[ben-dz]

Summary of Changes

• This PR makes AssignDevicesToClients pad a host's shorter device list with the last device in that list that can accept users (Ready()).
• Before, it padded with the last device, even when that device had max_users=0.
• The all-devices QA test then connected the host to that device again in every padded batch.
• A host with no device that can accept users still pads with its last device.
• In the mainnet-beta run at 20:00 UTC on 2026-11-14, aws-sin-mn-qa2 had dz-sg1-sw01 (max_users=0) last in its list and timed out on it 11 times.
• Each status wait timed out after about 85 seconds, so batches 6 onward took 130 to 155 seconds instead of 50 to 65.
• That run took about 37 minutes, against the usual 22 to 29.
• DetermineClientsToConnect keeps a host connected when its device is the same as in the previous batch and its status is up.
• So padded batches do not connect the host again while its status stays up.
• The exception is a list that ends with a device that cannot accept users, where the first padded batch connects once to the ready device.
• The ready device now gets the retests of the padded batches, and it passes if any one of its tests succeeds.

Testing Verification

• A new TestAssignDevicesToClients case gives a host the list dev1, dev2, drained, and checks that both padded batches use dev2.
• This case fails on main, where both padded batches use drained.
• A second case gives a host only devices with max_users=0, and checks that the host still pads with its last device.
• This change did not run against the QA hosts.
• The effect on run time shows only after merge, in the next mainnet-beta all-devices runs.

[Copilot]

🟢 Approval recommended

No active review issues remain for the change to prefer ready devices when padding host assignments.

No open issues 🎉

What changed in this PR

This PR reduces repeated connection timeouts in the all-devices QA test by changing how hosts pad shorter device lists.

Changes:

• AssignDevicesToClients now pads with the last ready device in the host’s assigned list.
• Hosts with no ready device still pad with their last assigned device.
• Two regression tests cover ready-device selection and the fallback when no device is ready.

File	Description
e2e/​internal/​qa/​device_assignment.go	Selects the last ready device for padding while preserving the fallback.
e2e/​internal/​qa/​device_assignment_test.go	Adds regression cases for both padding paths.
CHANGELOG.md	Documents the padding change and the QA timeout context.

_{Review effort: Balanced}