microsoft/semantic-kernel · error · ArgumentException

A complete on_complete condition is required for declarative

Error message

A complete on_complete condition is required for declarative steps.

What it means

Thrown in the OnComplete branch of BuildDeclarativeStepAsync when node.OnComplete is non-null but contains an entry that is null or whose OnCondition is null. Declarative steps require each on_complete entry to carry a complete condition.

Source

Thrown at dotnet/src/Experimental/Process.Core/Workflow/WorkflowBuilder.cs:148

            var endBuilder = processBuilder.AddEndStep();
            this._stepBuilders["End"] = endBuilder;
            return Task.CompletedTask;
        }

        AgentDefinition? agentDefinition = node.Agent ?? throw new KernelException("Declarative steps must have an agent defined.");
        var stepBuilder = processBuilder.AddStepFromAgent(agentDefinition, node.Id);
        if (stepBuilder is not ProcessAgentBuilder agentBuilder)
        {
            throw new KernelException($"Failed to build step from agent definition: {node.Id}");
        }

        // ########################### Parsing on_complete and on_error conditions ###########################

        if (node.OnComplete != null)
        {
            if (node.OnComplete.Any(c => c is null || c.OnCondition is null))
            {
                throw new ArgumentException("A complete on_complete condition is required for declarative steps.");
            }

            agentBuilder.OnComplete([.. node.OnComplete.Select(c => c.OnCondition!)]);
        }

        if (node.OnError != null)
        {
            if (node.OnError.Any(c => c is null || c.OnCondition is null))
            {
                throw new ArgumentException("A complete on_complete condition is required for declarative steps.");
            }

            agentBuilder.OnComplete([.. node.OnError.Select(c => c.OnCondition!)]);
        }

        // ########################### Parsing node inputs ###########################

        if (node.Inputs != null)

View on GitHub (pinned to c028a0c7dc)

Solutions

Ensure every on_complete entry has a non-null element with a populated on_condition.
Remove empty/null on_complete entries from the workflow definition.
Validate OnComplete entries before building: node.OnComplete.All(c => c is not null && c.OnCondition is not null).

Example fix

// before
node.OnComplete = new[] { new CompleteCondition { OnCondition = null } };

// after
node.OnComplete = new[] { new CompleteCondition { OnCondition = myCondition } };

Defensive patterns

Strategy: validation

Validate before calling

if (node.OnComplete is not null && node.OnComplete.Any(c => c is null || c.OnCondition is null))
    throw new ArgumentException("Each on_complete entry needs a complete condition.");

Type guard

static bool OnCompleteIsValid(Node n) => n.OnComplete is null || n.OnComplete.All(c => c is not null && c.OnCondition is not null);

Try / catch

try { await builder.BuildProcessAsync(workflow, yaml); }
catch (ArgumentException ex) when (ex.Message.Contains("on_complete condition is required"))
{ /* fill or remove incomplete on_complete entries */ }

Prevention

Author on_complete entries from a template that mandates on_condition.
Strip null/empty conditions during a pre-build normalization pass.
Add schema validation for the workflow YAML.

When it happens

Trigger: A declarative node whose 'on_complete' array has a null element or an element with a null/missing 'on_condition'.

Common situations: Workflow YAML listing on_complete entries where one omits the condition object; deserialization producing partial entries; copy-paste errors leaving an empty condition block.

Related errors

AI-assisted analysis of microsoft/semantic-kernel@c028a0c7dc (2026-08-13). Data as JSON: /api/errors/1e1eca91dc7c31cc. Report an issue: GitHub.