Pipes are not working for nested generators

Description
Sending data via ProcessorInstance.Pipe in a nested generator throws an exception.

Initial setup

Download, unzip and open the attached Unity project sap-message-pipe-repro.

Reproduction steps

1. Open the scene SampleScene
2. Enter play mode

Expected behaviour

The editor should run without per-frame exceptions / console spam.

Actual behavior

An exception is thrown every frame, spamming the console.

Reproducible with versions

6000.3.6f1, 6000.4.0b6, 6000.5.0a7

Not reproducible with versions

Not relevant for versions pre 6.3 as the feature did not exist in versions prior to that.

Can’t test with versions

Not relevant for versions pre 6.3.

Tested on (OS): 

macOS 26.2

Logs and Links

Stack trace:

InvalidOperationException: DualThreadHandle is not valid, cannot get available data.
UnityEngine.Audio.ProcessorInstance+Pipe.GetAvailableData[TAudioContext] (TAudioContext context) (at /opt/UnitySrc/unity1/Modules/Audio/Public/ScriptableProcessors/ScriptBindings/ScriptableProcessor.bindings.cs:262)
SynthAsset+Realtime.Process (UnityEngine.Audio.RealtimeContext& context, UnityEngine.Audio.ProcessorInstance+Pipe pipe, UnityEngine.Audio.ChannelBuffer buffer, UnityEngine.Audio.GeneratorInstance+Arguments args) (at Assets/Scripts/Child.cs:23)
SynthAsset+Realtime.UnityEngine.Audio.GeneratorInstance.IRealtime.Process (UnityEngine.Audio.RealtimeContext& context, UnityEngine.Audio.ProcessorInstance+Pipe pipe, UnityEngine.Audio.ChannelBuffer buffer, UnityEngine.Audio.GeneratorInstance+Arguments args) <0x3c59fc468 + 0x000ff> in <40f815355a454e4a92d147089da3a8d9>:0
UnityEngine.Audio.IGeneratorProcessorExtensions+JobStruct`1[TUserProcessor].Execute (UnityEngine.Audio.IGeneratorProcessorExtensions+JobStruct`1+Storage[TUserProcessor]& storage, System.IntPtr additionalPtr, System.IntPtr additionalPtr2, Unity.Jobs.LowLevel.Unsafe.JobRanges& ranges, System.Int32 jobIndex) (at /opt/UnitySrc/unity1/Modules/Audio/Public/ScriptableProcessors/ScriptBindings/ScriptableGenerator.bindings.cs:578)
UnityEngine.Audio.ProcessorHeader:wrapper_native_indirect_0x9dee41fb8(IntPtr&, ProcessorHeader*, ProcessorFunction, Void*)
UnityEngine.Audio.ProcessorHeader:InvokeProcessor(ProcessorFunction, Void*) (at /opt/UnitySrc/unity1/Modules/Audio/Public/ScriptableProcessors/ScriptBindings/ScriptableProcessor.bindings.cs:627)
UnityEngine.Audio.RealtimeContext:Process(GeneratorInstance, ChannelBuffer, Arguments) (at /opt/UnitySrc/unity1/Modules/Audio/Public/ScriptableProcessors/ScriptBindings/RealtimeContext.cs:67)
Realtime:Process(RealtimeContext&, Pipe, ChannelBuffer, Arguments) (at Assets/Scripts/Parent.cs:26)
Realtime:UnityEngine.Audio.GeneratorInstance.IRealtime.Process(RealtimeContext&, Pipe, ChannelBuffer, Arguments)
UnityEngine.Audio.JobStruct`1:Execute(Storage&, IntPtr, IntPtr, JobRanges&, Int32) (at /opt/UnitySrc/unity1/Modules/Audio/Public/ScriptableProcessors/ScriptBindings/ScriptableGenerator.bindings.cs:578)