Unexpected room reconnect when publishing video with custom simulcast layers

[jankosecki]

Select which package(s) are affected

@livekit/components-react

Describe the bug

When videoSimulcastLayers or screenShareSimulcastLayers are passed in options to <LiveKitRoom /> (or useLiveKitRoom), publishing a video track can trigger a full room teardown and reconnect.

The cause is a combination of two things:

1. useLiveKitRoom recreates the Room instance whenever JSON.stringify(options) changes between renders.
2. The livekit-client SDK's internal sortPresets function sorts simulcast layer arrays in place when a track is published, mutating the original options object.

After the first publish, the simulcast layers array inside options has been reordered. On the next render, JSON.stringify(options) produces a different string, the effect fires, a new Room is created, and the old one is disconnected.

Reproduction

Pass videoSimulcastLayers in an order that isn't already sorted by maxBitrate ascending, then publish a camera track. You'll see the room disconnect and reconnect.

Logs

System Info

System:
    OS: macOS 26.5.1
    CPU: (10) arm64 Apple M4
    Memory: 116.52 MB / 16.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 24.16.0 - /Users/jk/.nvm/versions/node/v24.16.0/bin/node
    Yarn: 1.22.22 - /opt/homebrew/bin/yarn
    npm: 11.13.0 - /Users/jk/.nvm/versions/node/v24.16.0/bin/npm
    pnpm: 10.28.1 - /opt/homebrew/bin/pnpm
  Browsers:
    Chrome: 149.0.7827.115
    Firefox: 152.0
    Safari: 26.5
  npmPackages:
    @livekit/components-core: ^0.12.13 => 0.12.13 
    @livekit/components-react: ^2.9.21 => 2.9.21 
    @livekit/components-styles: ^1.2.0 => 1.2.0 
    livekit-client: ^2.19.1 => 2.19.1

Severity

annoyance

Additional Information

No response

[1egoman]

Hi @jankosecki, thanks for the report! I think this is actually a bug in client-sdk-js - I've opened up a pull request over there: livekit/client-sdk-js#1979

[jankosecki]

Amazing! Thanks for addressing it so quickly. For time being we just made sure that our simulcast array is defined in the right order 😄