Fix Ask AI conversation ID handling

src/api/Elastic.Documentation.Api.Core/AskAi/AskAiUsecase.cs

@@ -9,7 +9,7 @@
 namespace Elastic.Documentation.Api.Core.AskAi;
 
 public class AskAiUsecase(
-	IAskAiGateway<Stream> askAiGateway,
+	IAskAiGateway askAiGateway,
 	IStreamTransformer streamTransformer,
 	ILogger<AskAiUsecase> logger)
 {
@@ -24,6 +24,7 @@ public async Task<Stream> AskAi(AskAiRequest askAiRequest, Cancel ctx)
 		_ = activity?.SetTag("gen_ai.agent.id", streamTransformer.AgentId); // docs-agent or docs_assistant
 		if (askAiRequest.ConversationId is not null)
 			_ = activity?.SetTag("gen_ai.conversation.id", askAiRequest.ConversationId.ToString());
+
 		var inputMessages = new[]
 		{
 			new InputMessage("user", [new MessagePart("text", askAiRequest.Message)])
@@ -33,9 +34,22 @@ public async Task<Stream> AskAi(AskAiRequest askAiRequest, Cancel ctx)
 		var sanitizedMessage = askAiRequest.Message?.Replace("\r", "").Replace("\n", "");
 		logger.LogInformation("AskAI input message: <{ask_ai.input.message}>", sanitizedMessage);
 		logger.LogInformation("Streaming AskAI response");
-		var rawStream = await askAiGateway.AskAi(askAiRequest, ctx);
-		// The stream transformer will handle disposing the activity when streaming completes
-		var transformedStream = await streamTransformer.TransformAsync(rawStream, askAiRequest.ConversationId?.ToString(), activity, ctx);
+
+		// Gateway handles conversation ID generation if needed
+		var response = await askAiGateway.AskAi(askAiRequest, ctx);
+
+		// Use generated ID if available, otherwise use the original request ID
+		var conversationId = response.GeneratedConversationId ?? askAiRequest.ConversationId;
+		if (conversationId is not null)
+			_ = activity?.SetTag("gen_ai.conversation.id", conversationId.ToString());
+
+		// The stream transformer takes ownership of the activity and disposes it when streaming completes.
+		// This is necessary because streaming happens asynchronously after this method returns.
+		var transformedStream = await streamTransformer.TransformAsync(
+			response.Stream,
+			response.GeneratedConversationId,
+			activity,
+			ctx);
 		return transformedStream;
 	}
 }

src/api/Elastic.Documentation.Api.Core/AskAi/IAskAiGateway.cs

@@ -4,7 +4,18 @@
 
 namespace Elastic.Documentation.Api.Core.AskAi;
 
-public interface IAskAiGateway<T>
+/// <summary>
+/// Response from an AI gateway containing the stream and conversation metadata
+/// </summary>
+/// <param name="Stream">The SSE response stream</param>
+/// <param name="GeneratedConversationId">
+/// Non-null ONLY if the gateway generated a new conversation ID for this request.
+/// When set, the transformer should emit a ConversationStart event with this ID.
+/// Null means either: (1) user provided an ID (continuing conversation), or (2) gateway doesn't generate IDs (e.g., Agent Builder).
+/// </param>
+public record AskAiGatewayResponse(Stream Stream, Guid? GeneratedConversationId);
+
+public interface IAskAiGateway
 {
-	Task<T> AskAi(AskAiRequest askAiRequest, Cancel ctx = default);
+	Task<AskAiGatewayResponse> AskAi(AskAiRequest askAiRequest, Cancel ctx = default);
 }

src/api/Elastic.Documentation.Api.Core/AskAi/IStreamTransformer.cs

@@ -23,9 +23,12 @@ public interface IStreamTransformer
 	/// Transforms a raw SSE stream into a stream of AskAiEvent objects
 	/// </summary>
 	/// <param name="rawStream">Raw SSE stream from gateway (Agent Builder, LLM Gateway, etc.)</param>
-	/// <param name="conversationId">Thread/conversation ID (if known)</param>
+	/// <param name="generatedConversationId">
+	/// Non-null if the gateway generated a new conversation ID (LLM Gateway only).
+	/// When set, transformer should emit ConversationStart event with this ID.
+	/// </param>
 	/// <param name="parentActivity">Parent activity to track the streaming operation (will be disposed when stream completes)</param>
 	/// <param name="cancellationToken">Cancellation token</param>
 	/// <returns>Stream containing SSE-formatted AskAiEvent objects</returns>
-	Task<Stream> TransformAsync(Stream rawStream, string? conversationId, System.Diagnostics.Activity? parentActivity, CancellationToken cancellationToken = default);
+	Task<Stream> TransformAsync(Stream rawStream, Guid? generatedConversationId, System.Diagnostics.Activity? parentActivity, CancellationToken cancellationToken = default);
 }

