ConvAgent: send agent audio multicast Unreliable + add size debug log

- MulticastReceiveAgentAudio: Reliable -> Unreliable. Realtime audio: a lost or
  oversized packet is dropped (minor glitch) instead of backing up the reliable
  buffer and dropping the client connection.
- Raw-PCM fallback chunk size 32000 -> 4000 bytes so an unreliable RPC is not
  auto-promoted to reliable when fragmented into many partial bunches (which
  would reintroduce the overflow).
- Add net-audio size log gated behind ps.ai.ConvAgent.Debug.ElevenLabs; fires on
  Authority even in solo PIE: "[NET-SRV] Opus audio chunk: N bytes (raw M -> Xx)".

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Unreal/PS_AI_Agent/Config/DefaultEngine.ini

@@ -166,6 +166,14 @@ DefaultPlatformService=Null
 [OnlineSubsystemNull]
 bEnabled=true
 
+[Voice]
+; Enable the Voice module so FVoiceModule::CreateVoiceEncoder() returns a valid
+; Opus encoder/decoder. The engine default is bEnabled=false, which leaves the
+; encoder NULL and makes networked agent audio fall back to raw PCM in large
+; reliable multicast RPCs — these overflow the reliable buffer and drop VR
+; client connections the moment the avatar speaks. With Opus, chunks are ~1-4KB.
+bEnabled=true
+
 [/Script/AndroidFileServerEditor.AndroidFileServerRuntimeSettings]
 bEnablePlugin=True
 bAllowNetworkConnection=True

Unreal/PS_AI_Agent/Plugins/PS_AI_ConvAgent/Source/PS_AI_ConvAgent/Private/PS_AI_ConvAgent_ElevenLabsComponent.cpp

@@ -1224,6 +1224,11 @@ void UPS_AI_ConvAgent_ElevenLabsComponent::HandleAudioReceived(const TArray<uint
 	// Network: broadcast audio to all clients.
 	if (GetOwnerRole() == ROLE_Authority)
 	{
+		// Net-audio size debug: toggle at runtime with
+		//   ps.ai.ConvAgent.Debug.ElevenLabs 1   (or set bDebug on the component).
+		const int32 NetDbgCVar = CVarDebugElevenLabs.GetValueOnGameThread();
+		const bool bNetAudioDebug = (NetDbgCVar >= 0) ? (NetDbgCVar > 0) : bDebug;
+
 		if (OpusEncoder.IsValid())
 		{
 			// Opus path: compress then send.
@@ -1235,14 +1240,28 @@ void UPS_AI_ConvAgent_ElevenLabsComponent::HandleAudioReceived(const TArray<uint
 			{
 				TArray<uint8> CompressedData;
 				CompressedData.Append(OpusWorkBuffer.GetData(), CompressedSize);
+
+				if (bNetAudioDebug)
+				{
+					const float Ratio = (CompressedSize > 0)
+						? static_cast<float>(PCMData.Num()) / static_cast<float>(CompressedSize)
+						: 0.0f;
+					UE_LOG(LogPS_AI_ConvAgent_ElevenLabs, Log,
+						TEXT("[NET-SRV] Opus audio chunk: %u bytes sent (raw %d → %.1fx compression)."),
+						CompressedSize, PCMData.Num(), Ratio);
+				}
+
 				MulticastReceiveAgentAudio(CompressedData);
 			}
 		}
 		else
 		{
 			// Fallback: send raw PCM (no compression). ~32 KB/s at 16kHz 16-bit mono.
-			// Fine for LAN; revisit with proper Opus if internet play is needed.
+			// Only hit if Opus init failed. Chunk small so the Unreliable RPC is
-			// UE5 limits replicated TArrays to 65535 elements, so we must chunk.
+			// NOT auto-promoted to reliable when fragmented: UE re-sends an
+			// unreliable bunch reliably once it splits into more than ~8 partial
+			// bunches, which would reintroduce the reliable-buffer overflow.
+			// ~4 KB ≈ 4 bunches → stays unreliable.
 			static bool bWarnedOnce = false;
 			if (!bWarnedOnce)
 			{
@@ -1251,13 +1270,21 @@ void UPS_AI_ConvAgent_ElevenLabsComponent::HandleAudioReceived(const TArray<uint
 					TEXT("[NET-SRV] Opus encoder unavailable — sending raw PCM in chunks (no compression)."));
 			}
 
-			static constexpr int32 MaxChunkBytes = 32000; // 1s of 16kHz 16-bit mono, well under 65535 limit
+			static constexpr int32 MaxChunkBytes = 4000; // small enough to stay unreliable (avoid partial-bunch reliable promotion)
 			int32 Offset = 0;
 			while (Offset < PCMData.Num())
 			{
 				const int32 ChunkSize = FMath::Min(MaxChunkBytes, PCMData.Num() - Offset);
 				TArray<uint8> Chunk;
 				Chunk.Append(PCMData.GetData() + Offset, ChunkSize);
+
+				if (bNetAudioDebug)
+				{
+					UE_LOG(LogPS_AI_ConvAgent_ElevenLabs, Warning,
+						TEXT("[NET-SRV] RAW PCM chunk: %d bytes sent (NO compression — Opus disabled)."),
+						ChunkSize);
+				}
+
 				MulticastReceiveAgentAudio(Chunk);
 				Offset += ChunkSize;
 			}

Unreal/PS_AI_Agent/Plugins/PS_AI_ConvAgent/Source/PS_AI_ConvAgent/Public/PS_AI_ConvAgent_ElevenLabsComponent.h

@@ -484,8 +484,12 @@ public:
 	UFUNCTION(Server, Reliable)
 	void ServerRequestInterrupt();
 
-	/** Broadcast agent audio to all clients (Opus-compressed or raw PCM fallback). */
+	/** Broadcast agent audio to all clients (Opus-compressed or raw PCM fallback).
-	UFUNCTION(NetMulticast, Reliable)
+	 *  Unreliable: realtime audio — a lost/oversized packet is dropped (minor
+	 *  glitch) rather than backing up the reliable buffer and dropping the
+	 *  connection. Keep each call small (Opus ~1-4KB) so it isn't auto-promoted
+	 *  to reliable when fragmented into partial bunches. */
+	UFUNCTION(NetMulticast, Unreliable)
 	void MulticastReceiveAgentAudio(const TArray<uint8>& AudioData);
 
 	/** Notify all clients that the agent started speaking (first audio chunk). */