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.NET: Durable Agent samples and automated validation for non-Azure Functions (#3042)
* Durable Agent samples and automated validation for non-Azure Functions * Update test projects * fix file encoding * Remove AgentThreadMetadata usage * Absorb breaking change from #3152 * Absorb newer breaking changes (AgentRunResponse --> AgentResponse) * Absorb more breaking changes (see #3222) * Improve integration test reliability (isolated task hubs, etc.) * Fix flakey streaming test --------- Co-authored-by: Mark Wallace <127216156+markwallace-microsoft@users.noreply.github.com>
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Chris Gillum
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// Copyright (c) Microsoft. All rights reserved.
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using System.Runtime.CompilerServices;
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using Microsoft.Agents.AI;
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using Microsoft.Agents.AI.DurableTask;
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using StackExchange.Redis;
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namespace ReliableStreaming;
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/// <summary>
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/// Represents a chunk of data read from a Redis stream.
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/// </summary>
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/// <param name="EntryId">The Redis stream entry ID (can be used as a cursor for resumption).</param>
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/// <param name="Text">The text content of the chunk, or null if this is a completion/error marker.</param>
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/// <param name="IsDone">True if this chunk marks the end of the stream.</param>
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/// <param name="Error">An error message if something went wrong, or null otherwise.</param>
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public readonly record struct StreamChunk(string EntryId, string? Text, bool IsDone, string? Error);
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/// <summary>
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/// An implementation of <see cref="IAgentResponseHandler"/> that publishes agent response updates
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/// to Redis Streams for reliable delivery. This enables clients to disconnect and reconnect
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/// to ongoing agent responses without losing messages.
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/// </summary>
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/// <remarks>
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/// <para>
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/// Redis Streams provide a durable, append-only log that supports consumer groups and message
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/// acknowledgment. This implementation uses auto-generated IDs (which are timestamp-based)
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/// as sequence numbers, allowing clients to resume from any point in the stream.
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/// </para>
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/// <para>
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/// Each agent session gets its own Redis Stream, keyed by session ID. The stream entries
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/// contain text chunks extracted from <see cref="AgentResponseUpdate"/> objects.
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/// </para>
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/// </remarks>
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public sealed class RedisStreamResponseHandler : IAgentResponseHandler
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{
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private const int MaxEmptyReads = 300; // 5 minutes at 1 second intervals
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private const int PollIntervalMs = 1000;
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private readonly IConnectionMultiplexer _redis;
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private readonly TimeSpan _streamTtl;
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/// <summary>
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/// Initializes a new instance of the <see cref="RedisStreamResponseHandler" /> class.
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/// </summary>
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/// <param name="redis">The Redis connection multiplexer.</param>
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/// <param name="streamTtl">The time-to-live for stream entries. Streams will expire after this duration of inactivity.</param>
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public RedisStreamResponseHandler(IConnectionMultiplexer redis, TimeSpan streamTtl)
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{
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this._redis = redis;
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this._streamTtl = streamTtl;
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}
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/// <inheritdoc/>
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public async ValueTask OnStreamingResponseUpdateAsync(
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IAsyncEnumerable<AgentResponseUpdate> messageStream,
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CancellationToken cancellationToken)
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{
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// Get the current session ID from the DurableAgentContext
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// This is set by the AgentEntity before invoking the response handler
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DurableAgentContext context = DurableAgentContext.Current
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?? throw new InvalidOperationException("DurableAgentContext.Current is not set. This handler must be used within a durable agent context.");
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// Get conversation ID from the current thread context, which is only available in the context of
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// a durable agent execution.
