Add invalid-request fallback routing

backend/ent/group.go

@@ -56,6 +56,8 @@ type Group struct {
 	ClaudeCodeOnly bool `json:"claude_code_only,omitempty"`
 	// 非 Claude Code 请求降级使用的分组 ID
 	FallbackGroupID *int64 `json:"fallback_group_id,omitempty"`
+	// 无效请求兜底使用的分组 ID
+	FallbackGroupIDOnInvalidRequest *int64 `json:"fallback_group_id_on_invalid_request,omitempty"`
 	// 模型路由配置：模型模式 -> 优先账号ID列表
 	ModelRouting map[string][]int64 `json:"model_routing,omitempty"`
 	// 是否启用模型路由配置
@@ -172,7 +174,7 @@ func (*Group) scanValues(columns []string) ([]any, error) {
 			values[i] = new(sql.NullBool)
 		case group.FieldRateMultiplier, group.FieldDailyLimitUsd, group.FieldWeeklyLimitUsd, group.FieldMonthlyLimitUsd, group.FieldImagePrice1k, group.FieldImagePrice2k, group.FieldImagePrice4k:
 			values[i] = new(sql.NullFloat64)
-		case group.FieldID, group.FieldDefaultValidityDays, group.FieldFallbackGroupID:
+		case group.FieldID, group.FieldDefaultValidityDays, group.FieldFallbackGroupID, group.FieldFallbackGroupIDOnInvalidRequest:
 			values[i] = new(sql.NullInt64)
 		case group.FieldName, group.FieldDescription, group.FieldStatus, group.FieldPlatform, group.FieldSubscriptionType:
 			values[i] = new(sql.NullString)
@@ -322,6 +324,13 @@ func (_m *Group) assignValues(columns []string, values []any) error {
 				_m.FallbackGroupID = new(int64)
 				*_m.FallbackGroupID = value.Int64
 			}
+		case group.FieldFallbackGroupIDOnInvalidRequest:
+			if value, ok := values[i].(*sql.NullInt64); !ok {
+				return fmt.Errorf("unexpected type %T for field fallback_group_id_on_invalid_request", values[i])
+			} else if value.Valid {
+				_m.FallbackGroupIDOnInvalidRequest = new(int64)
+				*_m.FallbackGroupIDOnInvalidRequest = value.Int64
+			}
 		case group.FieldModelRouting:
 			if value, ok := values[i].(*[]byte); !ok {
 				return fmt.Errorf("unexpected type %T for field model_routing", values[i])
@@ -487,6 +496,11 @@ func (_m *Group) String() string {
 		builder.WriteString(fmt.Sprintf("%v", *v))
 	}
 	builder.WriteString(", ")
+	if v := _m.FallbackGroupIDOnInvalidRequest; v != nil {
+		builder.WriteString("fallback_group_id_on_invalid_request=")
+		builder.WriteString(fmt.Sprintf("%v", *v))
+	}
+	builder.WriteString(", ")
 	builder.WriteString("model_routing=")
 	builder.WriteString(fmt.Sprintf("%v", _m.ModelRouting))
 	builder.WriteString(", ")

backend/ent/group/group.go

@@ -53,6 +53,8 @@ const (
 	FieldClaudeCodeOnly = "claude_code_only"
 	// FieldFallbackGroupID holds the string denoting the fallback_group_id field in the database.
 	FieldFallbackGroupID = "fallback_group_id"
+	// FieldFallbackGroupIDOnInvalidRequest holds the string denoting the fallback_group_id_on_invalid_request field in the database.
+	FieldFallbackGroupIDOnInvalidRequest = "fallback_group_id_on_invalid_request"
 	// FieldModelRouting holds the string denoting the model_routing field in the database.
 	FieldModelRouting = "model_routing"
 	// FieldModelRoutingEnabled holds the string denoting the model_routing_enabled field in the database.
@@ -151,6 +153,7 @@ var Columns = []string{
 	FieldImagePrice4k,
 	FieldClaudeCodeOnly,
 	FieldFallbackGroupID,
+	FieldFallbackGroupIDOnInvalidRequest,
 	FieldModelRouting,
 	FieldModelRoutingEnabled,
 }
@@ -317,6 +320,11 @@ func ByFallbackGroupID(opts ...sql.OrderTermOption) OrderOption {
 	return sql.OrderByField(FieldFallbackGroupID, opts...).ToFunc()
 }
 
+// ByFallbackGroupIDOnInvalidRequest orders the results by the fallback_group_id_on_invalid_request field.
+func ByFallbackGroupIDOnInvalidRequest(opts ...sql.OrderTermOption) OrderOption {
+	return sql.OrderByField(FieldFallbackGroupIDOnInvalidRequest, opts...).ToFunc()
+}
+
 // ByModelRoutingEnabled orders the results by the model_routing_enabled field.
 func ByModelRoutingEnabled(opts ...sql.OrderTermOption) OrderOption {
 	return sql.OrderByField(FieldModelRoutingEnabled, opts...).ToFunc()

backend/ent/group/where.go

@@ -150,6 +150,11 @@ func FallbackGroupID(v int64) predicate.Group {
 	return predicate.Group(sql.FieldEQ(FieldFallbackGroupID, v))
 }
 
+// FallbackGroupIDOnInvalidRequest applies equality check predicate on the "fallback_group_id_on_invalid_request" field. It's identical to FallbackGroupIDOnInvalidRequestEQ.
+func FallbackGroupIDOnInvalidRequest(v int64) predicate.Group {
+	return predicate.Group(sql.FieldEQ(FieldFallbackGroupIDOnInvalidRequest, v))
+}
+
 // ModelRoutingEnabled applies equality check predicate on the "model_routing_enabled" field. It's identical to ModelRoutingEnabledEQ.
 func ModelRoutingEnabled(v bool) predicate.Group {
 	return predicate.Group(sql.FieldEQ(FieldModelRoutingEnabled, v))
@@ -1070,6 +1075,56 @@ func FallbackGroupIDNotNil() predicate.Group {
 	return predicate.Group(sql.FieldNotNull(FieldFallbackGroupID))
 }
 
+// FallbackGroupIDOnInvalidRequestEQ applies the EQ predicate on the "fallback_group_id_on_invalid_request" field.
+func FallbackGroupIDOnInvalidRequestEQ(v int64) predicate.Group {
+	return predicate.Group(sql.FieldEQ(FieldFallbackGroupIDOnInvalidRequest, v))
+}
+
+// FallbackGroupIDOnInvalidRequestNEQ applies the NEQ predicate on the "fallback_group_id_on_invalid_request" field.
+func FallbackGroupIDOnInvalidRequestNEQ(v int64) predicate.Group {
+	return predicate.Group(sql.FieldNEQ(FieldFallbackGroupIDOnInvalidRequest, v))
+}
+
+// FallbackGroupIDOnInvalidRequestIn applies the In predicate on the "fallback_group_id_on_invalid_request" field.
+func FallbackGroupIDOnInvalidRequestIn(vs ...int64) predicate.Group {
+	return predicate.Group(sql.FieldIn(FieldFallbackGroupIDOnInvalidRequest, vs...))
+}
+
+// FallbackGroupIDOnInvalidRequestNotIn applies the NotIn predicate on the "fallback_group_id_on_invalid_request" field.
+func FallbackGroupIDOnInvalidRequestNotIn(vs ...int64) predicate.Group {
+	return predicate.Group(sql.FieldNotIn(FieldFallbackGroupIDOnInvalidRequest, vs...))
+}
+
+// FallbackGroupIDOnInvalidRequestGT applies the GT predicate on the "fallback_group_id_on_invalid_request" field.
+func FallbackGroupIDOnInvalidRequestGT(v int64) predicate.Group {
+	return predicate.Group(sql.FieldGT(FieldFallbackGroupIDOnInvalidRequest, v))
+}
+
+// FallbackGroupIDOnInvalidRequestGTE applies the GTE predicate on the "fallback_group_id_on_invalid_request" field.
+func FallbackGroupIDOnInvalidRequestGTE(v int64) predicate.Group {
+	return predicate.Group(sql.FieldGTE(FieldFallbackGroupIDOnInvalidRequest, v))
+}
+
+// FallbackGroupIDOnInvalidRequestLT applies the LT predicate on the "fallback_group_id_on_invalid_request" field.
+func FallbackGroupIDOnInvalidRequestLT(v int64) predicate.Group {
+	return predicate.Group(sql.FieldLT(FieldFallbackGroupIDOnInvalidRequest, v))
+}
+
+// FallbackGroupIDOnInvalidRequestLTE applies the LTE predicate on the "fallback_group_id_on_invalid_request" field.
+func FallbackGroupIDOnInvalidRequestLTE(v int64) predicate.Group {
+	return predicate.Group(sql.FieldLTE(FieldFallbackGroupIDOnInvalidRequest, v))
+}
+
+// FallbackGroupIDOnInvalidRequestIsNil applies the IsNil predicate on the "fallback_group_id_on_invalid_request" field.
+func FallbackGroupIDOnInvalidRequestIsNil() predicate.Group {
+	return predicate.Group(sql.FieldIsNull(FieldFallbackGroupIDOnInvalidRequest))
+}
+
+// FallbackGroupIDOnInvalidRequestNotNil applies the NotNil predicate on the "fallback_group_id_on_invalid_request" field.
+func FallbackGroupIDOnInvalidRequestNotNil() predicate.Group {
+	return predicate.Group(sql.FieldNotNull(FieldFallbackGroupIDOnInvalidRequest))
+}
+
 // ModelRoutingIsNil applies the IsNil predicate on the "model_routing" field.
 func ModelRoutingIsNil() predicate.Group {
 	return predicate.Group(sql.FieldIsNull(FieldModelRouting))

backend/ent/group_create.go

@@ -286,6 +286,20 @@ func (_c *GroupCreate) SetNillableFallbackGroupID(v *int64) *GroupCreate {
 	return _c
 }
 
