Merge pull request #4839 from visa2/fix/composite-route-prefix-passthrough

fix(composite): pass the requested model through when a prefix route leaves upstream_model empty

backend/internal/service/admin_service_group_test.go

@@ -1588,7 +1588,8 @@ func TestAdminService_CreateCompositeRoute_NormalizesAndPersists(t *testing.T) {
 	require.Equal(t, "router/gpt-", route.PublicModel)
 	require.Equal(t, CompositeRouteMatchPrefix, route.MatchType)
 	require.Equal(t, PlatformOpenAI, route.TargetPlatform)
-	require.Equal(t, "router/gpt-", route.UpstreamModel)
+	// prefix 路由留空 upstream_model 不再回填 public_model：留空表示透传原始请求模型。
+	require.Equal(t, "", route.UpstreamModel)
 	require.Equal(t, CompositeRouteEndpointResponses, route.Endpoint)
 	require.Equal(t, 100, route.Priority)
 	require.True(t, route.Enabled)
@@ -1596,6 +1597,29 @@ func TestAdminService_CreateCompositeRoute_NormalizesAndPersists(t *testing.T) {
 	require.Equal(t, route, routeRepo.created)
 }
 
+// TestAdminService_CreateCompositeRoute_ExactEmptyUpstreamBackfillsPublicModel 锁定
+// 保守行为：exact 路由留空 upstream_model 仍回填 public_model（持久化/展示契约不变）。
+func TestAdminService_CreateCompositeRoute_ExactEmptyUpstreamBackfillsPublicModel(t *testing.T) {
+	groupRepo := &groupRepoStubForAdmin{
+		getByID: &Group{ID: 7, Platform: PlatformComposite},
+	}
+	routeRepo := &compositeRouteRepoStubForAdmin{nextID: 99}
+	svc := &adminServiceImpl{groupRepo: groupRepo, compositeRouteRepo: routeRepo}
+
+	route, err := svc.CreateCompositeRoute(context.Background(), 7, CompositeRouteInput{
+		PublicModel:    "openrouter/gpt-5",
+		MatchType:      CompositeRouteMatchExact,
+		TargetPlatform: PlatformOpenAI,
+		Endpoint:       CompositeRouteEndpointResponses,
+		Enabled:        true,
+	})
+
+	require.NoError(t, err)
+	require.NotNil(t, route)
+	require.Equal(t, CompositeRouteMatchExact, route.MatchType)
+	require.Equal(t, "openrouter/gpt-5", route.UpstreamModel)
+}
+
 func TestAdminService_UpdateAndDeleteCompositeRouteRequireRouteOwnership(t *testing.T) {
 	groupRepo := &groupRepoStubForAdmin{
 		getByID: &Group{ID: 7, Platform: PlatformComposite},

backend/internal/service/composite_model_route.go

@@ -118,7 +118,12 @@ func normalizeCompositeRouteInput(input CompositeRouteInput) CompositeRouteInput
 	input.TargetPlatform = strings.TrimSpace(input.TargetPlatform)
 	input.UpstreamModel = strings.TrimSpace(input.UpstreamModel)
 	input.Endpoint = normalizeCompositeRouteEndpoint(input.Endpoint)
-	if input.UpstreamModel == "" {
+	// 仅对 exact 路由把空 upstream_model 回填成 public_model：exact 命中时请求模型
+	// 恒等于 public_model，回填只影响持久化/后台展示，保留原有契约不变。
+	// prefix 路由留空则不回填——Resolve 会回退到具体请求模型，从而透传原始模型
+	// （否则 public=deepseek-v4 的前缀路由会把 deepseek-v4-flash / deepseek-v4-pro
+	// 都塌缩成固定的 deepseek-v4）。显式填写 upstream_model 时任何模式都原样固定转发。
+	if input.UpstreamModel == "" && input.MatchType == CompositeRouteMatchExact {
 		input.UpstreamModel = input.PublicModel
 	}
 	input.Notes = strings.TrimSpace(input.Notes)

backend/internal/service/composite_route_resolver_test.go

@@ -107,6 +107,63 @@ func TestCompositeRouteResolverPrefersEndpointSpecificLongestPrefix(t *testing.T
 	require.Equal(t, int64(2), decision.Route.ID)
 }
 
+// TestCompositeRouteResolverPrefixEmptyUpstreamPassesThroughRequestedModel 验证：
+// 前缀匹配路由留空 upstream_model 时，转发的是具体请求模型（各自原样），而不是
+// 塌缩成 public_model。这是「留空 = 透传原始模型」语义的核心场景。
+func TestCompositeRouteResolverPrefixEmptyUpstreamPassesThroughRequestedModel(t *testing.T) {
+	resolver := NewCompositeRouteResolver(compositeRouteRepoStub{
+		routes: []CompositeModelRoute{
+			{
+				ID:             1,
+				GroupID:        7,
+				PublicModel:    "deepseek-v4",
+				MatchType:      CompositeRouteMatchPrefix,
+				TargetPlatform: PlatformOpenAI,
+				UpstreamModel:  "", // 留空 = 透传
+				Endpoint:       CompositeRouteEndpointAny,
+				Priority:       100,
+				Enabled:        true,
+			},
+		},
+	})
+
+	for _, model := range []string{"deepseek-v4-flash", "deepseek-v4-pro", "deepseek-v4"} {
+		decision, err := resolver.Resolve(context.Background(), 7, model, CompositeRouteEndpointChatCompletions)
+		require.NoError(t, err)
+		require.True(t, decision.Matched, "model %q should match prefix route", model)
+		require.Equal(t, CompositeRouteSourceExplicit, decision.Source)
+		require.Equal(t, PlatformOpenAI, decision.TargetPlatform)
+		require.Equal(t, model, decision.UpstreamModel, "model %q should pass through verbatim", model)
+	}
+}
+
+// TestCompositeRouteResolverPrefixExplicitUpstreamStillFixed 验证：前缀匹配路由显式
+// 填写 upstream_model 时，所有命中请求仍转发同一个固定上游模型（行为不变）。
+func TestCompositeRouteResolverPrefixExplicitUpstreamStillFixed(t *testing.T) {
+	resolver := NewCompositeRouteResolver(compositeRouteRepoStub{
+		routes: []CompositeModelRoute{
+			{
+				ID:             1,
+				GroupID:        7,
+				PublicModel:    "deepseek-v4",
+				MatchType:      CompositeRouteMatchPrefix,
+				TargetPlatform: PlatformOpenAI,
+				UpstreamModel:  "deepseek-chat",
+				Endpoint:       CompositeRouteEndpointAny,
+				Priority:       100,
+				Enabled:        true,
+			},
+		},
+	})
+
+	for _, model := range []string{"deepseek-v4-flash", "deepseek-v4-pro"} {
+		decision, err := resolver.Resolve(context.Background(), 7, model, CompositeRouteEndpointChatCompletions)
+		require.NoError(t, err)
+		require.True(t, decision.Matched)
+		require.Equal(t, "deepseek-chat", decision.UpstreamModel)
+	}
+}
+
 func TestCompositeRouteResolverIgnoresDisabledRoutesAndFallsBackToDetector(t *testing.T) {
 	resolver := NewCompositeRouteResolver(compositeRouteRepoStub{
 		routes: []CompositeModelRoute{