diff --git a/backend/internal/service/gateway_multiplatform_test.go b/backend/internal/service/gateway_multiplatform_test.go
index ec1bf901ad..6568b3f6b4 100644
--- a/backend/internal/service/gateway_multiplatform_test.go
+++ b/backend/internal/service/gateway_multiplatform_test.go
@@ -3515,3 +3515,74 @@ func TestGatewayService_ResolveGatewayGroup_DetectsFallbackCycle(t *testing.T) {
 	require.Nil(t, gotID)
 	require.Contains(t, err.Error(), "fallback group cycle")
 }
+
+func TestModelRoutingAppliesToPlatform(t *testing.T) {
+	for _, tc := range []struct {
+		name           string
+		targetPlatform string
+		groupPlatform  string
+		want           bool
+	}{
+		{"anthropic group", PlatformAnthropic, PlatformAnthropic, true},
+		{"openai group", PlatformOpenAI, PlatformOpenAI, true},
+		{"composite group resolved to anthropic", PlatformAnthropic, PlatformComposite, true},
+		{"composite group resolved to openai", PlatformOpenAI, PlatformComposite, true},
+		{"target platform outside the allowed set", PlatformGemini, PlatformGemini, false},
+		{"composite group resolved outside the allowed set", PlatformGemini, PlatformComposite, false},
+		{"group platform does not match target", PlatformOpenAI, PlatformAnthropic, false},
+		{"empty target platform", "", PlatformOpenAI, false},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			require.Equal(t, tc.want, modelRoutingAppliesToPlatform(tc.targetPlatform, tc.groupPlatform))
+		})
+	}
+}
+
+// Model routing used to be read only for requests resolved to Anthropic, so an
+// OpenAI group's rules were stored and displayed but never honored. Routing an
+// OpenAI request must pick the routed account instead of the group-wide winner.
+func TestGatewayService_SelectAccountForModelWithPlatform_RoutedOpenAIGroup(t *testing.T) {
+	ctx := context.Background()
+	groupID := int64(13)
+	requestedModel := "gpt-6-astra"
+
+	repo := &mockAccountRepoForPlatform{
+		accounts: []Account{
+			// Priority 1 would win any group-wide selection, but it is not routed.
+			{ID: 1, Platform: PlatformOpenAI, Priority: 1, Status: StatusActive, Schedulable: true},
+			{ID: 2, Platform: PlatformOpenAI, Priority: 5, Status: StatusActive, Schedulable: true},
+		},
+		accountsByID: map[int64]*Account{},
+	}
+	for i := range repo.accounts {
+		repo.accountsByID[repo.accounts[i].ID] = &repo.accounts[i]
+	}
+
+	groupRepo := &mockGroupRepoForGateway{
+		groups: map[int64]*Group{
+			groupID: {
+				ID:                  groupID,
+				Name:                "openai-route-group",
+				Platform:            PlatformOpenAI,
+				Status:              StatusActive,
+				Hydrated:            true,
+				ModelRoutingEnabled: true,
+				ModelRouting: map[string][]int64{
+					requestedModel: {2},
+				},
+			},
+		},
+	}
+
+	svc := &GatewayService{
+		accountRepo: repo,
+		cache:       &mockGatewayCacheForPlatform{},
+		cfg:         testConfig(),
+		groupRepo:   groupRepo,
+	}
+
+	acc, err := svc.selectAccountForModelWithPlatform(ctx, &groupID, "", requestedModel, nil, PlatformOpenAI)
+	require.NoError(t, err)
+	require.NotNil(t, acc)
+	require.Equal(t, int64(2), acc.ID, "routed account must win over the higher-priority unrouted one")
+}
diff --git a/backend/internal/service/gateway_scheduling.go b/backend/internal/service/gateway_scheduling.go
index bd05f9e1ca..f5dd160c79 100644