+// SetFallbackGroupIDOnInvalidRequest sets the "fallback_group_id_on_invalid_request" field.
+func (_c *GroupCreate) SetFallbackGroupIDOnInvalidRequest(v int64) *GroupCreate {
+	_c.mutation.SetFallbackGroupIDOnInvalidRequest(v)
+	return _c
+}
+
+// SetNillableFallbackGroupIDOnInvalidRequest sets the "fallback_group_id_on_invalid_request" field if the given value is not nil.
+func (_c *GroupCreate) SetNillableFallbackGroupIDOnInvalidRequest(v *int64) *GroupCreate {
+	if v != nil {
+		_c.SetFallbackGroupIDOnInvalidRequest(*v)
+	}
+	return _c
+}
+
 // SetModelRouting sets the "model_routing" field.
 func (_c *GroupCreate) SetModelRouting(v map[string][]int64) *GroupCreate {
 	_c.mutation.SetModelRouting(v)
@@ -640,6 +654,10 @@ func (_c *GroupCreate) createSpec() (*Group, *sqlgraph.CreateSpec) {
 		_spec.SetField(group.FieldFallbackGroupID, field.TypeInt64, value)
 		_node.FallbackGroupID = &value
 	}
+	if value, ok := _c.mutation.FallbackGroupIDOnInvalidRequest(); ok {
+		_spec.SetField(group.FieldFallbackGroupIDOnInvalidRequest, field.TypeInt64, value)
+		_node.FallbackGroupIDOnInvalidRequest = &value
+	}
 	if value, ok := _c.mutation.ModelRouting(); ok {
 		_spec.SetField(group.FieldModelRouting, field.TypeJSON, value)
 		_node.ModelRouting = value
@@ -1128,6 +1146,30 @@ func (u *GroupUpsert) ClearFallbackGroupID() *GroupUpsert {
 	return u
 }
 
+// SetFallbackGroupIDOnInvalidRequest sets the "fallback_group_id_on_invalid_request" field.
+func (u *GroupUpsert) SetFallbackGroupIDOnInvalidRequest(v int64) *GroupUpsert {
+	u.Set(group.FieldFallbackGroupIDOnInvalidRequest, v)
+	return u
+}
+
+// UpdateFallbackGroupIDOnInvalidRequest sets the "fallback_group_id_on_invalid_request" field to the value that was provided on create.
+func (u *GroupUpsert) UpdateFallbackGroupIDOnInvalidRequest() *GroupUpsert {
+	u.SetExcluded(group.FieldFallbackGroupIDOnInvalidRequest)
+	return u
+}
+
+// AddFallbackGroupIDOnInvalidRequest adds v to the "fallback_group_id_on_invalid_request" field.
+func (u *GroupUpsert) AddFallbackGroupIDOnInvalidRequest(v int64) *GroupUpsert {
+	u.Add(group.FieldFallbackGroupIDOnInvalidRequest, v)
+	return u
+}
+
+// ClearFallbackGroupIDOnInvalidRequest clears the value of the "fallback_group_id_on_invalid_request" field.
+func (u *GroupUpsert) ClearFallbackGroupIDOnInvalidRequest() *GroupUpsert {
+	u.SetNull(group.FieldFallbackGroupIDOnInvalidRequest)
+	return u
+}
+
 // SetModelRouting sets the "model_routing" field.
 func (u *GroupUpsert) SetModelRouting(v map[string][]int64) *GroupUpsert {
 	u.Set(group.FieldModelRouting, v)
@@ -1581,6 +1623,34 @@ func (u *GroupUpsertOne) ClearFallbackGroupID() *GroupUpsertOne {
 	})
 }
 
+// SetFallbackGroupIDOnInvalidRequest sets the "fallback_group_id_on_invalid_request" field.
+func (u *GroupUpsertOne) SetFallbackGroupIDOnInvalidRequest(v int64) *GroupUpsertOne {
+	return u.Update(func(s *GroupUpsert) {
+		s.SetFallbackGroupIDOnInvalidRequest(v)
+	})
+}
+
+// AddFallbackGroupIDOnInvalidRequest adds v to the "fallback_group_id_on_invalid_request" field.
+func (u *GroupUpsertOne) AddFallbackGroupIDOnInvalidRequest(v int64) *GroupUpsertOne {
+	return u.Update(func(s *GroupUpsert) {
+		s.AddFallbackGroupIDOnInvalidRequest(v)
+	})
+}
+
+// UpdateFallbackGroupIDOnInvalidRequest sets the "fallback_group_id_on_invalid_request" field to the value that was provided on create.
+func (u *GroupUpsertOne) UpdateFallbackGroupIDOnInvalidRequest() *GroupUpsertOne {
+	return u.Update(func(s *GroupUpsert) {
+		s.UpdateFallbackGroupIDOnInvalidRequest()
+	})
+}
+
+// ClearFallbackGroupIDOnInvalidRequest clears the value of the "fallback_group_id_on_invalid_request" field.
+func (u *GroupUpsertOne) ClearFallbackGroupIDOnInvalidRequest() *GroupUpsertOne {
+	return u.Update(func(s *GroupUpsert) {
+		s.ClearFallbackGroupIDOnInvalidRequest()
+	})
+}
+
 // SetModelRouting sets the "model_routing" field.
 func (u *GroupUpsertOne) SetModelRouting(v map[string][]int64) *GroupUpsertOne {
 	return u.Update(func(s *GroupUpsert) {
@@ -2205,6 +2275,34 @@ func (u *GroupUpsertBulk) ClearFallbackGroupID() *GroupUpsertBulk {
 	})
 }
 
+// SetFallbackGroupIDOnInvalidRequest sets the "fallback_group_id_on_invalid_request" field.
+func (u *GroupUpsertBulk) SetFallbackGroupIDOnInvalidRequest(v int64) *GroupUpsertBulk {
+	return u.Update(func(s *GroupUpsert) {
+		s.SetFallbackGroupIDOnInvalidRequest(v)
+	})
+}
+
+// AddFallbackGroupIDOnInvalidRequest adds v to the "fallback_group_id_on_invalid_request" field.
+func (u *GroupUpsertBulk) AddFallbackGroupIDOnInvalidRequest(v int64) *GroupUpsertBulk {
+	return u.Update(func(s *GroupUpsert) {
+		s.AddFallbackGroupIDOnInvalidRequest(v)
+	})
+}
+
+// UpdateFallbackGroupIDOnInvalidRequest sets the "fallback_group_id_on_invalid_request" field to the value that was provided on create.
+func (u *GroupUpsertBulk) UpdateFallbackGroupIDOnInvalidRequest() *GroupUpsertBulk {
+	return u.Update(func(s *GroupUpsert) {
+		s.UpdateFallbackGroupIDOnInvalidRequest()
+	})
+}
+
+// ClearFallbackGroupIDOnInvalidRequest clears the value of the "fallback_group_id_on_invalid_request" field.
+func (u *GroupUpsertBulk) ClearFallbackGroupIDOnInvalidRequest() *GroupUpsertBulk {
+	return u.Update(func(s *GroupUpsert) {
+		s.ClearFallbackGroupIDOnInvalidRequest()
+	})
+}
+
 // SetModelRouting sets the "model_routing" field.
 func (u *GroupUpsertBulk) SetModelRouting(v map[string][]int64) *GroupUpsertBulk {
 	return u.Update(func(s *GroupUpsert) {

backend/ent/group_update.go

@@ -395,6 +395,33 @@ func (_u *GroupUpdate) ClearFallbackGroupID() *GroupUpdate {
 	return _u
 }
 