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string conversationId = context.CurrentThread.GetService<AgentSessionId>().ToString();
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if (string.IsNullOrEmpty(conversationId))
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{
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throw new InvalidOperationException("Unable to determine conversation ID from the current thread.");
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}
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string streamKey = GetStreamKey(conversationId);
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IDatabase db = this._redis.GetDatabase();
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int sequenceNumber = 0;
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await foreach (AgentResponseUpdate update in messageStream.WithCancellation(cancellationToken))
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{
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// Extract just the text content - this avoids serialization round-trip issues
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string text = update.Text;
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// Only publish non-empty text chunks
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if (!string.IsNullOrEmpty(text))
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{
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// Create the stream entry with the text and metadata
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NameValueEntry[] entries =
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[
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new NameValueEntry("text", text),
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new NameValueEntry("sequence", sequenceNumber++),
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new NameValueEntry("timestamp", DateTimeOffset.UtcNow.ToUnixTimeMilliseconds()),
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];
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// Add to the Redis Stream with auto-generated ID (timestamp-based)
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await db.StreamAddAsync(streamKey, entries);
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// Refresh the TTL on each write to keep the stream alive during active streaming
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await db.KeyExpireAsync(streamKey, this._streamTtl);
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}
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}
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// Add a sentinel entry to mark the end of the stream
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NameValueEntry[] endEntries =
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[
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new NameValueEntry("text", ""),
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new NameValueEntry("sequence", sequenceNumber),
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new NameValueEntry("timestamp", DateTimeOffset.UtcNow.ToUnixTimeMilliseconds()),
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new NameValueEntry("done", "true"),
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];
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await db.StreamAddAsync(streamKey, endEntries);
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// Set final TTL - the stream will be cleaned up after this duration
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await db.KeyExpireAsync(streamKey, this._streamTtl);
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}
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/// <inheritdoc/>
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public ValueTask OnAgentResponseAsync(AgentResponse message, CancellationToken cancellationToken)
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{
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// This handler is optimized for streaming responses.
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// For non-streaming responses, we don't need to store in Redis since
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// the response is returned directly to the caller.
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return ValueTask.CompletedTask;
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}
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/// <summary>
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/// Reads chunks from a Redis stream for the given session, yielding them as they become available.
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/// </summary>
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/// <param name="conversationId">The conversation ID to read from.</param>
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/// <param name="cursor">Optional cursor to resume from. If null, reads from the beginning.</param>
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/// <param name="cancellationToken">Cancellation token.</param>
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/// <returns>An async enumerable of stream chunks.</returns>
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public async IAsyncEnumerable<StreamChunk> ReadStreamAsync(
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string conversationId,
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string? cursor,
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[EnumeratorCancellation] CancellationToken cancellationToken)
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{
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string streamKey = GetStreamKey(conversationId);
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IDatabase db = this._redis.GetDatabase();
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string startId = string.IsNullOrEmpty(cursor) ? "0-0" : cursor;
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int emptyReadCount = 0;
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bool hasSeenData = false;
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while (!cancellationToken.IsCancellationRequested)
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{
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StreamEntry[]? entries = null;
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string? errorMessage = null;
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try
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{
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entries = await db.StreamReadAsync(streamKey, startId, count: 100);
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}
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catch (Exception ex)
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{
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errorMessage = ex.Message;
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}
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if (errorMessage != null)
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{
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yield return new StreamChunk(startId, null, false, errorMessage);
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yield break;
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}
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// entries is guaranteed to be non-null if errorMessage is null
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if (entries!.Length == 0)
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{
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if (!hasSeenData)
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{
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emptyReadCount++;
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if (emptyReadCount >= MaxEmptyReads)
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{
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yield return new StreamChunk(
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startId,
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null,
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false,
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$"Stream not found or timed out after {MaxEmptyReads * PollIntervalMs / 1000} seconds");
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yield break;
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}
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}
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await Task.Delay(PollIntervalMs, cancellationToken);
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continue;
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}
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hasSeenData = true;
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foreach (StreamEntry entry in entries)
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{
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startId = entry.Id.ToString();
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string? text = entry["text"];
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string? done = entry["done"];
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if (done == "true")
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{
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yield return new StreamChunk(startId, null, true, null);
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yield break;
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}
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if (!string.IsNullOrEmpty(text))
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{
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yield return new StreamChunk(startId, text, false, null);
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}
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}
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}
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// If we exited the loop due to cancellation, throw to signal the caller
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cancellationToken.ThrowIfCancellationRequested();
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}
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/// <summary>
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/// Gets the Redis Stream key for a given conversation ID.
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/// </summary>
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/// <param name="conversationId">The conversation ID.</param>
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/// <returns>The Redis Stream key.</returns>
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internal static string GetStreamKey(string conversationId) => $"agent-stream:{conversationId}";
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}
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