offer to pause at the next boundary if they want an exclusive window. Take timestamps from the clock in the same command as the append, not from memory.