+// SetFallbackGroupIDOnInvalidRequest sets the "fallback_group_id_on_invalid_request" field.
+func (_u *GroupUpdate) SetFallbackGroupIDOnInvalidRequest(v int64) *GroupUpdate {
+	_u.mutation.ResetFallbackGroupIDOnInvalidRequest()
+	_u.mutation.SetFallbackGroupIDOnInvalidRequest(v)
+	return _u
+}
+
+// SetNillableFallbackGroupIDOnInvalidRequest sets the "fallback_group_id_on_invalid_request" field if the given value is not nil.
+func (_u *GroupUpdate) SetNillableFallbackGroupIDOnInvalidRequest(v *int64) *GroupUpdate {
+	if v != nil {
+		_u.SetFallbackGroupIDOnInvalidRequest(*v)
+	}
+	return _u
+}
+
+// AddFallbackGroupIDOnInvalidRequest adds value to the "fallback_group_id_on_invalid_request" field.
+func (_u *GroupUpdate) AddFallbackGroupIDOnInvalidRequest(v int64) *GroupUpdate {
+	_u.mutation.AddFallbackGroupIDOnInvalidRequest(v)
+	return _u
+}
+
+// ClearFallbackGroupIDOnInvalidRequest clears the value of the "fallback_group_id_on_invalid_request" field.
+func (_u *GroupUpdate) ClearFallbackGroupIDOnInvalidRequest() *GroupUpdate {
+	_u.mutation.ClearFallbackGroupIDOnInvalidRequest()
+	return _u
+}
+
 // SetModelRouting sets the "model_routing" field.
 func (_u *GroupUpdate) SetModelRouting(v map[string][]int64) *GroupUpdate {
 	_u.mutation.SetModelRouting(v)
@@ -829,6 +856,15 @@ func (_u *GroupUpdate) sqlSave(ctx context.Context) (_node int, err error) {
 	if _u.mutation.FallbackGroupIDCleared() {
 		_spec.ClearField(group.FieldFallbackGroupID, field.TypeInt64)
 	}
+	if value, ok := _u.mutation.FallbackGroupIDOnInvalidRequest(); ok {
+		_spec.SetField(group.FieldFallbackGroupIDOnInvalidRequest, field.TypeInt64, value)
+	}
+	if value, ok := _u.mutation.AddedFallbackGroupIDOnInvalidRequest(); ok {
+		_spec.AddField(group.FieldFallbackGroupIDOnInvalidRequest, field.TypeInt64, value)
+	}
+	if _u.mutation.FallbackGroupIDOnInvalidRequestCleared() {
+		_spec.ClearField(group.FieldFallbackGroupIDOnInvalidRequest, field.TypeInt64)
+	}
 	if value, ok := _u.mutation.ModelRouting(); ok {
 		_spec.SetField(group.FieldModelRouting, field.TypeJSON, value)
 	}
@@ -1513,6 +1549,33 @@ func (_u *GroupUpdateOne) ClearFallbackGroupID() *GroupUpdateOne {
 	return _u
 }
 
+// SetFallbackGroupIDOnInvalidRequest sets the "fallback_group_id_on_invalid_request" field.
+func (_u *GroupUpdateOne) SetFallbackGroupIDOnInvalidRequest(v int64) *GroupUpdateOne {
+	_u.mutation.ResetFallbackGroupIDOnInvalidRequest()
+	_u.mutation.SetFallbackGroupIDOnInvalidRequest(v)
+	return _u
+}
+
+// SetNillableFallbackGroupIDOnInvalidRequest sets the "fallback_group_id_on_invalid_request" field if the given value is not nil.
+func (_u *GroupUpdateOne) SetNillableFallbackGroupIDOnInvalidRequest(v *int64) *GroupUpdateOne {
+	if v != nil {
+		_u.SetFallbackGroupIDOnInvalidRequest(*v)
+	}
+	return _u
+}
+
+// AddFallbackGroupIDOnInvalidRequest adds value to the "fallback_group_id_on_invalid_request" field.
+func (_u *GroupUpdateOne) AddFallbackGroupIDOnInvalidRequest(v int64) *GroupUpdateOne {
+	_u.mutation.AddFallbackGroupIDOnInvalidRequest(v)
+	return _u
+}
+
+// ClearFallbackGroupIDOnInvalidRequest clears the value of the "fallback_group_id_on_invalid_request" field.
+func (_u *GroupUpdateOne) ClearFallbackGroupIDOnInvalidRequest() *GroupUpdateOne {
+	_u.mutation.ClearFallbackGroupIDOnInvalidRequest()
+	return _u
+}
+
 // SetModelRouting sets the "model_routing" field.
 func (_u *GroupUpdateOne) SetModelRouting(v map[string][]int64) *GroupUpdateOne {
 	_u.mutation.SetModelRouting(v)
@@ -1977,6 +2040,15 @@ func (_u *GroupUpdateOne) sqlSave(ctx context.Context) (_node *Group, err error)
 	if _u.mutation.FallbackGroupIDCleared() {
 		_spec.ClearField(group.FieldFallbackGroupID, field.TypeInt64)
 	}
+	if value, ok := _u.mutation.FallbackGroupIDOnInvalidRequest(); ok {
+		_spec.SetField(group.FieldFallbackGroupIDOnInvalidRequest, field.TypeInt64, value)
+	}
+	if value, ok := _u.mutation.AddedFallbackGroupIDOnInvalidRequest(); ok {
+		_spec.AddField(group.FieldFallbackGroupIDOnInvalidRequest, field.TypeInt64, value)
+	}
+	if _u.mutation.FallbackGroupIDOnInvalidRequestCleared() {
+		_spec.ClearField(group.FieldFallbackGroupIDOnInvalidRequest, field.TypeInt64)
+	}
 	if value, ok := _u.mutation.ModelRouting(); ok {
 		_spec.SetField(group.FieldModelRouting, field.TypeJSON, value)
 	}

backend/ent/migrate/schema.go

@@ -226,6 +226,7 @@ var (
 		{Name: "image_price_4k", Type: field.TypeFloat64, Nullable: true, SchemaType: map[string]string{"postgres": "decimal(20,8)"}},
 		{Name: "claude_code_only", Type: field.TypeBool, Default: false},
 		{Name: "fallback_group_id", Type: field.TypeInt64, Nullable: true},
+		{Name: "fallback_group_id_on_invalid_request", Type: field.TypeInt64, Nullable: true},
 		{Name: "model_routing", Type: field.TypeJSON, Nullable: true, SchemaType: map[string]string{"postgres": "jsonb"}},
 		{Name: "model_routing_enabled", Type: field.TypeBool, Default: false},
 	}

