[Bug]: A thread refused with DEVICE_IN_USE can still tap on the device #31303

Before submitting

• I searched existing issues and did not find a duplicate.
• I included enough detail to reproduce or investigate the problem.

Area

apps/server

Steps to reproduce

1. Thread A: device_open an Android emulator, then <launcher> open com.android.settings.
2. Thread B: device_open the same emulator, then <launcher> open com.android.settings. This fails with DEVICE_IN_USE.
3. Thread B: <launcher> snapshot -i, then <launcher> press <x> <y>.

Expected behavior

Thread B's commands are refused while thread A holds the device.

Actual behavior

Only open is refused. B's snapshot returns A's screen, and B's press taps A's app:

$ B open com.android.settings   -> Error (DEVICE_IN_USE)                exit 1
$ B snapshot -i                 -> A's Settings screen                  exit 0
$ A session list                -> A's session and B's, same emulator
$ B press 400 860               -> Tapped (400, 860)                    exit 0

This happened for real with several threads sharing one emulator: a thread refused at open went on to tap and swipe through another thread's app.

Cause

• T3's device_open launcher adds --platform and --serial to every command.
• agent-device 0.21.31 runs a command for a session that never opened if it has those flags. A snapshot run that way even creates the missing session. Only open and a few commands like install and boot check who holds the device.

This is different from #17470. There, a device stays held after a thread is done. Here, a held device doesn't stop another thread.

Impact

Major degradation or frequent failure

Version or commit

main at 67eebac, agent-device 0.21.31

Environment

Linux, local Android emulator (API 35)

Screenshots, recordings, or supporting files

Before B's press	After B's press

Workaround

None. The agent has to stop by itself after open is refused.