microsoft/semantic-kernel · error · InvalidOperationException

Failed to resolve function target for {step.GetType().Name},

Error message

Failed to resolve function target for {step.GetType().Name}, {step.Name}: Function - {functionName ?? "any"} / Parameter - {parameterName ?? "any"}

What it means

Thrown by the ProcessFunctionTargetBuilder constructor when step.ResolveFunctionTarget(functionName, parameterName) returns null, meaning no matching kernel function (and optionally parameter) could be found on the step for the given names. The exception message includes the step type, step name, and the function/parameter names that were attempted.

Source

Thrown at dotnet/src/Experimental/Process.Core/ProcessFunctionTargetBuilder.cs:172

    public ProcessFunctionTargetBuilder(ProcessStepBuilder step, string? functionName = null, string? parameterName = null) : base(ProcessTargetType.KernelFunction)
    {
        Verify.NotNull(step, nameof(step));

        this.Step = step;

        // If the step is an EndStep, we don't need to resolve the function target.
        if (step is EndStep)
        {
            this.FunctionName = "END";
            this.ParameterName = null;
            return;
        }

        // Make sure the function target is valid.
        var target = step.ResolveFunctionTarget(functionName, parameterName);
        if (target == null)
        {
            throw new InvalidOperationException($"Failed to resolve function target for {step.GetType().Name}, {step.Name}: Function - {functionName ?? "any"} / Parameter - {parameterName ?? "any"}");
        }

        this.FunctionName = target.FunctionName!;
        this.ParameterName = target.ParameterName;
    }

    /// <summary>
    /// Builds the function target.
    /// </summary>
    /// <returns>An instance of <see cref="KernelProcessFunctionTarget"/></returns>
    internal override KernelProcessTarget Build(ProcessBuilder? processBuilder = null)
    {
        Verify.NotNull(this.Step.Id);
        return new KernelProcessFunctionTarget(this.Step.Id, this.FunctionName, this.ParameterName, this.TargetEventId);
    }

    /// <summary>
    /// An instance of <see cref="ProcessStepBuilder"/> representing the target Step.

View on GitHub (pinned to c028a0c7dc)

Solutions

1. Verify the functionName matches a method decorated with [KernelFunction] on the step type.
2. If functionName is null/omitted, ensure the step has exactly one kernel function so it can be auto-resolved.
3. Check for typos or case mismatches in function and parameter names (they are case-sensitive).
4. Inspect the step's GetFunctionMetadataMap() output to list available function names.

Example fix

// before — function name doesn't exist on step
var target = new ProcessFunctionTargetBuilder(myStep, functionName: "ProcessData");
// throws if step has [KernelFunction] named "HandleData" instead

// after
var target = new ProcessFunctionTargetBuilder(myStep, functionName: "HandleData");

var functionNames = myStep.GetFunctionMetadataMap().Keys;
if (!functionNames.Contains(functionName))
    throw new InvalidOperationException(
        $"Function '{functionName}' not found on step '{myStep.Name}'. Available: {string.Join(", ", functionNames)}");

var target = new ProcessFunctionTargetBuilder(myStep, functionName: functionName, parameterName: parameterName);

bool IsValidFunctionTarget(ProcessStepBuilder step, string? functionName, string? parameterName)
    => step.ResolveFunctionTarget(functionName, parameterName) is not null;

When it happens

Trigger: Creating a ProcessFunctionTargetBuilder with a functionName that does not exist on the step; specifying a functionName for a step whose KernelProcessStep subclass has no [KernelFunction] methods with that name; providing a parameterName that doesn't match any parameter on the function.

Common situations: Typo in the function or parameter name; renaming a [KernelFunction] method without updating process edge definitions; the step type was not loaded or decorated with the expected KernelFunction attributes; version mismatch where a function was removed or renamed in a newer step type.

Related errors

• The target step {this.Name} has no functions.
• Map operation is a process. Use {nameof(ProcessMapBuilder)}.
• The step {this.Name} has no functions.
• The target step has more than one function, so a function na
• The function {functionName} does not exist on step {this.Nam

AI-assisted analysis of microsoft/semantic-kernel@c028a0c7dc (2026-08-13). Data as JSON: /api/errors/d33009d29c37b718. Report an issue: GitHub.