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Merged
peibekwe merged 1 commit into from
Jul 15, 2026
Merged

Fix message ordering in workflow-hosted agents #7123

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141 changes: 53 additions & 88 deletions dotnet/src/Microsoft.Agents.AI.Workflows/MessageMerger.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -4,159 +4,123 @@
using System.Collections.Generic;
using System.Linq;
using Microsoft.Extensions.AI;
using Microsoft.Shared.Diagnostics;

namespace Microsoft.Agents.AI.Workflows;

internal sealed class MessageMerger
{
private sealed class ResponseMergeState(string? responseId)
private sealed class MessageMergeState(string? messageId)
{
public string? ResponseId { get; } = responseId;
public string? MessageId { get; } = messageId;

public Dictionary<string, List<AgentResponseUpdate>> UpdatesByMessageId { get; } = [];
public List<AgentResponseUpdate> DanglingUpdates { get; } = [];
public List<AgentResponseUpdate> Updates { get; } = [];

public void AddUpdate(AgentResponseUpdate update)
public AgentResponse ComputeMerged(string? responseId)
{
if (update.MessageId is null)
if (this.Updates.Count == 0)
{
this.DanglingUpdates.Add(update);
throw new InvalidOperationException($"No updates found for message ID '{this.MessageId}' in response '{responseId}'.");
}
else
{
if (!this.UpdatesByMessageId.TryGetValue(update.MessageId, out List<AgentResponseUpdate>? updates))
{
this.UpdatesByMessageId[update.MessageId] = updates = [];
}

updates.Add(update);
}
return this.Updates.ToAgentResponse();
}
}

public AgentResponse ComputeMerged(string messageId)
{
if (this.UpdatesByMessageId.TryGetValue(Throw.IfNull(messageId), out List<AgentResponseUpdate>? updates))
{
return updates.ToAgentResponse();
}
private sealed class ResponseMergeState(string? responseId)
{
private readonly Dictionary<string, MessageMergeState> _messageStates = [];
private readonly List<MessageMergeState> _messageStatesInOrder = [];
private MessageMergeState? _lastObservedState;

throw new KeyNotFoundException($"No updates found for message ID '{messageId}' in response '{this.ResponseId}'.");
}
public string? ResponseId { get; } = responseId;

public AgentResponse ComputeDangling()
public void AddUpdate(AgentResponseUpdate update)
{
if (this.DanglingUpdates.Count == 0)
{
throw new InvalidOperationException("No dangling updates to compute a response from.");
}

return this.DanglingUpdates.ToAgentResponse();
MessageMergeState state = this.GetOrCreateMessageState(update.MessageId);
state.Updates.Add(update);
this._lastObservedState = state;
}

public List<ChatMessage> ComputeFlattened()
private MessageMergeState GetOrCreateMessageState(string? messageId)
{
List<ChatMessage> result = this.UpdatesByMessageId.Keys.SelectMany(AggregateUpdatesToMessage).ToList();
if (this.DanglingUpdates.Count > 0)
{
result.AddRange(this.ComputeDangling().Messages);
}

return result;

IList<ChatMessage> AggregateUpdatesToMessage(string messageId)
if (messageId is null)
{
List<AgentResponseUpdate> updates = this.UpdatesByMessageId[messageId];
if (updates.Count == 0)
if (this._lastObservedState is { MessageId: null })
{
throw new InvalidOperationException($"No updates found for message ID '{messageId}' in response '{this.ResponseId}'.");
return this._lastObservedState;
}

return updates.Select(oldUpdate => oldUpdate.AsChatResponseUpdate()).ToChatResponse().Messages;
MessageMergeState state = new(null);
this._messageStatesInOrder.Add(state);
return state;
}

if (!this._messageStates.TryGetValue(messageId, out MessageMergeState? existingState))
{
existingState = new(messageId);
this._messageStates[messageId] = existingState;
this._messageStatesInOrder.Add(existingState);
}

return existingState;
}

public List<AgentResponse> ComputeMerged()
=> this._messageStatesInOrder.ConvertAll(state => state.ComputeMerged(this.ResponseId));

public List<ChatMessage> ComputeFlattened()
=> this.ComputeMerged().SelectMany(response => response.Messages).ToList();
}

private readonly Dictionary<string, ResponseMergeState> _mergeStates = [];
private readonly List<string> _responseIdsInOrder = [];
private readonly ResponseMergeState _danglingState = new(null);

public void AddUpdate(AgentResponseUpdate update)
{
if (update.ResponseId is null)
{
this._danglingState.DanglingUpdates.Add(update);
this._danglingState.AddUpdate(update);
}
else
{
if (!this._mergeStates.TryGetValue(update.ResponseId, out ResponseMergeState? state))
{
this._mergeStates[update.ResponseId] = state = new ResponseMergeState(update.ResponseId);
this._responseIdsInOrder.Add(update.ResponseId);
}

state.AddUpdate(update);
}
}

private int CompareByDateTimeOffset(AgentResponse left, AgentResponse right)
{
const int LESS = -1, EQ = 0, GREATER = 1;