backend/ent/mutation.go

@@ -3833,61 +3833,63 @@ func (m *AccountGroupMutation) ResetEdge(name string) error {
 // GroupMutation represents an operation that mutates the Group nodes in the graph.
 type GroupMutation struct {
 	config
-	op                       Op
+	op                                      Op
-	typ                      string
+	typ                                     string
-	id                       *int64
+	id                                      *int64
-	created_at               *time.Time
+	created_at                              *time.Time
-	updated_at               *time.Time
+	updated_at                              *time.Time
-	deleted_at               *time.Time
+	deleted_at                              *time.Time
-	name                     *string
+	name                                    *string
-	description              *string
+	description                             *string
-	rate_multiplier          *float64
+	rate_multiplier                         *float64
-	addrate_multiplier       *float64
+	addrate_multiplier                      *float64
-	is_exclusive             *bool
+	is_exclusive                            *bool
-	status                   *string
+	status                                  *string
-	platform                 *string
+	platform                                *string
-	subscription_type        *string
+	subscription_type                       *string
-	daily_limit_usd          *float64
+	daily_limit_usd                         *float64
-	adddaily_limit_usd       *float64
+	adddaily_limit_usd                      *float64
-	weekly_limit_usd         *float64
+	weekly_limit_usd                        *float64
-	addweekly_limit_usd      *float64
+	addweekly_limit_usd                     *float64
-	monthly_limit_usd        *float64
+	monthly_limit_usd                       *float64
-	addmonthly_limit_usd     *float64
+	addmonthly_limit_usd                    *float64
-	default_validity_days    *int
+	default_validity_days                   *int
-	adddefault_validity_days *int
+	adddefault_validity_days                *int
-	image_price_1k           *float64
+	image_price_1k                          *float64
-	addimage_price_1k        *float64
+	addimage_price_1k                       *float64
-	image_price_2k           *float64
+	image_price_2k                          *float64
-	addimage_price_2k        *float64
+	addimage_price_2k                       *float64
-	image_price_4k           *float64
+	image_price_4k                          *float64
-	addimage_price_4k        *float64
+	addimage_price_4k                       *float64
-	claude_code_only         *bool
+	claude_code_only                        *bool
-	fallback_group_id        *int64
+	fallback_group_id                       *int64
-	addfallback_group_id     *int64
+	addfallback_group_id                    *int64
-	model_routing            *map[string][]int64
+	fallback_group_id_on_invalid_request    *int64
-	model_routing_enabled    *bool
+	addfallback_group_id_on_invalid_request *int64
-	clearedFields            map[string]struct{}
+	model_routing                           *map[string][]int64
-	api_keys                 map[int64]struct{}
+	model_routing_enabled                   *bool
-	removedapi_keys          map[int64]struct{}
+	clearedFields                           map[string]struct{}
-	clearedapi_keys          bool
+	api_keys                                map[int64]struct{}
-	redeem_codes             map[int64]struct{}
+	removedapi_keys                         map[int64]struct{}
-	removedredeem_codes      map[int64]struct{}
+	clearedapi_keys                         bool
-	clearedredeem_codes      bool
+	redeem_codes                            map[int64]struct{}
-	subscriptions            map[int64]struct{}
+	removedredeem_codes                     map[int64]struct{}
-	removedsubscriptions     map[int64]struct{}
+	clearedredeem_codes                     bool
-	clearedsubscriptions     bool
+	subscriptions                           map[int64]struct{}
-	usage_logs               map[int64]struct{}
+	removedsubscriptions                    map[int64]struct{}
-	removedusage_logs        map[int64]struct{}
+	clearedsubscriptions                    bool
-	clearedusage_logs        bool
+	usage_logs                              map[int64]struct{}
-	accounts                 map[int64]struct{}
+	removedusage_logs                       map[int64]struct{}
-	removedaccounts          map[int64]struct{}
+	clearedusage_logs                       bool
-	clearedaccounts          bool
+	accounts                                map[int64]struct{}
-	allowed_users            map[int64]struct{}
+	removedaccounts                         map[int64]struct{}
-	removedallowed_users     map[int64]struct{}
+	clearedaccounts                         bool
-	clearedallowed_users     bool
+	allowed_users                           map[int64]struct{}
-	done                     bool
+	removedallowed_users                    map[int64]struct{}
-	oldValue                 func(context.Context) (*Group, error)
+	clearedallowed_users                    bool
-	predicates               []predicate.Group
+	done                                    bool
+	oldValue                                func(context.Context) (*Group, error)
+	predicates                              []predicate.Group
 }
 
 var _ ent.Mutation = (*GroupMutation)(nil)
@@ -4976,6 +4978,76 @@ func (m *GroupMutation) ResetFallbackGroupID() {
 	delete(m.clearedFields, group.FieldFallbackGroupID)
 }
 
+// SetFallbackGroupIDOnInvalidRequest sets the "fallback_group_id_on_invalid_request" field.
+func (m *GroupMutation) SetFallbackGroupIDOnInvalidRequest(i int64) {
+	m.fallback_group_id_on_invalid_request = &i
+	m.addfallback_group_id_on_invalid_request = nil
+}
+
+// FallbackGroupIDOnInvalidRequest returns the value of the "fallback_group_id_on_invalid_request" field in the mutation.
+func (m *GroupMutation) FallbackGroupIDOnInvalidRequest() (r int64, exists bool) {
+	v := m.fallback_group_id_on_invalid_request
+	if v == nil {
+		return
+	}
+	return *v, true
+}
+
+// OldFallbackGroupIDOnInvalidRequest returns the old "fallback_group_id_on_invalid_request" field's value of the Group entity.
+// If the Group object wasn't provided to the builder, the object is fetched from the database.
+// An error is returned if the mutation operation is not UpdateOne, or the database query fails.
+func (m *GroupMutation) OldFallbackGroupIDOnInvalidRequest(ctx context.Context) (v *int64, err error) {
+	if !m.op.Is(OpUpdateOne) {
+		return v, errors.New("OldFallbackGroupIDOnInvalidRequest is only allowed on UpdateOne operations")
+	}
+	if m.id == nil || m.oldValue == nil {
+		return v, errors.New("OldFallbackGroupIDOnInvalidRequest requires an ID field in the mutation")
+	}
+	oldValue, err := m.oldValue(ctx)
+	if err != nil {
+		return v, fmt.Errorf("querying old value for OldFallbackGroupIDOnInvalidRequest: %w", err)
+	}
+	return oldValue.FallbackGroupIDOnInvalidRequest, nil
+}
+
+// AddFallbackGroupIDOnInvalidRequest adds i to the "fallback_group_id_on_invalid_request" field.
+func (m *GroupMutation) AddFallbackGroupIDOnInvalidRequest(i int64) {
+	if m.addfallback_group_id_on_invalid_request != nil {
+		*m.addfallback_group_id_on_invalid_request += i
+	} else {
+		m.addfallback_group_id_on_invalid_request = &i
+	}
+}
+
+// AddedFallbackGroupIDOnInvalidRequest returns the value that was added to the "fallback_group_id_on_invalid_request" field in this mutation.
+func (m *GroupMutation) AddedFallbackGroupIDOnInvalidRequest() (r int64, exists bool) {
+	v := m.addfallback_group_id_on_invalid_request
+	if v == nil {
+		return
+	}
+	return *v, true
+}
+
+// ClearFallbackGroupIDOnInvalidRequest clears the value of the "fallback_group_id_on_invalid_request" field.
+func (m *GroupMutation) ClearFallbackGroupIDOnInvalidRequest() {
+	m.fallback_group_id_on_invalid_request = nil
+	m.addfallback_group_id_on_invalid_request = nil
+	m.clearedFields[group.FieldFallbackGroupIDOnInvalidRequest] = struct{}{}
+}
+
+// FallbackGroupIDOnInvalidRequestCleared returns if the "fallback_group_id_on_invalid_request" field was cleared in this mutation.
+func (m *GroupMutation) FallbackGroupIDOnInvalidRequestCleared() bool {
+	_, ok := m.clearedFields[group.FieldFallbackGroupIDOnInvalidRequest]
+	return ok
+}
+
+// ResetFallbackGroupIDOnInvalidRequest resets all changes to the "fallback_group_id_on_invalid_request" field.
+func (m *GroupMutation) ResetFallbackGroupIDOnInvalidRequest() {
+	m.fallback_group_id_on_invalid_request = nil
+	m.addfallback_group_id_on_invalid_request = nil
+	delete(m.clearedFields, group.FieldFallbackGroupIDOnInvalidRequest)
+}
+
 // SetModelRouting sets the "model_routing" field.
 func (m *GroupMutation) SetModelRouting(value map[string][]int64) {
 	m.model_routing = &value
@@ -5419,7 +5491,7 @@ func (m *GroupMutation) Type() string {
 // order to get all numeric fields that were incremented/decremented, call
 // AddedFields().
 func (m *GroupMutation) Fields() []string {
-	fields := make([]string, 0, 21)
+	fields := make([]string, 0, 22)
 	if m.created_at != nil {
 		fields = append(fields, group.FieldCreatedAt)
 	}
@@ -5477,6 +5549,9 @@ func (m *GroupMutation) Fields() []string {
 	if m.fallback_group_id != nil {
 		fields = append(fields, group.FieldFallbackGroupID)
 	}
+	if m.fallback_group_id_on_invalid_request != nil {
+		fields = append(fields, group.FieldFallbackGroupIDOnInvalidRequest)
+	}
 	if m.model_routing != nil {
 		fields = append(fields, group.FieldModelRouting)
 	}
@@ -5529,6 +5604,8 @@ func (m *GroupMutation) Field(name string) (ent.Value, bool) {
 		return m.ClaudeCodeOnly()
 	case group.FieldFallbackGroupID:
 		return m.FallbackGroupID()
+	case group.FieldFallbackGroupIDOnInvalidRequest:
+		return m.FallbackGroupIDOnInvalidRequest()
 	case group.FieldModelRouting:
 		return m.ModelRouting()
 	case group.FieldModelRoutingEnabled:
@@ -5580,6 +5657,8 @@ func (m *GroupMutation) OldField(ctx context.Context, name string) (ent.Value, e
 		return m.OldClaudeCodeOnly(ctx)
 	case group.FieldFallbackGroupID:
 		return m.OldFallbackGroupID(ctx)
+	case group.FieldFallbackGroupIDOnInvalidRequest:
+		return m.OldFallbackGroupIDOnInvalidRequest(ctx)
 	case group.FieldModelRouting:
 		return m.OldModelRouting(ctx)
 	case group.FieldModelRoutingEnabled:
@@ -5726,6 +5805,13 @@ func (m *GroupMutation) SetField(name string, value ent.Value) error {
 		}
 		m.SetFallbackGroupID(v)
 		return nil
+	case group.FieldFallbackGroupIDOnInvalidRequest:
+		v, ok := value.(int64)
+		if !ok {
+			return fmt.Errorf("unexpected type %T for field %s", value, name)
+		}
+		m.SetFallbackGroupIDOnInvalidRequest(v)
+		return nil
 	case group.FieldModelRouting:
 		v, ok := value.(map[string][]int64)
 		if !ok {
@@ -5775,6 +5861,9 @@ func (m *GroupMutation) AddedFields() []string {
 	if m.addfallback_group_id != nil {
 		fields = append(fields, group.FieldFallbackGroupID)
 	}
+	if m.addfallback_group_id_on_invalid_request != nil {
+		fields = append(fields, group.FieldFallbackGroupIDOnInvalidRequest)
+	}
 	return fields
 }
 
