fix(phase-2): add thread-safety to ModelRegistry and Router reload operations

internal/router/router.go

@@ -5,6 +5,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"strings"
+	"sync"
 
 	"gophergate/internal/db"
 )
@@ -32,6 +33,7 @@ type ClassifierFunc func(ctx context.Context, selectorModel, systemPrompt, userM
 
 // Router resolves model groups to concrete models.
 type Router struct {
+	mu       sync.RWMutex
 	groups   map[string]db.ModelGroup
 	classify ClassifierFunc
 }
@@ -50,6 +52,8 @@ func New(groups []db.ModelGroup, classify ClassifierFunc) *Router {
 
 // Groups returns all registered model group IDs.
 func (r *Router) Groups() []string {
+	r.mu.RLock()
+	defer r.mu.RUnlock()
 	ids := make([]string, 0, len(r.groups))
 	for id := range r.groups {
 		ids = append(ids, id)
@@ -59,13 +63,17 @@ func (r *Router) Groups() []string {
 
 // IsGroup returns true if the model name is a group ID.
 func (r *Router) IsGroup(modelID string) bool {
+	r.mu.RLock()
+	defer r.mu.RUnlock()
 	_, ok := r.groups[modelID]
 	return ok
 }
 
 // Route resolves a group to a concrete model.
 func (r *Router) Route(ctx context.Context, groupID string, routeCtx *RouteContext) (*Decision, error) {
+	r.mu.RLock()
 	group, ok := r.groups[groupID]
+	r.mu.RUnlock()
 	if !ok {
 		return nil, fmt.Errorf("unknown model group: %s", groupID)
 	}
@@ -133,8 +141,12 @@ func (r *Router) RouteToConcrete(ctx context.Context, modelID string, routeCtx *
 
 // Reload replaces the group definitions without recreating the router.
 func (r *Router) Reload(groups []db.ModelGroup) {
-	r.groups = make(map[string]db.ModelGroup)
+	newGroups := make(map[string]db.ModelGroup)
 	for _, g := range groups {
-		r.groups[g.ID] = g
+		newGroups[g.ID] = g
 	}
+
+	r.mu.Lock()
+	r.groups = newGroups
+	r.mu.Unlock()
 }