--- a/backend/internal/service/gateway_scheduling.go
+++ b/backend/internal/service/gateway_scheduling.go
@@ -216,7 +216,7 @@ func (s *GatewayService) SelectAccountWithLoadAwareness(ctx context.Context, gro
 		return nil, err
 	}
 	preferOAuth := platform == PlatformGemini
-	if s.debugModelRoutingEnabled() && platform == PlatformAnthropic && requestedModel != "" {
+	if s.debugModelRoutingEnabled() && requestedModel != "" && modelRoutingAppliesToTargetPlatform(platform) {
 		logger.LegacyPrintf("service.gateway", "[ModelRoutingDebug] load-aware enabled: group_id=%v model=%s session=%s platform=%s", derefGroupID(groupID), requestedModel, shortSessionHash(sessionHash), platform)
 	}
 
@@ -250,10 +250,10 @@ func (s *GatewayService) SelectAccountWithLoadAwareness(ctx context.Context, gro
 		return needsUpstreamCheck && s.isUpstreamModelRestrictedByChannel(ctx, *groupID, account, requestedModel)
 	}
 
-	// 获取模型路由配置（anthropic 目标平台；composite 分组按目标平台判断）
+	// 获取模型路由配置（anthropic / openai 目标平台；composite 分组按目标平台判断）
 	var routingAccountIDs []int64
-	if group != nil && requestedModel != "" && platform == PlatformAnthropic &&
-		(group.Platform == PlatformAnthropic || group.Platform == PlatformComposite) {
+	if group != nil && requestedModel != "" &&
+		modelRoutingAppliesToPlatform(platform, group.Platform) {
 		routingAccountIDs = group.GetRoutingAccountIDs(requestedModel)
 		if s.debugModelRoutingEnabled() {
 			logger.LegacyPrintf("service.gateway", "[ModelRoutingDebug] context group routing: group_id=%d model=%s enabled=%v rules=%d matched_ids=%v session=%s sticky_account=%d",
@@ -865,8 +865,35 @@ func (s *GatewayService) ResolveGroupByID(ctx context.Context, groupID int64) (*
 	return s.resolveGroupByID(ctx, groupID)
 }
 
+// modelRoutingAppliesToPlatform 判定模型路由规则是否适用于本次请求。
+//
+// 路由规则的存储与查表（Group.ModelRouting / GetRoutingAccountIDs）本身与平台无关，
+// 早期只有 Anthropic 目标平台会读取它。OpenAI 分组同样存在“同一个公开别名由不同账号
+// 映射到不同上游模型”的故障转移写法，需要显式路由来指定谁是主、谁是备，因此这里把
+// Anthropic 与 OpenAI 一并放行。
+//
+// targetPlatform 是请求解析后的目标平台；groupPlatform 是分组自身的平台。composite
+// 分组不限定自身平台，只要目标平台落在放行集合内即可复用其规则。
+func modelRoutingAppliesToPlatform(targetPlatform, groupPlatform string) bool {
+	if !modelRoutingAppliesToTargetPlatform(targetPlatform) {
+		return false
+	}
+	return groupPlatform == targetPlatform || groupPlatform == PlatformComposite
+}
+
+// modelRoutingAppliesToTargetPlatform 是放行平台集合的唯一定义处：新增平台只改这里。
+// 在只知道目标平台、还没取到分组的位置（调试日志、取分组前的短路）单独判定用。
+func modelRoutingAppliesToTargetPlatform(targetPlatform string) bool {
+	switch targetPlatform {
+	case PlatformAnthropic, PlatformOpenAI:
+		return true
+	default:
+		return false
+	}
+}
+
 func (s *GatewayService) routingAccountIDsForRequest(ctx context.Context, groupID *int64, requestedModel string, platform string) []int64 {
-	if groupID == nil || requestedModel == "" || platform != PlatformAnthropic {
+	if groupID == nil || requestedModel == "" || !modelRoutingAppliesToTargetPlatform(platform) {
 		return nil
 	}
 	group, err := s.resolveGroupByID(ctx, *groupID)
@@ -876,11 +903,11 @@ func (s *GatewayService) routingAccountIDsForRequest(ctx context.Context, groupI
 		}
 		return nil
 	}
-	// Model routing applies only to requests resolved to Anthropic. Composite
-	// groups may still use those rules once their model resolved to Anthropic.