@@ -5801,6 +5890,8 @@ func (m *GroupMutation) AddedField(name string) (ent.Value, bool) {
 		return m.AddedImagePrice4k()
 	case group.FieldFallbackGroupID:
 		return m.AddedFallbackGroupID()
+	case group.FieldFallbackGroupIDOnInvalidRequest:
+		return m.AddedFallbackGroupIDOnInvalidRequest()
 	}
 	return nil, false
 }
@@ -5873,6 +5964,13 @@ func (m *GroupMutation) AddField(name string, value ent.Value) error {
 		}
 		m.AddFallbackGroupID(v)
 		return nil
+	case group.FieldFallbackGroupIDOnInvalidRequest:
+		v, ok := value.(int64)
+		if !ok {
+			return fmt.Errorf("unexpected type %T for field %s", value, name)
+		}
+		m.AddFallbackGroupIDOnInvalidRequest(v)
+		return nil
 	}
 	return fmt.Errorf("unknown Group numeric field %s", name)
 }
@@ -5908,6 +6006,9 @@ func (m *GroupMutation) ClearedFields() []string {
 	if m.FieldCleared(group.FieldFallbackGroupID) {
 		fields = append(fields, group.FieldFallbackGroupID)
 	}
+	if m.FieldCleared(group.FieldFallbackGroupIDOnInvalidRequest) {
+		fields = append(fields, group.FieldFallbackGroupIDOnInvalidRequest)
+	}
 	if m.FieldCleared(group.FieldModelRouting) {
 		fields = append(fields, group.FieldModelRouting)
 	}
@@ -5952,6 +6053,9 @@ func (m *GroupMutation) ClearField(name string) error {
 	case group.FieldFallbackGroupID:
 		m.ClearFallbackGroupID()
 		return nil
+	case group.FieldFallbackGroupIDOnInvalidRequest:
+		m.ClearFallbackGroupIDOnInvalidRequest()
+		return nil
 	case group.FieldModelRouting:
 		m.ClearModelRouting()
 		return nil
@@ -6020,6 +6124,9 @@ func (m *GroupMutation) ResetField(name string) error {
 	case group.FieldFallbackGroupID:
 		m.ResetFallbackGroupID()
 		return nil
+	case group.FieldFallbackGroupIDOnInvalidRequest:
+		m.ResetFallbackGroupIDOnInvalidRequest()
+		return nil
 	case group.FieldModelRouting:
 		m.ResetModelRouting()
 		return nil

backend/ent/runtime/runtime.go

@@ -281,7 +281,7 @@ func init() {
 	// group.DefaultClaudeCodeOnly holds the default value on creation for the claude_code_only field.
 	group.DefaultClaudeCodeOnly = groupDescClaudeCodeOnly.Default.(bool)
 	// groupDescModelRoutingEnabled is the schema descriptor for model_routing_enabled field.
-	groupDescModelRoutingEnabled := groupFields[17].Descriptor()
+	groupDescModelRoutingEnabled := groupFields[18].Descriptor()
 	// group.DefaultModelRoutingEnabled holds the default value on creation for the model_routing_enabled field.
 	group.DefaultModelRoutingEnabled = groupDescModelRoutingEnabled.Default.(bool)
 	promocodeFields := schema.PromoCode{}.Fields()

backend/ent/schema/group.go

@@ -95,6 +95,10 @@ func (Group) Fields() []ent.Field {
 			Optional().
 			Nillable().
 			Comment("非 Claude Code 请求降级使用的分组 ID"),
+		field.Int64("fallback_group_id_on_invalid_request").
+			Optional().
+			Nillable().
+			Comment("无效请求兜底使用的分组 ID"),
 
 		// 模型路由配置 (added by migration 040)
 		field.JSON("model_routing", map[string][]int64{}).

backend/internal/handler/admin/group_handler.go

@@ -35,11 +35,12 @@ type CreateGroupRequest struct {
 	WeeklyLimitUSD   *float64 `json:"weekly_limit_usd"`
 	MonthlyLimitUSD  *float64 `json:"monthly_limit_usd"`
 	// 图片生成计费配置（antigravity 和 gemini 平台使用，负数表示清除配置）
-	ImagePrice1K    *float64 `json:"image_price_1k"`
+	ImagePrice1K                    *float64 `json:"image_price_1k"`
-	ImagePrice2K    *float64 `json:"image_price_2k"`
+	ImagePrice2K                    *float64 `json:"image_price_2k"`
-	ImagePrice4K    *float64 `json:"image_price_4k"`
+	ImagePrice4K                    *float64 `json:"image_price_4k"`
-	ClaudeCodeOnly  bool     `json:"claude_code_only"`
+	ClaudeCodeOnly                  bool     `json:"claude_code_only"`
-	FallbackGroupID *int64   `json:"fallback_group_id"`
+	FallbackGroupID                 *int64   `json:"fallback_group_id"`
+	FallbackGroupIDOnInvalidRequest *int64   `json:"fallback_group_id_on_invalid_request"`
 	// 模型路由配置（仅 anthropic 平台使用）
 	ModelRouting        map[string][]int64 `json:"model_routing"`
 	ModelRoutingEnabled bool               `json:"model_routing_enabled"`
@@ -58,11 +59,12 @@ type UpdateGroupRequest struct {
 	WeeklyLimitUSD   *float64 `json:"weekly_limit_usd"`
 	MonthlyLimitUSD  *float64 `json:"monthly_limit_usd"`
 	// 图片生成计费配置（antigravity 和 gemini 平台使用，负数表示清除配置）
-	ImagePrice1K    *float64 `json:"image_price_1k"`
+	ImagePrice1K                    *float64 `json:"image_price_1k"`
-	ImagePrice2K    *float64 `json:"image_price_2k"`
+	ImagePrice2K                    *float64 `json:"image_price_2k"`
-	ImagePrice4K    *float64 `json:"image_price_4k"`
+	ImagePrice4K                    *float64 `json:"image_price_4k"`
-	ClaudeCodeOnly  *bool    `json:"claude_code_only"`
+	ClaudeCodeOnly                  *bool    `json:"claude_code_only"`
-	FallbackGroupID *int64   `json:"fallback_group_id"`
+	FallbackGroupID                 *int64   `json:"fallback_group_id"`
+	FallbackGroupIDOnInvalidRequest *int64   `json:"fallback_group_id_on_invalid_request"`
 	// 模型路由配置（仅 anthropic 平台使用）
 	ModelRouting        map[string][]int64 `json:"model_routing"`
 	ModelRoutingEnabled *bool              `json:"model_routing_enabled"`
@@ -155,22 +157,23 @@ func (h *GroupHandler) Create(c *gin.Context) {
 	}
 
 	group, err := h.adminService.CreateGroup(c.Request.Context(), &service.CreateGroupInput{
-		Name:                req.Name,
+		Name:                            req.Name,
-		Description:         req.Description,
+		Description:                     req.Description,
-		Platform:            req.Platform,
+		Platform:                        req.Platform,
-		RateMultiplier:      req.RateMultiplier,
+		RateMultiplier:                  req.RateMultiplier,
-		IsExclusive:         req.IsExclusive,
+		IsExclusive:                     req.IsExclusive,
-		SubscriptionType:    req.SubscriptionType,
+		SubscriptionType:                req.SubscriptionType,
-		DailyLimitUSD:       req.DailyLimitUSD,
+		DailyLimitUSD:                   req.DailyLimitUSD,
-		WeeklyLimitUSD:      req.WeeklyLimitUSD,
+		WeeklyLimitUSD:                  req.WeeklyLimitUSD,
-		MonthlyLimitUSD:     req.MonthlyLimitUSD,
+		MonthlyLimitUSD:                 req.MonthlyLimitUSD,
-		ImagePrice1K:        req.ImagePrice1K,
+		ImagePrice1K:                    req.ImagePrice1K,
-		ImagePrice2K:        req.ImagePrice2K,
+		ImagePrice2K:                    req.ImagePrice2K,
-		ImagePrice4K:        req.ImagePrice4K,
+		ImagePrice4K:                    req.ImagePrice4K,
-		ClaudeCodeOnly:      req.ClaudeCodeOnly,
+		ClaudeCodeOnly:                  req.ClaudeCodeOnly,
-		FallbackGroupID:     req.FallbackGroupID,
+		FallbackGroupID:                 req.FallbackGroupID,
-		ModelRouting:        req.ModelRouting,
+		FallbackGroupIDOnInvalidRequest: req.FallbackGroupIDOnInvalidRequest,
-		ModelRoutingEnabled: req.ModelRoutingEnabled,
+		ModelRouting:                    req.ModelRouting,
+		ModelRoutingEnabled:             req.ModelRoutingEnabled,
 	})
 	if err != nil {
 		response.ErrorFrom(c, err)
@@ -196,23 +199,24 @@ func (h *GroupHandler) Update(c *gin.Context) {
 	}
 