src/api/Elastic.Documentation.Api.Infrastructure/Adapters/AskAi/AgentBuilderAskAiGateway.cs

@@ -12,7 +12,7 @@
 
 namespace Elastic.Documentation.Api.Infrastructure.Adapters.AskAi;
 
-public class AgentBuilderAskAiGateway(HttpClient httpClient, KibanaOptions kibanaOptions, ILogger<AgentBuilderAskAiGateway> logger) : IAskAiGateway<Stream>
+public class AgentBuilderAskAiGateway(HttpClient httpClient, KibanaOptions kibanaOptions, ILogger<AgentBuilderAskAiGateway> logger) : IAskAiGateway
 {
 	/// <summary>
 	/// Model name used by Agent Builder (from AgentId)
@@ -23,8 +23,10 @@ public class AgentBuilderAskAiGateway(HttpClient httpClient, KibanaOptions kiban
 	/// Provider name for tracing
 	/// </summary>
 	public const string ProviderName = "agent-builder";
-	public async Task<Stream> AskAi(AskAiRequest askAiRequest, Cancel ctx = default)
+	public async Task<AskAiGatewayResponse> AskAi(AskAiRequest askAiRequest, Cancel ctx = default)
 	{
+		// Agent Builder returns the conversation ID in the stream via conversation_id_set event
+		// We don't generate IDs - Agent Builder handles that in the stream
 		var agentBuilderPayload = new AgentBuilderPayload(
 			askAiRequest.Message,
 			"docs-agent",
@@ -55,7 +57,9 @@ public async Task<Stream> AskAi(AskAiRequest askAiRequest, Cancel ctx = default)
 		logger.LogInformation("Response Content-Length: {ContentLength}", response.Content.Headers.ContentLength?.ToString(CultureInfo.InvariantCulture));
 
 		// Agent Builder already returns SSE format, just return the stream directly
-		return await response.Content.ReadAsStreamAsync(ctx);
+		// The conversation ID will be extracted from the stream by the transformer
+		var stream = await response.Content.ReadAsStreamAsync(ctx);
+		return new AskAiGatewayResponse(stream, GeneratedConversationId: null);
 	}
 }
 

src/api/Elastic.Documentation.Api.Infrastructure/Adapters/AskAi/AskAiGatewayFactory.cs

@@ -14,13 +14,13 @@ namespace Elastic.Documentation.Api.Infrastructure.Adapters.AskAi;
 public class AskAiGatewayFactory(
 	IServiceProvider serviceProvider,
 	AskAiProviderResolver providerResolver,
-	ILogger<AskAiGatewayFactory> logger) : IAskAiGateway<Stream>
+	ILogger<AskAiGatewayFactory> logger) : IAskAiGateway
 {
-	public async Task<Stream> AskAi(AskAiRequest askAiRequest, Cancel ctx = default)
+	public async Task<AskAiGatewayResponse> AskAi(AskAiRequest askAiRequest, Cancel ctx = default)
 	{
 		var provider = providerResolver.ResolveProvider();
 
-		IAskAiGateway<Stream> gateway = provider switch
+		IAskAiGateway gateway = provider switch
 		{
 			"LlmGateway" => serviceProvider.GetRequiredService<LlmGatewayAskAiGateway>(),
 			"AgentBuilder" => serviceProvider.GetRequiredService<AgentBuilderAskAiGateway>(),

src/api/Elastic.Documentation.Api.Infrastructure/Adapters/AskAi/LlmGatewayAskAiGateway.cs

@@ -10,7 +10,7 @@
 
 namespace Elastic.Documentation.Api.Infrastructure.Adapters.AskAi;
 
