Fix AudioSwitchHandler leaving audio active when stopped during start

[davidliu]

Problem

start() builds the AudioSwitch in a job on the AudioSwitchHandlerThread. If stop() is called while that job is already running, stop() can't cancel it, and it finds no audioSwitch to tear down yet. The job then stores the switch and calls start()/activate(), leaving audio focus, audio mode and routing active with nothing to stop them.

Fix

start() records the handler it posted the creation job to. Before storing the switch, the job checks under the handler's lock (the same one start()/stop() use) that handler is still that one.

• stop() got there first: handler has changed, so the job drops the switch before starting it. That's safe because the audioswitch constructors register nothing; scanning, focus and routing only begin in start()/activate().
• The job got there first: the switch is stored, so a following stop() finds it and posts its teardown behind the running job.

This follows up on #967, which made stop() clear audioSwitch straight away.

Testing

• :livekit-android-sdk:compileDebugKotlin, detektRelease, spotlessCheck

🤖 Generated with Claude Code

[changeset-bot]

🦋 Changeset detected

Latest commit: 545cace

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
client-sdk-android	Patch

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[devin-ai-integration]

Devin Review found 1 potential issue.

[devin-ai-integration]

🔴 Repeated starts leave audio routing active

If start() runs again during switch construction, both jobs pass the startHandler check and publish separate switches. The second replaces audioSwitch, so stop() cannot stop the first; audio routing remains active.

Learn more

A start job is queued on the handler thread, but the switch reference stays null until construction finishes. If another start() occurs while construction is already running, start observes null and queues a second job on the same handler. Both jobs pass the handler identity check. The second job replaces the first switch reference; stop only retains and stops the latest switch.

Example: Thread A begins constructing switch A. A second start() queues switch B before A publishes. Both publish and activate. A later stop() stops B; A stays active.

Recommended fix: Track a start generation or pending-start state, and reject jobs that no longer own the current generation. Ensure a running job is stopped if a newer start supersedes it; add a test that pauses construction across a repeated start().

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[github-actions]

Diffuse output:

OLD: diffuse-source-file
NEW: livekit-android-sdk-release.aar

 AAR      │ old      │ new      │ diff   
──────────┼──────────┼──────────┼────────
      jar │    3 MiB │    3 MiB │ +188 B 
 manifest │  1.5 KiB │  1.5 KiB │    0 B 
 lint-jar │ 12.7 KiB │ 12.7 KiB │    0 B 
    other │  2.4 KiB │  2.4 KiB │    0 B 
──────────┼──────────┼──────────┼────────
    total │    3 MiB │    3 MiB │ +188 B 

 JAR     │ old   │ new   │ diff      
─────────┼───────┼───────┼───────────
 classes │  1706 │  1706 │ 0 (+0 -0) 
 methods │ 21983 │ 21983 │ 0 (+3 -3) 
  fields │  5703 │  5703 │ 0 (+0 -0)

AAR

 size  │ diff   │ path          
───────┼────────┼───────────────
 3 MiB │ +188 B │ ∆ classes.jar 
───────┼────────┼───────────────
 3 MiB │ +188 B │ (total)

JAR

METHODS:

   old   │ new   │ diff      
  ───────┼───────┼───────────
   21983 │ 21983 │ 0 (+3 -3) 
  
  + io.livekit.android.audio.AudioSwitchHandler selectDevice_lambda_6(AudioSwitchHandler, AudioDevice)
  + io.livekit.android.audio.AudioSwitchHandler start_lambda_4(AudioSwitchHandler, Handler)
  + io.livekit.android.audio.AudioSwitchHandler stop_lambda_5(AbstractAudioSwitch)
  
  - io.livekit.android.audio.AudioSwitchHandler selectDevice_lambda_5(AudioSwitchHandler, AudioDevice)
  - io.livekit.android.audio.AudioSwitchHandler start_lambda_3(AudioSwitchHandler)
  - io.livekit.android.audio.AudioSwitchHandler stop_lambda_4(AbstractAudioSwitch)