 	group, err := h.adminService.UpdateGroup(c.Request.Context(), groupID, &service.UpdateGroupInput{
-		Name:                req.Name,
+		Name:                            req.Name,
-		Description:         req.Description,
+		Description:                     req.Description,
-		Platform:            req.Platform,
+		Platform:                        req.Platform,
-		RateMultiplier:      req.RateMultiplier,
+		RateMultiplier:                  req.RateMultiplier,
-		IsExclusive:         req.IsExclusive,
+		IsExclusive:                     req.IsExclusive,
-		Status:              req.Status,
+		Status:                          req.Status,
-		SubscriptionType:    req.SubscriptionType,
+		SubscriptionType:                req.SubscriptionType,
-		DailyLimitUSD:       req.DailyLimitUSD,
+		DailyLimitUSD:                   req.DailyLimitUSD,
-		WeeklyLimitUSD:      req.WeeklyLimitUSD,
+		WeeklyLimitUSD:                  req.WeeklyLimitUSD,
-		MonthlyLimitUSD:     req.MonthlyLimitUSD,
+		MonthlyLimitUSD:                 req.MonthlyLimitUSD,
-		ImagePrice1K:        req.ImagePrice1K,
+		ImagePrice1K:                    req.ImagePrice1K,
-		ImagePrice2K:        req.ImagePrice2K,
+		ImagePrice2K:                    req.ImagePrice2K,
-		ImagePrice4K:        req.ImagePrice4K,
+		ImagePrice4K:                    req.ImagePrice4K,
-		ClaudeCodeOnly:      req.ClaudeCodeOnly,
+		ClaudeCodeOnly:                  req.ClaudeCodeOnly,
-		FallbackGroupID:     req.FallbackGroupID,
+		FallbackGroupID:                 req.FallbackGroupID,
-		ModelRouting:        req.ModelRouting,
+		FallbackGroupIDOnInvalidRequest: req.FallbackGroupIDOnInvalidRequest,
-		ModelRoutingEnabled: req.ModelRoutingEnabled,
+		ModelRouting:                    req.ModelRouting,
+		ModelRoutingEnabled:             req.ModelRoutingEnabled,
 	})
 	if err != nil {
 		response.ErrorFrom(c, err)

backend/internal/handler/dto/mappers.go

@@ -73,27 +73,28 @@ func GroupFromServiceShallow(g *service.Group) *Group {
 		return nil
 	}
 	return &Group{
-		ID:                  g.ID,
+		ID:                              g.ID,
-		Name:                g.Name,
+		Name:                            g.Name,
-		Description:         g.Description,
+		Description:                     g.Description,
-		Platform:            g.Platform,
+		Platform:                        g.Platform,
-		RateMultiplier:      g.RateMultiplier,
+		RateMultiplier:                  g.RateMultiplier,
-		IsExclusive:         g.IsExclusive,
+		IsExclusive:                     g.IsExclusive,
-		Status:              g.Status,
+		Status:                          g.Status,
-		SubscriptionType:    g.SubscriptionType,
+		SubscriptionType:                g.SubscriptionType,
-		DailyLimitUSD:       g.DailyLimitUSD,
+		DailyLimitUSD:                   g.DailyLimitUSD,
-		WeeklyLimitUSD:      g.WeeklyLimitUSD,
+		WeeklyLimitUSD:                  g.WeeklyLimitUSD,
-		MonthlyLimitUSD:     g.MonthlyLimitUSD,
+		MonthlyLimitUSD:                 g.MonthlyLimitUSD,
-		ImagePrice1K:        g.ImagePrice1K,
+		ImagePrice1K:                    g.ImagePrice1K,
-		ImagePrice2K:        g.ImagePrice2K,
+		ImagePrice2K:                    g.ImagePrice2K,
-		ImagePrice4K:        g.ImagePrice4K,
+		ImagePrice4K:                    g.ImagePrice4K,
-		ClaudeCodeOnly:      g.ClaudeCodeOnly,
+		ClaudeCodeOnly:                  g.ClaudeCodeOnly,
-		FallbackGroupID:     g.FallbackGroupID,
+		FallbackGroupID:                 g.FallbackGroupID,
-		ModelRouting:        g.ModelRouting,
+		FallbackGroupIDOnInvalidRequest: g.FallbackGroupIDOnInvalidRequest,
-		ModelRoutingEnabled: g.ModelRoutingEnabled,
+		ModelRouting:                    g.ModelRouting,
-		CreatedAt:           g.CreatedAt,
+		ModelRoutingEnabled:             g.ModelRoutingEnabled,
-		UpdatedAt:           g.UpdatedAt,
+		CreatedAt:                       g.CreatedAt,
-		AccountCount:        g.AccountCount,
+		UpdatedAt:                       g.UpdatedAt,
+		AccountCount:                    g.AccountCount,
 	}
 }
 

backend/internal/handler/dto/types.go

@@ -57,6 +57,8 @@ type Group struct {
 	// Claude Code 客户端限制
 	ClaudeCodeOnly  bool   `json:"claude_code_only"`
 	FallbackGroupID *int64 `json:"fallback_group_id"`
+	// 无效请求兜底分组
+	FallbackGroupIDOnInvalidRequest *int64 `json:"fallback_group_id_on_invalid_request"`
 
 	// 模型路由配置（仅 anthropic 平台使用）
 	ModelRouting        map[string][]int64 `json:"model_routing"`

backend/internal/handler/gateway_handler.go

@@ -14,6 +14,7 @@ import (
 	"github.com/Wei-Shaw/sub2api/internal/config"
 	"github.com/Wei-Shaw/sub2api/internal/pkg/antigravity"
 	"github.com/Wei-Shaw/sub2api/internal/pkg/claude"
+	"github.com/Wei-Shaw/sub2api/internal/pkg/ctxkey"
 	pkgerrors "github.com/Wei-Shaw/sub2api/internal/pkg/errors"
 	"github.com/Wei-Shaw/sub2api/internal/pkg/ip"
 	"github.com/Wei-Shaw/sub2api/internal/pkg/openai"
@@ -325,136 +326,186 @@ func (h *GatewayHandler) Messages(c *gin.Context) {
 		}
 	}
 
-	maxAccountSwitches := h.maxAccountSwitches
+	currentAPIKey := apiKey
-	switchCount := 0
+	currentSubscription := subscription
-	failedAccountIDs := make(map[int64]struct{})
+	var fallbackGroupID *int64
-	lastFailoverStatus := 0
+	if apiKey.Group != nil {
+		fallbackGroupID = apiKey.Group.FallbackGroupIDOnInvalidRequest
+	}
+	fallbackUsed := false
 
 	for {
-		// 选择支持该模型的账号
+		maxAccountSwitches := h.maxAccountSwitches
-		selection, err := h.gatewayService.SelectAccountWithLoadAwareness(c.Request.Context(), apiKey.GroupID, sessionKey, reqModel, failedAccountIDs, parsedReq.MetadataUserID)
+		switchCount := 0
-		if err != nil {
+		failedAccountIDs := make(map[int64]struct{})
-			if len(failedAccountIDs) == 0 {
+		lastFailoverStatus := 0
-				h.handleStreamingAwareError(c, http.StatusServiceUnavailable, "api_error", "No available accounts: "+err.Error(), streamStarted)
+		retryWithFallback := false
-				return
-			}
-			h.handleFailoverExhausted(c, lastFailoverStatus, streamStarted)
-			return
-		}
-		account := selection.Account
-		setOpsSelectedAccount(c, account.ID)
 
