Bugfixes and improved alignment with architecture blueprint

internal/prompt/go_renderer.go

@@ -13,6 +13,7 @@ var (
 	ErrMissingRequiredInput = errors.New("missing required input artifact")
 	ErrUnknownInput         = errors.New("referenced unknown input artifact")
 	ErrInvalidTemplate      = errors.New("invalid prompt template")
+	ErrRenderFailure        = errors.New("prompt render failure")
 	ErrInvalidMessageRole   = errors.New("invalid or empty message role")
 )
 
@@ -23,9 +24,14 @@ func NewGoRenderer() Renderer {
 }
 
 func (r *goRenderer) Render(ctx context.Context, profile *domain.PromptProfile, inputs map[string]*domain.Artifact, vars map[string]string) (*domain.RenderedPrompt, error) {
+	if profile == nil {
+		return nil, fmt.Errorf("%w: nil profile", ErrRenderFailure)
+	}
+
 	// 1. Verify required inputs
 	for _, req := range profile.ExpectedInputs {
-		if _, ok := inputs[req]; !ok {
+		art, ok := inputs[req]
+		if !ok || art == nil {
 			return nil, fmt.Errorf("%w: %s", ErrMissingRequiredInput, req)
 		}
 	}
@@ -44,19 +50,25 @@ func (r *goRenderer) Render(ctx context.Context, profile *domain.PromptProfile,
 	var renderedMessages []domain.RenderedMessage
 
 	for i, tmplMsg := range profile.Templates {
+		select {
+		case <-ctx.Done():
+			return nil, ctx.Err()
+		default:
+		}
+
 		if tmplMsg.Role == "" {
 			return nil, fmt.Errorf("%w: message %d", ErrInvalidMessageRole, i)
 		}
 
 		// Parse and execute template
-		tmpl, err := template.New(fmt.Sprintf("msg_%d", i)).Funcs(funcs).Parse(tmplMsg.Content)
+		tmpl, err := template.New(fmt.Sprintf("msg_%d", i)).Funcs(funcs).Option("missingkey=error").Parse(tmplMsg.Content)
 		if err != nil {
 			return nil, fmt.Errorf("%w: message %d: %v", ErrInvalidTemplate, i, err)
 		}
 
 		var buf bytes.Buffer
 		if err := tmpl.Execute(&buf, vars); err != nil {
-			return nil, fmt.Errorf("execution failed for message %d: %v", i, err)
+			return nil, fmt.Errorf("%w: message %d: %w", ErrRenderFailure, i, err)
 		}
 
 		renderedMessages = append(renderedMessages, domain.RenderedMessage{