-public class LlmGatewayAskAiGateway(HttpClient httpClient, IGcpIdTokenProvider tokenProvider, LlmGatewayOptions options) : IAskAiGateway<Stream>
+public class LlmGatewayAskAiGateway(HttpClient httpClient, IGcpIdTokenProvider tokenProvider, LlmGatewayOptions options) : IAskAiGateway
 {
 	/// <summary>
 	/// Model name used by LLM Gateway (from PlatformContext.UseCase)
@@ -21,9 +21,13 @@ public class LlmGatewayAskAiGateway(HttpClient httpClient, IGcpIdTokenProvider t
 	/// Provider name for tracing
 	/// </summary>
 	public const string ProviderName = "llm-gateway";
-	public async Task<Stream> AskAi(AskAiRequest askAiRequest, Cancel ctx = default)
+	public async Task<AskAiGatewayResponse> AskAi(AskAiRequest askAiRequest, Cancel ctx = default)
 	{
-		var llmGatewayRequest = LlmGatewayRequest.CreateFromRequest(askAiRequest);
+		// LLM Gateway requires a ThreadId - generate one if not provided
+		var generatedId = askAiRequest.ConversationId is null ? Guid.NewGuid() : (Guid?)null;
+		var threadId = askAiRequest.ConversationId ?? generatedId!.Value;
+
+		var llmGatewayRequest = LlmGatewayRequest.CreateFromRequest(askAiRequest, threadId);
 		var requestBody = JsonSerializer.Serialize(llmGatewayRequest, LlmGatewayContext.Default.LlmGatewayRequest);
 		using var request = new HttpRequestMessage(HttpMethod.Post, options.FunctionUrl);
 		request.Content = new StringContent(requestBody, Encoding.UTF8, "application/json");
@@ -46,7 +50,8 @@ public async Task<Stream> AskAi(AskAiRequest askAiRequest, Cancel ctx = default)
 
 		// Return the response stream directly - this enables true streaming
 		// The stream will be consumed as data arrives from the LLM Gateway
-		return await response.Content.ReadAsStreamAsync(ctx);
+		var stream = await response.Content.ReadAsStreamAsync(ctx);
+		return new AskAiGatewayResponse(stream, generatedId);
 	}
 }
 
@@ -57,7 +62,7 @@ public record LlmGatewayRequest(
 	string ThreadId
 )
 {
-	public static LlmGatewayRequest CreateFromRequest(AskAiRequest request) =>
+	public static LlmGatewayRequest CreateFromRequest(AskAiRequest request, Guid conversationId) =>
 		new(
 			UserContext: new UserContext("elastic-docs-v3@invalid"),
 			PlatformContext: new PlatformContext("docs_site", "docs_assistant", []),
@@ -66,7 +71,7 @@ public static LlmGatewayRequest CreateFromRequest(AskAiRequest request) =>
 				// new ChatInput("user", AskAiRequest.SystemPrompt),
 				new ChatInput("user", request.Message)
 			],
-			ThreadId: request.ConversationId?.ToString() ?? Guid.NewGuid().ToString()
+			ThreadId: conversationId.ToString()
 		);
 }
 

src/api/Elastic.Documentation.Api.Infrastructure/Adapters/AskAi/LlmGatewayStreamTransformer.cs

@@ -19,33 +19,33 @@ public class LlmGatewayStreamTransformer(ILogger<LlmGatewayStreamTransformer> lo
 	protected override string GetAgentProvider() => LlmGatewayAskAiGateway.ProviderName;
 
 	/// <summary>
-	/// Override to emit ConversationStart event when conversationId is null (new conversation)
+	/// Override to emit ConversationStart event for new conversations.
+	/// LLM Gateway doesn't return a conversation ID, so we emit one to match Agent Builder behavior.
+	/// The generatedConversationId is the ID generated by the gateway and used as ThreadId.
 	/// </summary>
-	protected override async Task ProcessStreamAsync(PipeReader reader, PipeWriter writer, string? conversationId, Activity? parentActivity, CancellationToken cancellationToken)
+	protected override async Task ProcessStreamAsync(PipeReader reader, PipeWriter writer, Guid? generatedConversationId, Activity? parentActivity, CancellationToken cancellationToken)
 	{
-		// If conversationId is null, generate a new one and emit ConversationStart event
-		// This matches the ThreadId format used in LlmGatewayAskAiGateway
-		var actualConversationId = conversationId;
-		if (conversationId == null)
+		// Emit ConversationStart event only if a new conversation ID was generated
+		if (generatedConversationId is not null)
 		{
-			actualConversationId = Guid.NewGuid().ToString();
+			var conversationId = generatedConversationId.Value.ToString();
 			var timestamp = DateTimeOffset.UtcNow.ToUnixTimeMilliseconds();
 			var conversationStartEvent = new AskAiEvent.ConversationStart(
 				Id: Guid.NewGuid().ToString(),
 				Timestamp: timestamp,
-				ConversationId: actualConversationId
+				ConversationId: conversationId
 			);
 
