microsoft/semantic-kernel · error · KernelException

The edge target is not a function target: {e.OutputTarget}

Error message

The edge target is not a function target: {e.OutputTarget}

What it means

Thrown by `BuildNode` while mapping a step's edges to `ThenAction`s: an edge's `OutputTarget` is not a `KernelProcessFunctionTarget`. The declarative workflow only supports edges that target a kernel function, so any other target type is rejected. It is a KernelException raised inside the edge-projection lambda.

Source

Thrown at dotnet/src/Experimental/Process.Core/Workflow/WorkflowBuilder.cs:454

                    From = step.State.Id,
                    Event = edge.Key,
                    Condition = edge.Value.FirstOrDefault()?.Condition.DeclarativeDefinition
                },
                Then = [.. edge.Value.Select(e =>
                {
                    if (e.OutputTarget is KernelProcessFunctionTarget functionTarget)
                    {
                        return new ThenAction()
                        {
                            Node = functionTarget.StepId switch
                            {
                                ProcessConstants.EndStepName => "End",
                                string s => s
                            }
                        };
                    }

                    throw new KernelException($"The edge target is not a function target: {e.OutputTarget}");
                })]
            };

            orchestrationSteps.Add(orchestrationStep);
        }

        return node;
    }

    private static Node BuildAgentNode(KernelProcessAgentStep agentStep, List<OrchestrationStep> orchestrationSteps)
    {
        Verify.NotNull(agentStep);

        if (agentStep.AgentDefinition is null || string.IsNullOrWhiteSpace(agentStep.State?.Id) || string.IsNullOrWhiteSpace(agentStep.AgentDefinition.Type))
        {
            throw new InvalidOperationException("Attempt to build a workflow node from step with no Id");
        }

View on GitHub (pinned to c028a0c7dc)

Solutions

1. Ensure every edge is created with a `KernelProcessFunctionTarget` as its `OutputTarget` (use the standard `.SendEventTo(...)` / target-builder APIs).
2. If you have custom target types, convert them to `KernelProcessFunctionTarget` before calling `BuildWorkflow`.
3. Audit edge construction to confirm no null or non-function targets exist.

Example fix

// before
edge.OutputTarget = new MyCustomTarget();
// after
edge.OutputTarget = new KernelProcessFunctionTarget { StepId = "NextStep", FunctionName = "Run" };

foreach (var step in process.Steps)
{
    foreach (var edge in step.Edges.SelectMany(e => e.Value))
    {
        if (edge.OutputTarget is not KernelProcessFunctionTarget)
            throw new InvalidOperationException($"Edge on step '{step.State?.Id}' has a non-function output target ({edge.OutputTarget?.GetType().Name}).");
    }
}

bool HasFunctionTargets(KernelProcessStepInfo step) =>
    step.Edges.SelectMany(e => e.Value).All(e => e.OutputTarget is KernelProcessFunctionTarget);

try { await WorkflowBuilder.BuildWorkflow(process); }
catch (KernelException ex) when (ex.Message.Contains("not a function target"))
{ _logger.LogError(ex, "An edge target is not a KernelProcessFunctionTarget."); throw; }

When it happens

Trigger: Construct a process edge whose `OutputTarget` is null or an unsupported subtype of the target base; programmatically build edges with a custom target type instead of `KernelProcessFunctionTarget`; deserialize a process whose edge targets lost their concrete type.

Common situations: Custom edge-target subclasses introduced without updating the builder; serialization polymorphism dropping the concrete function-target type; mixing runtimes that emit different target shapes.

Related errors

• The process must have an Id set
• Unsupported target type
• An orchestration is referencing a node with Id `{listenCondi
• A complete then action is required for orchestration steps.
• An orchestration is referencing a node with Id `{action.Node

AI-assisted analysis of microsoft/semantic-kernel@c028a0c7dc (2026-08-13). Data as JSON: /api/errors/3aa1b8464df71b96. Report an issue: GitHub.