-	if group.Platform != PlatformAnthropic && group.Platform != PlatformComposite {
+	// 路由规则适用于解析到 Anthropic 或 OpenAI 的请求；composite 分组在其模型解析到
+	// 上述平台后同样可以复用这些规则。
+	if !modelRoutingAppliesToPlatform(platform, group.Platform) {
 		if s.debugModelRoutingEnabled() {
-			logger.LegacyPrintf("service.gateway", "[ModelRoutingDebug] skip: non-anthropic group platform: group_id=%d group_platform=%s model=%s", group.ID, group.Platform, requestedModel)
+			logger.LegacyPrintf("service.gateway", "[ModelRoutingDebug] skip: group platform not eligible: group_id=%d group_platform=%s target_platform=%s model=%s", group.ID, group.Platform, platform, requestedModel)
 		}
 		return nil
 	}
diff --git a/backend/internal/service/openai_codex_model_metadata.go b/backend/internal/service/openai_codex_model_metadata.go
index 656919fd8c..63a819e1e0 100644
--- a/backend/internal/service/openai_codex_model_metadata.go
+++ b/backend/internal/service/openai_codex_model_metadata.go
@@ -89,10 +89,23 @@ func accountCodexToolCapabilities(account *Account, modelID string) map[string]j
 	return capabilities
 }
 
+// codexModelRoutingAccountIDs 返回分组显式为该公开别名声明的账号集合。
+//
+// 返回非空表示运营者已经用 model_routing 指明“这个别名由这些账号服务”，此时别名的
+// 归属不再是需要推断的未知量：能力声明只看这些账号，且不再因为它们映射到不同上游而
+// 判定为冲突。返回空表示没有相关规则，保持原有的全量推断与失败即关闭行为。
+func codexModelRoutingAccountIDs(group *Group, modelID string) []int64 {
+	if group == nil {
+		return nil
+	}
+	return group.GetRoutingAccountIDs(strings.TrimSpace(modelID))
+}
+
 func groupCodexModelMetadata(
 	platform string,
 	modelID string,
 	accounts []Account,
+	group *Group,
 	compositeRoutes []CompositeModelRoute,
 	compositeRoutesAvailable bool,
 ) (codexModelMetadataOverride, bool) {
@@ -100,6 +113,9 @@ func groupCodexModelMetadata(
 	if modelID == "" {
 		return codexModelMetadataOverride{}, false
 	}
+	// 显式路由规则本身与平台无关，先取出来供后续两处判定共用。
+	routedAccountIDs := codexModelRoutingAccountIDs(group, modelID)
+	routed := len(routedAccountIDs) > 0
 	upstreamModel := modelID
 	if platform == PlatformComposite {
 		var resolved bool
@@ -110,7 +126,7 @@ func groupCodexModelMetadata(
 			compositeRoutesAvailable,
 		)
 		if !resolved {
-			if codexExplicitModelTargetsConflict(accounts, modelID) {
+			if !routed && codexExplicitModelTargetsConflict(accounts, modelID) {
 				return codexModelMetadataOverride{
 					reasoningConflict:       true,
 					inputModalitiesConflict: true,
@@ -125,14 +141,21 @@ func groupCodexModelMetadata(
 
 	explicitClaims := false
 	if upstreamModel == modelID {
-		for _, account := range accounts {
-			if account.Platform == platform && codexExplicitModelMappingClaims(account, modelID) {
+		for i := range accounts {
+			account := &accounts[i]
+			if routed && !containsInt64(routedAccountIDs, account.ID) {
+				continue
+			}
+			if account.Platform == platform && codexExplicitModelMappingClaims(*account, modelID) {
 				explicitClaims = true
 				break
 			}
 		}
 	}
-	explicitTargetsConflict := explicitClaims && codexExplicitModelTargetsConflictForPlatform(accounts, platform, modelID)
+	// 别名已被显式路由声明时，"多个账号映射到不同上游"是故障转移的正常写法，不是歧义，
+	// 因此不再失败即关闭；能力回落到与单账号无快照时相同的按名推导。
+	explicitTargetsConflict := explicitClaims && !routed &&
+		codexExplicitModelTargetsConflictForPlatform(accounts, platform, modelID)
 	publicAlias := upstreamModel != modelID
 	candidates := make([]UpstreamModelMetadata, 0)
 	missingMetadata := false
@@ -141,6 +164,9 @@ func groupCodexModelMetadata(
 		if account.Platform != platform {
 			continue
 		}
+		if routed && !containsInt64(routedAccountIDs, account.ID) {
+			continue
+		}
 		var lookupModel string
 		if explicitClaims {
 			if !codexExplicitModelMappingClaims(*account, modelID) {
diff --git a/backend/internal/service/openai_codex_model_metadata_test.go b/backend/internal/service/openai_codex_model_metadata_test.go
index 55bc233ed2..616ff88606 100644
--- a/backend/internal/service/openai_codex_model_metadata_test.go
