diff --git a/sundynix-mcp-go/internal/rag/milvus.go b/sundynix-mcp-go/internal/rag/milvus.go
index 3ca1a1f..58d37b9 100644
--- a/sundynix-mcp-go/internal/rag/milvus.go
+++ b/sundynix-mcp-go/internal/rag/milvus.go
@@ -3,6 +3,8 @@ package rag
 import (
 	"context"
 	"fmt"
+	"log"
+	"strconv"
 	"sync"
 
 	"github.com/milvus-io/milvus-sdk-go/v2/client"
@@ -44,6 +46,18 @@ func (m *milvusStore) ensure(ctx context.Context, dim int) error {
 	if err != nil {
 		return err
 	}
+	// 已存集合维度不一致（如切换 embedding 模型）→ 重建。
+	if has {
+		if coll, derr := m.cli.DescribeCollection(ctx, collection); derr == nil {
+			if existing := vectorDim(coll); existing != 0 && existing != dim {
+				log.Printf("[rag] 集合维度 %d≠%d，重建 %s", existing, dim, collection)
+				if err := m.cli.DropCollection(ctx, collection); err != nil {
+					return fmt.Errorf("drop collection: %w", err)
+				}
+				has = false
+			}
+		}
+	}
 	if !has {
 		schema := entity.NewSchema().WithName(collection).WithDescription("sundynix wiki vectors").
 			WithField(entity.NewField().WithName("id").WithDataType(entity.FieldTypeInt64).WithIsPrimaryKey(true).WithIsAutoID(true)).
@@ -88,6 +102,22 @@ func (m *milvusStore) insert(ctx context.Context, kb string, texts []string, vec
 	return m.cli.Flush(ctx, collection, false)
 }
 
+// vectorDim 从集合 schema 读出向量字段维度（用于检测维度变化）。
+func vectorDim(coll *entity.Collection) int {
+	if coll == nil || coll.Schema == nil {
+		return 0
+	}
+	for _, f := range coll.Schema.Fields {
+		if f.DataType == entity.FieldTypeFloatVector {
+			if d, ok := f.TypeParams["dim"]; ok {
+				n, _ := strconv.Atoi(d)
+				return n
+			}
+		}
+	}
+	return 0
+}
+
 // Hit 是一条检索结果。
 type Hit struct {
 	Text  string