if (left.CreatedAt == right.CreatedAt)
{
return EQ;
}

if (!left.CreatedAt.HasValue)
{
return GREATER;
}

if (!right.CreatedAt.HasValue)
{
return LESS;
}

return left.CreatedAt.Value.CompareTo(right.CreatedAt.Value);
}

public AgentResponse ComputeMerged(string primaryResponseId, string? primaryAgentId = null, string? primaryAgentName = null)
{
List<ChatMessage> messages = [];
Dictionary<string, AgentResponse> responses = [];
List<AgentResponse> responses = [];
HashSet<string> agentIds = [];
HashSet<ChatFinishReason> finishReasons = [];

foreach (string responseId in this._mergeStates.Keys)
foreach (string responseId in this._responseIdsInOrder)
{
ResponseMergeState mergeState = this._mergeStates[responseId];

List<AgentResponse> responseList = mergeState.UpdatesByMessageId.Keys.Select(mergeState.ComputeMerged).ToList();
if (mergeState.DanglingUpdates.Count > 0)
{
responseList.Add(mergeState.ComputeDangling());
}

responseList.Sort(this.CompareByDateTimeOffset);
responses[responseId] = responseList.Aggregate(MergeResponses);
messages.AddRange(GetMessagesWithCreatedAt(responses[responseId]));
List<AgentResponse> responseList = mergeState.ComputeMerged();
AgentResponse response = responseList.Aggregate(MergeResponses);
responses.Add(response);
messages.AddRange(GetMessagesWithCreatedAt(response));
}

UsageDetails? usage = null;
AdditionalPropertiesDictionary? additionalProperties = null;
HashSet<DateTimeOffset> createdTimes = [];

foreach (AgentResponse response in responses.Values)
foreach (AgentResponse response in responses)
{
if (response.AgentId is not null)
{
agentIds.Add(response.AgentId);
}

if (response.CreatedAt.HasValue)
{
createdTimes.Add(response.CreatedAt.Value);
}

if (response.FinishReason.HasValue)
{
finishReasons.Add(response.FinishReason.Value);
Expand Down Expand Up @@ -242,8 +206,9 @@ static IEnumerable<ChatMessage> GetMessagesWithCreatedAt(AgentResponse response)
AuthorName = message.AuthorName,
Contents = message.Contents,
MessageId = message.MessageId,
CreatedAt = createdAt,
RawRepresentation = message.RawRepresentation
CreatedAt = message.CreatedAt ?? createdAt,
RawRepresentation = message.RawRepresentation,
AdditionalProperties = message.AdditionalProperties
});
}

Expand Down
10 changes: 5 additions & 5 deletions dotnet/src/Microsoft.Agents.AI.Workflows/Specialized/HandoffAgentExecutor.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -427,10 +427,9 @@ private async ValueTask<AgentInvocationResult> InvokeAgentAsync(IEnumerable<Chat
AgentResponse response;

AIAgentUnservicedRequestsCollector collector = new(this._userInputHandler, this._functionCallHandler);

string? requestedHandoff = null;
List<AgentResponseUpdate> updates = [];
List<FunctionCallContent> candidateRequests = [];
List<(FunctionCallContent Request, string? ResponseId)> candidateRequests = [];

this._session ??= await this._agent.CreateSessionAsync(cancellationToken).ConfigureAwait(false);

Expand All @@ -448,7 +447,7 @@ bool CollectHandoffRequestsFilter(FunctionCallContent candidateHandoffRequest)
bool isHandoffRequest = this._handoffFunctionNames.Contains(candidateHandoffRequest.Name);
if (isHandoffRequest)
{
candidateRequests.Add(candidateHandoffRequest);
candidateRequests.Add((candidateHandoffRequest, update.ResponseId));
}

return !isHandoffRequest;
Expand All @@ -457,13 +456,13 @@ bool CollectHandoffRequestsFilter(FunctionCallContent candidateHandoffRequest)

if (candidateRequests.Count > 1)
{
string message = $"Duplicate handoff requests in single turn ([{string.Join(", ", candidateRequests.Select(request => request.Name))}]). Using last ({candidateRequests.Last().Name})";
string message = $"Duplicate handoff requests in single turn ([{string.Join(", ", candidateRequests.Select(candidate => candidate.Request.Name))}]). Using last ({candidateRequests.Last().Request.Name})";
await context.AddEventAsync(new WorkflowWarningEvent(message), cancellationToken).ConfigureAwait(false);
}

if (candidateRequests.Count > 0)
{
FunctionCallContent handoffRequest = candidateRequests[candidateRequests.Count - 1];
(FunctionCallContent handoffRequest, string? handoffResponseId) = candidateRequests[candidateRequests.Count - 1];
requestedHandoff = handoffRequest.Name;

await AddUpdateAsync(
Expand All @@ -474,6 +473,7 @@ await AddUpdateAsync(
Contents = [CreateHandoffResult(handoffRequest.CallId)],
CreatedAt = DateTimeOffset.UtcNow,
MessageId = Guid.NewGuid().ToString("N"),
ResponseId = handoffResponseId,
Role = ChatRole.Tool,
},
cancellationToken
Expand Down
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