+++ b/backend/internal/service/openai_codex_model_metadata_test.go
@@ -30,7 +30,7 @@ func TestAstraCodexToolCapabilitiesUseAccountScopeAndSharedDeclarations(t *testi
 		{"implemented chat bridge", []Account{bridge}, true},
 	} {
 		t.Run(tt.name, func(t *testing.T) {
-			body, err := buildCodexModelsManifestForAccounts(PlatformOpenAI, []string{"public-astra"}, tt.accounts, nil, true)
+			body, err := buildCodexModelsManifestForAccounts(PlatformOpenAI, []string{"public-astra"}, tt.accounts, nil, nil, true)
 			require.NoError(t, err)
 			model := decodeCodexManifestModels(t, body)[0]
 			require.Equal(t, "public-astra", model["slug"])
@@ -48,7 +48,7 @@ func TestAstraCodexToolCapabilitiesUseAccountScopeAndSharedDeclarations(t *testi
 			"comp_hash": json.RawMessage(`"3000"`), "tool_mode": json.RawMessage("null"), "use_responses_lite": json.RawMessage("false"),
 		}},
 	}})
-	body, err := buildCodexModelsManifestForAccounts(PlatformOpenAI, []string{"public-astra"}, []Account{official, custom}, nil, true)
+	body, err := buildCodexModelsManifestForAccounts(PlatformOpenAI, []string{"public-astra"}, []Account{official, custom}, nil, nil, true)
 	require.NoError(t, err)
 	model := decodeCodexManifestModels(t, body)[0]
 	require.Equal(t, true, model["supports_search_tool"])
@@ -200,7 +200,7 @@ func TestBuildCodexModelsManifestForGroupAdvertisesSearchOnlyForChatBridgeRoutes
 		t.Run(tc.name, func(t *testing.T) {
 			t.Parallel()
 			body, err := buildCodexModelsManifestForAccounts(
-				PlatformOpenAI, []string{"company-coding-model"}, tc.accounts, nil, true,
+				PlatformOpenAI, []string{"company-coding-model"}, tc.accounts, nil, nil, true,
 			)
 			require.NoError(t, err)
 			models := decodeCodexManifestModels(t, body)
@@ -585,7 +585,7 @@ func TestAstraCodexToolCapabilitiesKeepAPIKeyResponsesLiteGuard(t *testing.T) {
 	account.SetUpstreamModelMetadataSnapshot(UpstreamModelMetadataSnapshot{Models: map[string]UpstreamModelMetadata{
 		"gpt-6-astra": {CodexToolCapabilities: map[string]json.RawMessage{"use_responses_lite": json.RawMessage("true")}},
 	}})
-	body, err := buildCodexModelsManifestForAccounts(PlatformOpenAI, []string{"my-astra"}, []Account{account}, nil, true)
+	body, err := buildCodexModelsManifestForAccounts(PlatformOpenAI, []string{"my-astra"}, []Account{account}, nil, nil, true)
 	require.NoError(t, err)
 	require.Equal(t, false, decodeCodexManifestModels(t, body)[0]["use_responses_lite"])
 	body, err = adjustAPIKeyCodexModelsManifest([]byte(`{"models":[{"slug":"my-astra","use_responses_lite":true}]}`), &account)
@@ -593,4 +593,99 @@ func TestAstraCodexToolCapabilitiesKeepAPIKeyResponsesLiteGuard(t *testing.T) {
 	require.Equal(t, false, decodeCodexManifestModels(t, body)[0]["use_responses_lite"])
 }
 
+// Scenario: an OpenAI group keeps a failover account whose mapping points the
+// shared public alias at a different upstream model. Without an explicit routing
+// rule the alias target is ambiguous and capabilities must fail closed; with one,
+// the operator has declared who serves the alias, so the reasoning slider and
+// image input must survive.
+func TestCodexAliasFailoverMappingHonorsModelRouting(t *testing.T) {
+	newAccount := func(id int64, target string, priority int) Account {
+		return Account{
+			ID:       id,
+			Platform: PlatformOpenAI,
+			Type:     AccountTypeAPIKey,
+			Priority: priority,
+			Credentials: map[string]any{
+				"base_url":      "https://relay.example/v1",
+				"model_mapping": map[string]any{"gpt-6-astra": target},
+			},
+		}
+	}
+	// Account 16-alike serves the alias natively; account 1-alike is the failover
+	// and can only reach a different upstream model.
+	primary := newAccount(16, "gpt-6-astra", 0)
+	failover := newAccount(1, "gpt-5.6-sol", 10)
+	accounts := []Account{primary, failover}
+
+	// supported_reasoning_levels entries are {effort, description} objects; the
+	// slider only cares about the effort names.