 			// Set activity tags for the new conversation
-			_ = parentActivity?.SetTag("gen_ai.conversation.id", actualConversationId);
-			Logger.LogDebug("LLM Gateway conversation started: {ConversationId}", actualConversationId);
+			_ = parentActivity?.SetTag("gen_ai.conversation.id", conversationId);
+			Logger.LogDebug("LLM Gateway conversation started: {ConversationId}", conversationId);
 
 			// Write the ConversationStart event to the stream
 			await WriteEventAsync(conversationStartEvent, writer, cancellationToken);
 		}
 
-		// Continue with normal stream processing using the actual conversation ID
-		await base.ProcessStreamAsync(reader, writer, actualConversationId, parentActivity, cancellationToken);
+		// Continue with normal stream processing
+		await base.ProcessStreamAsync(reader, writer, generatedConversationId, parentActivity, cancellationToken);
 	}
 	protected override AskAiEvent? TransformJsonEvent(string? eventType, JsonElement json)
 	{

src/api/Elastic.Documentation.Api.Infrastructure/Adapters/AskAi/StreamTransformerBase.cs

@@ -42,7 +42,7 @@ public abstract class StreamTransformerBase(ILogger logger) : IStreamTransformer
 	/// </summary>
 	public string AgentProvider => GetAgentProvider();
 
-	public Task<Stream> TransformAsync(Stream rawStream, string? conversationId, Activity? parentActivity, Cancel cancellationToken = default)
+	public Task<Stream> TransformAsync(Stream rawStream, Guid? generatedConversationId, Activity? parentActivity, Cancel cancellationToken = default)
 	{
 		// Configure pipe for low-latency streaming
 		var pipeOptions = new PipeOptions(
@@ -61,7 +61,7 @@ public Task<Stream> TransformAsync(Stream rawStream, string? conversationId, Act
 		// Note: We intentionally don't await this task as we need to return the stream immediately
 		// The pipe handles synchronization and backpressure between producer and consumer
 		// Pass parent activity - it will be disposed when streaming completes
-		_ = ProcessPipeAsync(reader, pipe.Writer, conversationId, parentActivity, cancellationToken);
+		_ = ProcessPipeAsync(reader, pipe.Writer, generatedConversationId, parentActivity, cancellationToken);
 
 		// Return the read side of the pipe as a stream
 		return Task.FromResult(pipe.Reader.AsStream());
@@ -71,48 +71,42 @@ public Task<Stream> TransformAsync(Stream rawStream, string? conversationId, Act
 	/// Process the pipe reader and write transformed events to the pipe writer.
 	/// This runs concurrently with the consumer reading from the output stream.
 	/// </summary>
-	private async Task ProcessPipeAsync(PipeReader reader, PipeWriter writer, string? conversationId, Activity? parentActivity, CancellationToken cancellationToken)
+	private async Task ProcessPipeAsync(PipeReader reader, PipeWriter writer, Guid? generatedConversationId, Activity? parentActivity, CancellationToken cancellationToken)
 	{
+		using var activityScope = parentActivity;
 		try
 		{
+			await ProcessStreamAsync(reader, writer, generatedConversationId, parentActivity, cancellationToken);
+		}
+		catch (OperationCanceledException ex)
+		{
+			Logger.LogDebug(ex, "Stream processing was cancelled for transformer {TransformerType}", GetType().Name);
+		}
+		catch (Exception ex)
+		{
+			Logger.LogError(ex, "Error transforming stream for transformer {TransformerType}. Stream processing will be terminated.", GetType().Name);
+			_ = parentActivity?.SetTag("error.type", ex.GetType().Name);
 			try
 			{
-				await ProcessStreamAsync(reader, writer, conversationId, parentActivity, cancellationToken);
+				// Complete writer first, then reader - but don't try to complete reader
+				// if the exception came from reading (would cause "read operation pending" error)
+				await writer.CompleteAsync(ex);
 			}
-			catch (OperationCanceledException ex)
+			catch (Exception completeEx)
 			{
-				Logger.LogDebug(ex, "Stream processing was cancelled for transformer {TransformerType}", GetType().Name);
-			}
-			catch (Exception ex)
-			{
-				Logger.LogError(ex, "Error transforming stream for transformer {TransformerType}. Stream processing will be terminated.", GetType().Name);
-				_ = parentActivity?.SetTag("error.type", ex.GetType().Name);
-				try
-				{
-					// Complete writer first, then reader - but don't try to complete reader
-					// if the exception came from reading (would cause "read operation pending" error)
-					await writer.CompleteAsync(ex);
-				}
-				catch (Exception completeEx)
-				{
-					Logger.LogError(completeEx, "Error completing pipe after transformation error for transformer {TransformerType}", GetType().Name);
-				}
-				return;
+				Logger.LogError(completeEx, "Error completing pipe after transformation error for transformer {TransformerType}", GetType().Name);
 			}
+			return;
+		}
 
