LiveKitComponents - Task-isolated value of type '() async -> ()' passed as strongly transferred parameter in AudioProcessor.render()

[svolla-aura]

Description

Hi LiveKit team,

I’m evaluating the agent-starter-swift example on Xcode 16 (Swift 6 toolchain) and ran into a Swift concurrency warning related to the AudioProcessor class (which is part of LiveKitComponents).

---

Error

Task-isolated value of type '() async -> ()' passed as a strongly transferred parameter; later accesses could race

components-swift/Sources/LiveKitComponents/Audio/AudioProcessor.swift

Line 51 in f756f36

Task {

File: Sources/LiveKitComponents/Audio/AudioProcessor.swift
Line: ~51
Function: public nonisolated func render(pcmBuffer: AVAudioPCMBuffer)

---

Steps to Reproduce

1. Clone livekit-examples/agent-starter-swift
2. Open in Xcode 16.0 (Swift 6)
3. Build or run the iOS target (e.g., VoiceAgent)
4. Observe the compiler warning in AudioProcessor.swift

---

Snippet

public nonisolated func render(pcmBuffer: AVAudioPCMBuffer) {
    Task {
        let newBands = await processor.process(pcmBuffer: pcmBuffer)
        guard var newBands else { return }

        if isCentered {
            newBands.sort(by: >)
            newBands = Self.centerBands(newBands)
        }

        await MainActor.run { [newBands] in
            bands = zip(bands, newBands).map { old, new in
                Self.smoothTransition(from: old, to: new, factor: smoothingFactor)
            }
        }
    }
}

---

Possible Fix / Workaround

Using explicit actor isolation or Task.detached eliminates the warning, but semantics might differ:

Task { @MainActor in
    // ...
}

or

await MainActor.run { ... }

[svolla-aura]

@hiroshihorie @pblazej @davidzhao @lukaszb

Hi Team,

Could you please confirm the correct concurrency isolation pattern here under Swift 6?
I can submit a PR once confirmed.

[svolla-aura]

Solution:

 public nonisolated func render(pcmBuffer: AVAudioPCMBuffer) {
        Task { @MainActor [weak self] in
            guard let self else { return }
            
            let newBandsOpt = await self.processor.process(pcmBuffer: pcmBuffer)
            guard var newBands = newBandsOpt else { return }
            
            // If centering is enabled, rearrange the normalized bands
            if self.isCentered {
                newBands.sort(by: >)
                newBands = Self.centerBands(newBands)
            }
            
            self.bands = zip(self.bands, newBands).map { old, new in
                Self.smoothTransition(from: old, to: new, factor: smoothingFactor)
            }
        }
    }

[pblazej]

@svolla-aura the intention here is to perform audio processing outside main thread. This issue hasn't been reproduced before and looks like a false positive. I'd suggest either:

• updating to Xcode 26
• importing LiveKitComponents with @preconcurrency (as a temporary workaround)

EDIT: Double-checked Xcode 16.4 and the project builds completely fine 👍

[pblazej]

Closing as non-reproducible