diff --git a/pkg/backends/backend.go b/pkg/backends/backend.go
index 2bb0fa8..6e50565 100644
--- a/pkg/backends/backend.go
+++ b/pkg/backends/backend.go
@@ -56,13 +56,15 @@ func (o *Options) UnmarshalJSON(data []byte) error {
 	}
 
 	// Create backend from constructor map
-	if o.BackendOptions != nil {
-		constructor, exists := backendConstructors[o.BackendType]
-		if !exists {
-			return fmt.Errorf("unsupported backend type: %s", o.BackendType)
-		}
+	constructor, exists := backendConstructors[o.BackendType]
+	if !exists {
+		return fmt.Errorf("unsupported backend type: %s", o.BackendType)
+	}
 
-		backend := constructor()
+	backend := constructor()
+
+	// If backend_options is provided, unmarshal into the backend
+	if o.BackendOptions != nil {
 		optionsData, err := json.Marshal(o.BackendOptions)
 		if err != nil {
 			return fmt.Errorf("failed to marshal backend options: %w", err)
@@ -71,10 +73,11 @@ func (o *Options) UnmarshalJSON(data []byte) error {
 		if err := json.Unmarshal(optionsData, backend); err != nil {
 			return fmt.Errorf("failed to unmarshal backend options: %w", err)
 		}
-
-		// Store in the appropriate typed field for backward compatibility
-		o.setBackendOptions(backend)
 	}
+	// If backend_options is nil or empty, backend remains as empty struct (for router mode)
+
+	// Store in the appropriate typed field
+	o.setBackendOptions(backend)
 
 	return nil
 }
diff --git a/pkg/backends/llama.go b/pkg/backends/llama.go
index 246f0fe..fb94684 100644
--- a/pkg/backends/llama.go
+++ b/pkg/backends/llama.go
@@ -327,20 +327,30 @@ func (o *LlamaServerOptions) UnmarshalJSON(data []byte) error {
 }
 
 func (o *LlamaServerOptions) GetPort() int {
+	if o == nil {
+		return 0
+	}
 	return o.Port
 }
 
 func (o *LlamaServerOptions) SetPort(port int) {
+	if o == nil {
+		return
+	}
 	o.Port = port
 }
 
 func (o *LlamaServerOptions) GetHost() string {
+	if o == nil {
+		return "localhost"
+	}
 	return o.Host
 }
 
 func (o *LlamaServerOptions) Validate() error {
+	// Allow nil options for router mode where llama.cpp manages models dynamically
 	if o == nil {
-		return validation.ValidationError(fmt.Errorf("llama server options cannot be nil for llama.cpp backend"))
+		return nil
 	}
 
 	// Use reflection to check all string fields for injection patterns
@@ -370,6 +380,9 @@ func (o *LlamaServerOptions) Validate() error {
 
 // BuildCommandArgs converts InstanceOptions to command line arguments
 func (o *LlamaServerOptions) BuildCommandArgs() []string {
+	if o == nil {
+		return []string{}
+	}
 	// Llama uses multiple flags for arrays by default (not comma-separated)
 	// Use package-level llamaMultiValuedFlags variable
 	args := BuildCommandArgs(o, llamaMultiValuedFlags)
@@ -381,6 +394,9 @@ func (o *LlamaServerOptions) BuildCommandArgs() []string {
 }
 
 func (o *LlamaServerOptions) BuildDockerArgs() []string {
+	if o == nil {
+		return []string{}
+	}
 	// For llama, Docker args are the same as normal args
 	return o.BuildCommandArgs()
 }