Add virtual model support for multi-key expansion

Virtual models generated from multi-key expansion are now marked and
filtered during config persistence. Virtual models display with a badge
in the UI and cannot be set as default.

pkg/config/config.go

@@ -857,6 +857,10 @@ type ModelConfig struct {
 	secModelName string
 	apiKeys      []string
 	secDirty     bool
+
+	// isVirtual marks this model as a virtual model generated from multi-key expansion.
+	// Virtual models should not be persisted to config files.
+	isVirtual bool
 }
 
 // APIKey returns the first API key from apiKeys
@@ -867,6 +871,11 @@ func (c *ModelConfig) APIKey() string {
 	return ""
 }
 
+// IsVirtual returns true if this model was generated from multi-key expansion.
+func (c *ModelConfig) IsVirtual() bool {
+	return c.isVirtual
+}
+
 // Validate checks if the ModelConfig has all required fields.
 func (c *ModelConfig) Validate() error {
 	if c.ModelName == "" {
@@ -1800,7 +1809,20 @@ func SaveConfig(path string, cfg *Config) error {
 		return err
 	}
 
+	// Filter out virtual models before serializing to config file
+	nonVirtualModels := make([]*ModelConfig, 0, len(cfg.ModelList))
+	for _, m := range cfg.ModelList {
+		if !m.isVirtual {
+			nonVirtualModels = append(nonVirtualModels, m)
+		}
+	}
+	// Temporarily replace ModelList with filtered version for serialization
+	originalModelList := cfg.ModelList
+	cfg.ModelList = nonVirtualModels
+
 	data, err := json.MarshalIndent(cfg, "", "  ")
+	// Restore original ModelList after serialization
+	cfg.ModelList = originalModelList
 	if err != nil {
 		return err
 	}
@@ -2018,6 +2040,7 @@ func expandMultiKeyModels(models []*ModelConfig) []*ModelConfig {
 				RequestTimeout: m.RequestTimeout,
 				ThinkingLevel:  m.ThinkingLevel,
 				ExtraBody:      m.ExtraBody,
+				isVirtual:      true,
 			}
 			expanded = append(expanded, additionalEntry)
 			fallbackNames = append(fallbackNames, expandedName)

pkg/config/config_test.go

@@ -391,6 +391,65 @@ func TestSaveConfig_PreservesDisabledTelegramPlaceholder(t *testing.T) {
 	}
 }
 
+// TestSaveConfig_FiltersVirtualModels verifies that SaveConfig does not write
+// virtual models (generated by expandMultiKeyModels) to the config file.
+func TestSaveConfig_FiltersVirtualModels(t *testing.T) {
+	tmpDir := t.TempDir()
+	path := filepath.Join(tmpDir, "config.json")
+
+	cfg := DefaultConfig()
+
+	// Manually add a virtual model to ModelList (simulating what expandMultiKeyModels does)
+	primaryModel := &ModelConfig{
+		ModelName: "gpt-4",
+		Model:     "openai/gpt-4o",
+		apiKeys:   []string{"key1"},
+	}
+	virtualModel := &ModelConfig{
+		ModelName: "gpt-4__key_1",
+		Model:     "openai/gpt-4o",
+		apiKeys:   []string{"key2"},
+		isVirtual: true,
+	}
+	cfg.ModelList = []*ModelConfig{primaryModel, virtualModel}
+
+	// SaveConfig should filter out virtual models
+	if err := SaveConfig(path, cfg); err != nil {
+		t.Fatalf("SaveConfig failed: %v", err)
+	}
+
+	// Reload and verify
+	reloaded, err := LoadConfig(path)
+	if err != nil {
+		t.Fatalf("LoadConfig failed: %v", err)
+	}
+
+	// Should only have the primary model, not the virtual one
+	if len(reloaded.ModelList) != 1 {
+		t.Fatalf("expected 1 model after reload, got %d", len(reloaded.ModelList))
+	}
+
+	if reloaded.ModelList[0].ModelName != "gpt-4" {
+		t.Errorf("expected model_name 'gpt-4', got %q", reloaded.ModelList[0].ModelName)
+	}
+
+	// Verify virtual model was not persisted
+	for _, m := range reloaded.ModelList {
+		if m.ModelName == "gpt-4__key_1" {
+			t.Errorf("virtual model gpt-4__key_1 should not have been saved")
+		}
+	}
+
+	// Verify the saved file does not contain the virtual model name
+	data, err := os.ReadFile(path)
+	if err != nil {
+		t.Fatalf("ReadFile failed: %v", err)
+	}
+	if strings.Contains(string(data), "gpt-4__key_1") {
+		t.Errorf("saved config should not contain virtual model name 'gpt-4__key_1'")
+	}
+}
+
 // TestConfig_Complete verifies all config fields are set
 func TestConfig_Complete(t *testing.T) {
 	cfg := DefaultConfig()

pkg/config/multikey_test.go

@@ -232,6 +232,78 @@ func TestExpandMultiKeyModels_PreservesOtherFields(t *testing.T) {
 	}
 }
 
+func TestExpandMultiKeyModels_IsVirtualFlag(t *testing.T) {
+	models := []*ModelConfig{
+		{
+			ModelName: "gpt-4",
+			Model:     "openai/gpt-4o",
+			apiKeys:   []string{"key1", "key2", "key3"},
+		},
+	}
+
+	result := expandMultiKeyModels(models)
+
+	// Should expand to 3 models
+	if len(result) != 3 {
+		t.Fatalf("expected 3 models, got %d", len(result))
+	}
+
+	// Primary model should NOT be virtual
+	primary := result[2]
+	if primary.isVirtual {
+		t.Errorf("primary model should not be virtual")
+	}
+	if primary.ModelName != "gpt-4" {
+		t.Errorf("expected primary model_name 'gpt-4', got %q", primary.ModelName)
+	}
+
+	// Virtual models should have isVirtual = true
+	virtual1 := result[0]
+	if !virtual1.isVirtual {
+		t.Errorf("gpt-4__key_1 should be virtual")
+	}
+	if virtual1.ModelName != "gpt-4__key_1" {
+		t.Errorf("expected virtual model_name 'gpt-4__key_1', got %q", virtual1.ModelName)
+	}
+
+	virtual2 := result[1]
+	if !virtual2.isVirtual {
+		t.Errorf("gpt-4__key_2 should be virtual")
+	}
+	if virtual2.ModelName != "gpt-4__key_2" {
+		t.Errorf("expected virtual model_name 'gpt-4__key_2', got %q", virtual2.ModelName)
+	}
+
+	// IsVirtual() method should work
+	if !virtual1.IsVirtual() {
+		t.Errorf("IsVirtual() should return true for virtual model")
+	}
+	if primary.IsVirtual() {
+		t.Errorf("IsVirtual() should return false for primary model")
+	}
+}
+
+func TestExpandMultiKeyModels_SingleKey_NotVirtual(t *testing.T) {
+	models := []*ModelConfig{
+		{
+			ModelName: "gpt-4",
+			Model:     "openai/gpt-4o",
+			apiKeys:   []string{"single-key"},
+		},
+	}
+
+	result := expandMultiKeyModels(models)
+
+	if len(result) != 1 {
+		t.Fatalf("expected 1 model, got %d", len(result))
+	}
+
+	// Single key model should NOT be virtual
+	if result[0].isVirtual {
+		t.Errorf("single key model should not be virtual")
+	}
+}
+
 func TestMergeAPIKeys(t *testing.T) {
 	tests := []struct {
 		name     string