-			// Normal completion - ensure cleanup happens
-			try
-			{
-				await writer.CompleteAsync();
-			}
-			catch (Exception ex)
-			{
-				Logger.LogError(ex, "Error completing pipe after successful transformation");
-			}
+		// Normal completion - ensure cleanup happens
+		try
+		{
+			await writer.CompleteAsync();
 		}
-		finally
+		catch (Exception ex)
 		{
-			parentActivity?.Dispose();
+			Logger.LogError(ex, "Error completing pipe after successful transformation");
 		}
 	}
 
@@ -122,7 +116,7 @@ private async Task ProcessPipeAsync(PipeReader reader, PipeWriter writer, string
 	/// Default implementation parses SSE events and JSON, then calls TransformJsonEvent.
 	/// </summary>
 	/// <returns>Stream processing result with metrics and captured output</returns>
-	protected virtual async Task ProcessStreamAsync(PipeReader reader, PipeWriter writer, string? conversationId, Activity? parentActivity, CancellationToken cancellationToken)
+	protected virtual async Task ProcessStreamAsync(PipeReader reader, PipeWriter writer, Guid? generatedConversationId, Activity? parentActivity, CancellationToken cancellationToken)
 	{
 		using var activity = StreamTransformerActivitySource.StartActivity("process ask_ai stream", ActivityKind.Internal);
 

src/api/Elastic.Documentation.Api.Infrastructure/Adapters/AskAi/StreamTransformerFactory.cs

@@ -39,9 +39,9 @@ private IStreamTransformer GetTransformer()
 	public string AgentId => GetTransformer().AgentId;
 	public string AgentProvider => GetTransformer().AgentProvider;
 
-	public async Task<Stream> TransformAsync(Stream rawStream, string? conversationId, System.Diagnostics.Activity? parentActivity, Cancel cancellationToken = default)
+	public async Task<Stream> TransformAsync(Stream rawStream, Guid? generatedConversationId, System.Diagnostics.Activity? parentActivity, Cancel cancellationToken = default)
 	{
 		var transformer = GetTransformer();
-		return await transformer.TransformAsync(rawStream, conversationId, parentActivity, cancellationToken);
+		return await transformer.TransformAsync(rawStream, generatedConversationId, parentActivity, cancellationToken);
 	}
 }

src/api/Elastic.Documentation.Api.Infrastructure/ServicesExtension.cs

@@ -173,7 +173,7 @@ private static void AddAskAiUsecase(IServiceCollection services, AppEnv appEnv)
 			logger?.LogInformation("Both stream transformers registered as concrete types");
 
 			// Register factories as interface implementations
-			_ = services.AddScoped<IAskAiGateway<Stream>, AskAiGatewayFactory>();
+			_ = services.AddScoped<IAskAiGateway, AskAiGatewayFactory>();
 			_ = services.AddScoped<IStreamTransformer, StreamTransformerFactory>();
 			logger?.LogInformation("Gateway and transformer factories registered successfully - provider switchable via X-AI-Provider header");