microsoft/semantic-kernel · error · KernelException

Message {messageKey} is not expected for edge group {this._e

Error message

Message {messageKey} is not expected for edge group {this._edgeGroup.GroupId}.

What it means

Thrown by LocalEdgeGroupProcessor.TryGetResult when an incoming message's key (composed as '{SourceId}.{SourceEventId}') is not present in the edge group's required message sources. The edge group collects messages from multiple source steps and only fires when all declared sources have delivered their messages; this error means a message arrived from a source/event combination the group was not configured to accept.

Source

Thrown at dotnet/src/Experimental/Process.LocalRuntime/LocalEdgeGroupProcessor.cs:28

    private readonly KernelProcessEdgeGroup _edgeGroup;
    private readonly Dictionary<string, object?> _messageData = [];
    private HashSet<string> _requiredMessages = [];
    private HashSet<string> _absentMessages = [];

    public LocalEdgeGroupProcessor(KernelProcessEdgeGroup edgeGroup)
    {
        Verify.NotNull(edgeGroup, nameof(edgeGroup));
        this._edgeGroup = edgeGroup;

        this.InitializeEventTracking();
    }

    public bool TryGetResult(ProcessMessage message, out Dictionary<string, object?>? result)
    {
        string messageKey = this.GetKeyForMessageSource(message);
        if (!this._requiredMessages.Contains(messageKey))
        {
            throw new KernelException($"Message {messageKey} is not expected for edge group {this._edgeGroup.GroupId}.");
        }

        this._messageData[messageKey] = (message.TargetEventData as KernelProcessEventData)!.ToObject();

        this._absentMessages.Remove(messageKey);
        if (this._absentMessages.Count == 0)
        {
            // We have received all required events so forward them to the target
            result = (Dictionary<string, object?>?)this._edgeGroup.InputMapping(this._messageData);

            // TODO: Reset state according to configured logic i.e. reset after first message or after all messages are received.
            this.InitializeEventTracking();

            return true;
        }

        result = null;
        return false;

View on GitHub (pinned to c028a0c7dc)

Solutions

Compare the message's SourceId and SourceEventId against each entry in the edge group's MessageSources (which use SourceStepId.MessageType) and correct whichever side is wrong.
Verify that the edge defining the source-to-group routing uses the exact event id the source step emits.
Check that the GroupId on the outgoing edges matches the group registered on the target step's IncomingEdgeGroups.
If you renamed a step or event, update all KernelProcessEdgeGroup.MessageSources entries that reference the old names.

Example fix

// before - MessageSources references the wrong event id
group.AddEdgeSource(new KernelProcessMessageSource { SourceStepId = "MyStep", MessageType = "ProcessEventA" });
// after - corrected to match what MyStep actually emits
group.AddEdgeSource(new KernelProcessMessageSource { SourceStepId = "MyStep", MessageType = "ProcessEventB" });

Defensive patterns

Strategy: validation

Validate before calling

// Validate that each source step/event feeding an edge group is declared in the group's MessageSources
foreach (var group in step.IncomingEdgeGroups.Values)
{
    foreach (var source in group.MessageSources)
    {
        var expectedKey = $"{source.SourceStepId}.{source.MessageType}";
        // Ensure an edge exists from source.SourceStepId emitting source.MessageType into this step with this group
        var matchingEdge = process.Edges
            .SelectMany(kvp => kvp.Value)
            .Where(e => e.Source.EventId == source.MessageType && e.OutputTarget.StepId == step.State.Id)
            .Any();
        if (!matchingEdge) { /* log or throw configuration error */ }
    }
}

Prevention

After building the process, iterate all edge groups and verify every MessageSource has a corresponding edge.
Use a process-builder validation pass before StartAsync to catch source/event mismatches early.
Keep step ids and event ids stable across refactors; update edge group definitions when renaming.

When it happens

Trigger: A ProcessMessage is routed to a step whose KernelProcessEdgeGroup is registered, but the message's SourceId + SourceEventId pair does not match any KernelProcessMessageSource declared in the group's MessageSources list. This occurs when an edge connects a source step to a grouped target but the source's event id or step id does not align with what the group expects.

Common situations: Renaming a step or event id without updating the edge group's MessageSources; wiring an edge to a grouped input using the wrong event id; version changes where the emitted event id changed but the group definition was not migrated; a message from an unrelated source step accidentally sharing the same GroupId.

Related errors

AI-assisted analysis of microsoft/semantic-kernel@c028a0c7dc (2026-08-13). Data as JSON: /api/errors/60e8013015e66396. Report an issue: GitHub.