fix(composer): expand template expressions in elicitation messages

pkg/vmcp/composer/elicitation_integration_test.go

@@ -527,3 +527,61 @@ func TestDefaultElicitationHandler_SDKErrorHandling(t *testing.T) {
 		})
 	}
 }
+
+func TestWorkflowEngine_ElicitationMessageTemplateExpansion(t *testing.T) {
+	t.Parallel()
+
+	te := newTestEngine(t)
+	mockSDK := mocks.NewMockSDKElicitationRequester(te.Ctrl)
+
+	// Capture the elicitation request to verify the message was expanded
+	var capturedReq mcp.ElicitationRequest
+	mockSDK.EXPECT().RequestElicitation(gomock.Any(), gomock.Any()).DoAndReturn(
+		func(_ context.Context, req mcp.ElicitationRequest) (*mcp.ElicitationResult, error) {
+			capturedReq = req
+			return &mcp.ElicitationResult{
+				ElicitationResponse: mcp.ElicitationResponse{
+					Action:  mcp.ElicitationResponseActionAccept,
+					Content: map[string]any{"confirmed": true},
+				},
+			}, nil
+		},
+	)
+
+	handler := NewDefaultElicitationHandler(mockSDK)
+	stateStore := NewInMemoryStateStore(1*time.Minute, 1*time.Hour)
+	engine := NewWorkflowEngine(te.Router, te.Backend, handler, stateStore, nil, nil)
+
+	workflow := &WorkflowDefinition{
+		Name: "template-elicit",
+		Steps: []WorkflowStep{
+			{
+				ID:   "ask",
+				Type: StepTypeElicitation,
+				Elicitation: &ElicitationConfig{
+					Message: "Deploy {{.params.repo}} to {{.params.env}}?",
+					Schema: map[string]any{
+						"type": "object",
+						"properties": map[string]any{
+							"confirmed": map[string]any{"type": "boolean"},
+						},
+					},
+					Timeout: 1 * time.Minute,
+				},
+			},
+		},
+	}
+
+	params := map[string]any{
+		"repo": "acme/widget",
+		"env":  "production",
+	}
+
+	result, err := engine.ExecuteWorkflow(context.Background(), workflow, params)
+	require.NoError(t, err)
+	assert.Equal(t, WorkflowStatusCompleted, result.Status)
+
+	// Verify that template placeholders were expanded in the message
+	assert.Equal(t, "Deploy acme/widget to production?", capturedReq.Params.Message,
+		"elicitation message should have template expressions expanded")
+}

pkg/vmcp/composer/workflow_engine.go

@@ -634,6 +634,21 @@ func (e *workflowEngine) executeElicitationStep(
 		return err
 	}
 
+	// Expand template expressions in elicitation message (e.g. {{.params.owner}})
+	if step.Elicitation.Message != "" {
+		wrapper := map[string]any{"message": step.Elicitation.Message}
+		expanded, expandErr := e.templateExpander.Expand(ctx, wrapper, workflowCtx)
+		if expandErr != nil {
+			err := fmt.Errorf("%w: failed to expand elicitation message for step %s: %v",
+				ErrTemplateExpansion, step.ID, expandErr)
+			workflowCtx.RecordStepFailure(step.ID, err)
+			return err
+		}
+		if msg, ok := expanded["message"].(string); ok {
+			step.Elicitation.Message = msg
+		}
+	}
+
 	// Request elicitation (synchronous - blocks until response or timeout)
 	// Per MCP 2025-06-18: SDK handles JSON-RPC ID correlation internally
 	response, err := e.elicitationHandler.RequestElicitation(ctx, workflowCtx.WorkflowID, step.ID, step.Elicitation)