-		// 检查预热请求拦截（在账号选择后、转发前检查）
+		for {
-		if account.IsInterceptWarmupEnabled() && isWarmupRequest(body) {
+			// 选择支持该模型的账号
-			if selection.Acquired && selection.ReleaseFunc != nil {
+			selection, err := h.gatewayService.SelectAccountWithLoadAwareness(c.Request.Context(), currentAPIKey.GroupID, sessionKey, reqModel, failedAccountIDs, parsedReq.MetadataUserID)
-				selection.ReleaseFunc()
-			}
-			if reqStream {
-				sendMockWarmupStream(c, reqModel)
-			} else {
-				sendMockWarmupResponse(c, reqModel)
-			}
-			return
-		}
-
-		// 3. 获取账号并发槽位
-		accountReleaseFunc := selection.ReleaseFunc
-		if !selection.Acquired {
-			if selection.WaitPlan == nil {
-				h.handleStreamingAwareError(c, http.StatusServiceUnavailable, "api_error", "No available accounts", streamStarted)
-				return
-			}
-			accountWaitCounted := false
-			canWait, err := h.concurrencyHelper.IncrementAccountWaitCount(c.Request.Context(), account.ID, selection.WaitPlan.MaxWaiting)
 			if err != nil {
-				log.Printf("Increment account wait count failed: %v", err)
+				if len(failedAccountIDs) == 0 {
-			} else if !canWait {
+					h.handleStreamingAwareError(c, http.StatusServiceUnavailable, "api_error", "No available accounts: "+err.Error(), streamStarted)
-				log.Printf("Account wait queue full: account=%d", account.ID)
-				h.handleStreamingAwareError(c, http.StatusTooManyRequests, "rate_limit_error", "Too many pending requests, please retry later", streamStarted)
-				return
-			}
-			if err == nil && canWait {
-				accountWaitCounted = true
-			}
-			defer func() {
-				if accountWaitCounted {
-					h.concurrencyHelper.DecrementAccountWaitCount(c.Request.Context(), account.ID)
-				}
-			}()
-
-			accountReleaseFunc, err = h.concurrencyHelper.AcquireAccountSlotWithWaitTimeout(
-				c,
-				account.ID,
-				selection.WaitPlan.MaxConcurrency,
-				selection.WaitPlan.Timeout,
-				reqStream,
-				&streamStarted,
-			)
-			if err != nil {
-				log.Printf("Account concurrency acquire failed: %v", err)
-				h.handleConcurrencyError(c, err, "account", streamStarted)
-				return
-			}
-			if accountWaitCounted {
-				h.concurrencyHelper.DecrementAccountWaitCount(c.Request.Context(), account.ID)
-				accountWaitCounted = false
-			}
-			if err := h.gatewayService.BindStickySession(c.Request.Context(), apiKey.GroupID, sessionKey, account.ID); err != nil {
-				log.Printf("Bind sticky session failed: %v", err)
-			}
-		}
-		// 账号槽位/等待计数需要在超时或断开时安全回收
-		accountReleaseFunc = wrapReleaseOnDone(c.Request.Context(), accountReleaseFunc)
-
-		// 转发请求 - 根据账号平台分流
-		var result *service.ForwardResult
-		if account.Platform == service.PlatformAntigravity {
-			result, err = h.antigravityGatewayService.Forward(c.Request.Context(), c, account, body)
-		} else {
-			result, err = h.gatewayService.Forward(c.Request.Context(), c, account, parsedReq)
-		}
-		if accountReleaseFunc != nil {
-			accountReleaseFunc()
-		}
-		if err != nil {
-			var failoverErr *service.UpstreamFailoverError
-			if errors.As(err, &failoverErr) {
-				failedAccountIDs[account.ID] = struct{}{}
-				lastFailoverStatus = failoverErr.StatusCode
-				if switchCount >= maxAccountSwitches {
-					h.handleFailoverExhausted(c, lastFailoverStatus, streamStarted)
 					return
 				}
-				switchCount++
+				h.handleFailoverExhausted(c, lastFailoverStatus, streamStarted)
-				log.Printf("Account %d: upstream error %d, switching account %d/%d", account.ID, failoverErr.StatusCode, switchCount, maxAccountSwitches)
+				return
-				continue
 			}
-			// 错误响应已在Forward中处理，这里只记录日志
+			account := selection.Account
-			log.Printf("Account %d: Forward request failed: %v", account.ID, err)
+			setOpsSelectedAccount(c, account.ID)
+
+			// 检查预热请求拦截（在账号选择后、转发前检查）
+			if account.IsInterceptWarmupEnabled() && isWarmupRequest(body) {
+				if selection.Acquired && selection.ReleaseFunc != nil {
+					selection.ReleaseFunc()
+				}
+				if reqStream {
+					sendMockWarmupStream(c, reqModel)
+				} else {
+					sendMockWarmupResponse(c, reqModel)
+				}
+				return
+			}
+
+			// 3. 获取账号并发槽位
+			accountReleaseFunc := selection.ReleaseFunc
+			if !selection.Acquired {
+				if selection.WaitPlan == nil {
+					h.handleStreamingAwareError(c, http.StatusServiceUnavailable, "api_error", "No available accounts", streamStarted)
+					return
+				}
+				accountWaitCounted := false
+				canWait, err := h.concurrencyHelper.IncrementAccountWaitCount(c.Request.Context(), account.ID, selection.WaitPlan.MaxWaiting)
+				if err != nil {
+					log.Printf("Increment account wait count failed: %v", err)
+				} else if !canWait {
+					log.Printf("Account wait queue full: account=%d", account.ID)
+					h.handleStreamingAwareError(c, http.StatusTooManyRequests, "rate_limit_error", "Too many pending requests, please retry later", streamStarted)
+					return
+				}
+				if err == nil && canWait {
+					accountWaitCounted = true
+				}
+				defer func() {
+					if accountWaitCounted {
+						h.concurrencyHelper.DecrementAccountWaitCount(c.Request.Context(), account.ID)
+					}
+				}()
+
+				accountReleaseFunc, err = h.concurrencyHelper.AcquireAccountSlotWithWaitTimeout(
+					c,
+					account.ID,
+					selection.WaitPlan.MaxConcurrency,
+					selection.WaitPlan.Timeout,
+					reqStream,
+					&streamStarted,
+				)
+				if err != nil {
+					log.Printf("Account concurrency acquire failed: %v", err)
+					h.handleConcurrencyError(c, err, "account", streamStarted)
+					return
+				}
+				if accountWaitCounted {
+					h.concurrencyHelper.DecrementAccountWaitCount(c.Request.Context(), account.ID)
+					accountWaitCounted = false
+				}
+				if err := h.gatewayService.BindStickySession(c.Request.Context(), currentAPIKey.GroupID, sessionKey, account.ID); err != nil {
+					log.Printf("Bind sticky session failed: %v", err)
+				}
+			}
+			// 账号槽位/等待计数需要在超时或断开时安全回收
+			accountReleaseFunc = wrapReleaseOnDone(c.Request.Context(), accountReleaseFunc)
+
+			// 转发请求 - 根据账号平台分流
+			var result *service.ForwardResult
+			if account.Platform == service.PlatformAntigravity {
+				result, err = h.antigravityGatewayService.Forward(c.Request.Context(), c, account, body)
+			} else {
+				result, err = h.gatewayService.Forward(c.Request.Context(), c, account, parsedReq)
+			}
+			if accountReleaseFunc != nil {
+				accountReleaseFunc()
+			}
+			if err != nil {
+				var promptTooLongErr *service.PromptTooLongError
+				if errors.As(err, &promptTooLongErr) {
+					log.Printf("Prompt too long from antigravity: group=%d fallback_group_id=%v fallback_used=%v", currentAPIKey.GroupID, fallbackGroupID, fallbackUsed)
+					if !fallbackUsed && fallbackGroupID != nil && *fallbackGroupID > 0 {
+						fallbackGroup, err := h.gatewayService.ResolveGroupByID(c.Request.Context(), *fallbackGroupID)
+						if err != nil {
+							log.Printf("Resolve fallback group failed: %v", err)
+							_ = h.antigravityGatewayService.WriteMappedClaudeError(c, account, promptTooLongErr.StatusCode, promptTooLongErr.RequestID, promptTooLongErr.Body)
+							return
+						}
+						if fallbackGroup.Platform != service.PlatformAnthropic ||
+							fallbackGroup.SubscriptionType == service.SubscriptionTypeSubscription ||
+							fallbackGroup.FallbackGroupIDOnInvalidRequest != nil {
+							log.Printf("Fallback group invalid: group=%d platform=%s subscription=%s", fallbackGroup.ID, fallbackGroup.Platform, fallbackGroup.SubscriptionType)
+							_ = h.antigravityGatewayService.WriteMappedClaudeError(c, account, promptTooLongErr.StatusCode, promptTooLongErr.RequestID, promptTooLongErr.Body)
+							return
+						}
+						fallbackAPIKey := cloneAPIKeyWithGroup(apiKey, fallbackGroup)
+						if err := h.billingCacheService.CheckBillingEligibility(c.Request.Context(), fallbackAPIKey.User, fallbackAPIKey, fallbackGroup, nil); err != nil {
+							status, code, message := billingErrorDetails(err)
+							h.handleStreamingAwareError(c, status, code, message, streamStarted)
+							return
+						}
+						// 兜底重试按“直接请求兜底分组”处理：清除强制平台，允许按分组平台调度
+						ctx := context.WithValue(c.Request.Context(), ctxkey.ForcePlatform, "")
+						c.Request = c.Request.WithContext(ctx)
+						currentAPIKey = fallbackAPIKey
+						currentSubscription = nil
+						fallbackUsed = true
+						retryWithFallback = true
+						break
+					}
+					_ = h.antigravityGatewayService.WriteMappedClaudeError(c, account, promptTooLongErr.StatusCode, promptTooLongErr.RequestID, promptTooLongErr.Body)
+					return
+				}
+				var failoverErr *service.UpstreamFailoverError
+				if errors.As(err, &failoverErr) {
+					failedAccountIDs[account.ID] = struct{}{}
+					lastFailoverStatus = failoverErr.StatusCode
+					if switchCount >= maxAccountSwitches {
+						h.handleFailoverExhausted(c, lastFailoverStatus, streamStarted)
+						return
+					}
+					switchCount++
+					log.Printf("Account %d: upstream error %d, switching account %d/%d", account.ID, failoverErr.StatusCode, switchCount, maxAccountSwitches)
+					continue
+				}
+				// 错误响应已在Forward中处理，这里只记录日志
+				log.Printf("Account %d: Forward request failed: %v", account.ID, err)
+				return
+			}
+
+			// 捕获请求信息（用于异步记录，避免在 goroutine 中访问 gin.Context）
+			userAgent := c.GetHeader("User-Agent")
+			clientIP := ip.GetClientIP(c)
+
+			// 异步记录使用量（subscription已在函数开头获取）
+			go func(result *service.ForwardResult, usedAccount *service.Account, ua, clientIP string) {
+				ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+				defer cancel()
+				if err := h.gatewayService.RecordUsage(ctx, &service.RecordUsageInput{
+					Result:       result,
+					APIKey:       currentAPIKey,
+					User:         currentAPIKey.User,
+					Account:      usedAccount,
+					Subscription: currentSubscription,
+					UserAgent:    ua,
+					IPAddress:    clientIP,
+				}); err != nil {
+					log.Printf("Record usage failed: %v", err)
+				}
+			}(result, account, userAgent, clientIP)
 			return
 		}
 