+	manifestFieldsOf := func(t *testing.T, group *Group) ([]string, any, any) {
+		t.Helper()
+		body, err := buildCodexModelsManifestForAccounts(
+			PlatformOpenAI, []string{"gpt-6-astra"}, accounts, group, nil, true,
+		)
+		require.NoError(t, err)
+		models := decodeCodexManifestModels(t, body)
+		require.Len(t, models, 1)
+		model := models[0]
+		require.Equal(t, "gpt-6-astra", model["slug"])
+		var efforts []string
+		levels, _ := model["supported_reasoning_levels"].([]any)
+		for _, level := range levels {
+			entry, ok := level.(map[string]any)
+			require.True(t, ok, "reasoning level entry must be an object")
+			effort, ok := entry["effort"].(string)
+			require.True(t, ok, "reasoning level entry must carry an effort name")
+			efforts = append(efforts, effort)
+		}
+		return efforts, model["default_reasoning_level"], model["input_modalities"]
+	}
+
+	t.Run("no routing rule still fails closed", func(t *testing.T) {
+		levels, def, modalities := manifestFieldsOf(t, nil)
+		require.Empty(t, levels, "ambiguous alias target must not advertise reasoning levels")
+		require.Nil(t, def)
+		require.Equal(t, []any{"text"}, modalities)
+	})
+
+	t.Run("routing rule resolves the alias", func(t *testing.T) {
+		group := &Group{
+			ID:                  2,
+			Platform:            PlatformOpenAI,
+			ModelRoutingEnabled: true,
+			ModelRouting:        map[string][]int64{"gpt-6-astra": {16, 1}},
+		}
+		levels, def, modalities := manifestFieldsOf(t, group)
+		require.Equal(t,
+			[]string{"low", "medium", "high", "xhigh", "max"},
+			levels,
+			"routed alias must keep a movable reasoning slider",
+		)
+		require.Equal(t, "medium", def)
+		require.Contains(t, modalities, "image")
+	})
+
+	t.Run("routing disabled falls back to failing closed", func(t *testing.T) {
+		group := &Group{
+			ID:                  2,
+			Platform:            PlatformOpenAI,
+			ModelRoutingEnabled: false,
+			ModelRouting:        map[string][]int64{"gpt-6-astra": {16, 1}},
+		}
+		levels, _, _ := manifestFieldsOf(t, group)
+		require.Empty(t, levels, "a disabled routing rule must not resolve the alias")
+	})
+
+	t.Run("routing rule for another alias does not leak", func(t *testing.T) {
+		group := &Group{
+			ID:                  2,
+			Platform:            PlatformOpenAI,
+			ModelRoutingEnabled: true,
+			ModelRouting:        map[string][]int64{"gpt-5.6-sol": {1}},
+		}
+		levels, _, _ := manifestFieldsOf(t, group)
+		require.Empty(t, levels, "unrelated routing rules must not resolve this alias")
+	})
+}
+
 // Scenario: mixed groups prefer capability metadata synced for the routed account.
diff --git a/backend/internal/service/openai_codex_models_service.go b/backend/internal/service/openai_codex_models_service.go
index 742be217ec..c7cbc7c0cc 100644
--- a/backend/internal/service/openai_codex_models_service.go
+++ b/backend/internal/service/openai_codex_models_service.go
@@ -137,6 +137,7 @@ func (s *OpenAIGatewayService) BuildGroupConfiguredCodexModelsManifest(
 		PlatformOpenAI,
 		configuredModels,
 		catalog,
+		group,
 		nil,
 		true,
 	)
@@ -818,6 +819,7 @@ func (s *GatewayService) BuildCodexModelsManifestForGroup(
 		effectivePlatform,
 		modelIDs,
 		catalog,
+		group,
 		compositeRoutes,
 		compositeRoutesAvailable,
 	)
@@ -827,6 +829,7 @@ func buildCodexModelsManifestForAccounts(
 	effectivePlatform string,
 	modelIDs []string,
 	accounts []Account,
+	group *Group,
 	compositeRoutes []CompositeModelRoute,
 	compositeRoutesAvailable bool,
 ) ([]byte, error) {
@@ -864,6 +867,7 @@ func buildCodexModelsManifestForAccounts(
 			effectivePlatform,
 			modelID,
 			accounts,
+			group,
 			compositeRoutes,
 			compositeRoutesAvailable,
 		); ok {