-		// 捕获请求信息（用于异步记录，避免在 goroutine 中访问 gin.Context）
+		if !retryWithFallback {
-		userAgent := c.GetHeader("User-Agent")
+			return
-		clientIP := ip.GetClientIP(c)
+		}
-
-		// 异步记录使用量（subscription已在函数开头获取）
-		go func(result *service.ForwardResult, usedAccount *service.Account, ua, clientIP string) {
-			ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
-			defer cancel()
-			if err := h.gatewayService.RecordUsage(ctx, &service.RecordUsageInput{
-				Result:       result,
-				APIKey:       apiKey,
-				User:         apiKey.User,
-				Account:      usedAccount,
-				Subscription: subscription,
-				UserAgent:    ua,
-				IPAddress:    clientIP,
-			}); err != nil {
-				log.Printf("Record usage failed: %v", err)
-			}
-		}(result, account, userAgent, clientIP)
-		return
 	}
 }
 
@@ -518,6 +569,17 @@ func (h *GatewayHandler) AntigravityModels(c *gin.Context) {
 	})
 }
 
+func cloneAPIKeyWithGroup(apiKey *service.APIKey, group *service.Group) *service.APIKey {
+	if apiKey == nil || group == nil {
+		return apiKey
+	}
+	cloned := *apiKey
+	groupID := group.ID
+	cloned.GroupID = &groupID
+	cloned.Group = group
+	return &cloned
+}
+
 // Usage handles getting account balance for CC Switch integration
 // GET /v1/usage
 func (h *GatewayHandler) Usage(c *gin.Context) {

backend/internal/repository/api_key_repo.go

@@ -136,6 +136,7 @@ func (r *apiKeyRepository) GetByKeyForAuth(ctx context.Context, key string) (*se
 				group.FieldImagePrice4k,
 				group.FieldClaudeCodeOnly,
 				group.FieldFallbackGroupID,
+				group.FieldFallbackGroupIDOnInvalidRequest,
 				group.FieldModelRoutingEnabled,
 				group.FieldModelRouting,
 			)
@@ -406,28 +407,29 @@ func groupEntityToService(g *dbent.Group) *service.Group {
 		return nil
 	}
 	return &service.Group{
-		ID:                  g.ID,
+		ID:                              g.ID,
-		Name:                g.Name,
+		Name:                            g.Name,
-		Description:         derefString(g.Description),
+		Description:                     derefString(g.Description),
-		Platform:            g.Platform,
+		Platform:                        g.Platform,
-		RateMultiplier:      g.RateMultiplier,
+		RateMultiplier:                  g.RateMultiplier,
-		IsExclusive:         g.IsExclusive,
+		IsExclusive:                     g.IsExclusive,
-		Status:              g.Status,
+		Status:                          g.Status,
-		Hydrated:            true,
+		Hydrated:                        true,
-		SubscriptionType:    g.SubscriptionType,
+		SubscriptionType:                g.SubscriptionType,
-		DailyLimitUSD:       g.DailyLimitUsd,
+		DailyLimitUSD:                   g.DailyLimitUsd,
-		WeeklyLimitUSD:      g.WeeklyLimitUsd,
+		WeeklyLimitUSD:                  g.WeeklyLimitUsd,
-		MonthlyLimitUSD:     g.MonthlyLimitUsd,
+		MonthlyLimitUSD:                 g.MonthlyLimitUsd,
-		ImagePrice1K:        g.ImagePrice1k,
+		ImagePrice1K:                    g.ImagePrice1k,
-		ImagePrice2K:        g.ImagePrice2k,
+		ImagePrice2K:                    g.ImagePrice2k,
-		ImagePrice4K:        g.ImagePrice4k,
+		ImagePrice4K:                    g.ImagePrice4k,
-		DefaultValidityDays: g.DefaultValidityDays,
+		DefaultValidityDays:             g.DefaultValidityDays,
-		ClaudeCodeOnly:      g.ClaudeCodeOnly,
+		ClaudeCodeOnly:                  g.ClaudeCodeOnly,
-		FallbackGroupID:     g.FallbackGroupID,
+		FallbackGroupID:                 g.FallbackGroupID,
-		ModelRouting:        g.ModelRouting,
+		FallbackGroupIDOnInvalidRequest: g.FallbackGroupIDOnInvalidRequest,
-		ModelRoutingEnabled: g.ModelRoutingEnabled,
+		ModelRouting:                    g.ModelRouting,
-		CreatedAt:           g.CreatedAt,
+		ModelRoutingEnabled:             g.ModelRoutingEnabled,
-		UpdatedAt:           g.UpdatedAt,
+		CreatedAt:                       g.CreatedAt,
+		UpdatedAt:                       g.UpdatedAt,
 	}
 }
 

backend/internal/repository/group_repo.go

@@ -50,6 +50,7 @@ func (r *groupRepository) Create(ctx context.Context, groupIn *service.Group) er
 		SetDefaultValidityDays(groupIn.DefaultValidityDays).
 		SetClaudeCodeOnly(groupIn.ClaudeCodeOnly).
 		SetNillableFallbackGroupID(groupIn.FallbackGroupID).
+		SetNillableFallbackGroupIDOnInvalidRequest(groupIn.FallbackGroupIDOnInvalidRequest).
 		SetModelRoutingEnabled(groupIn.ModelRoutingEnabled)
 
 	// 设置模型路由配置
@@ -116,6 +117,12 @@ func (r *groupRepository) Update(ctx context.Context, groupIn *service.Group) er
 	} else {
 		builder = builder.ClearFallbackGroupID()
 	}
+	// 处理 FallbackGroupIDOnInvalidRequest：nil 时清除，否则设置
+	if groupIn.FallbackGroupIDOnInvalidRequest != nil {
+		builder = builder.SetFallbackGroupIDOnInvalidRequest(*groupIn.FallbackGroupIDOnInvalidRequest)
+	} else {
+		builder = builder.ClearFallbackGroupIDOnInvalidRequest()
+	}
 
 	// 处理 ModelRouting：nil 时清除，否则设置
 	if groupIn.ModelRouting != nil {

backend/internal/service/admin_service.go

@@ -108,6 +108,8 @@ type CreateGroupInput struct {
 	ImagePrice4K    *float64
 	ClaudeCodeOnly  bool   // 仅允许 Claude Code 客户端
 	FallbackGroupID *int64 // 降级分组 ID
+	// 无效请求兜底分组 ID（仅 anthropic 平台使用）
+	FallbackGroupIDOnInvalidRequest *int64
 	// 模型路由配置（仅 anthropic 平台使用）
 	ModelRouting        map[string][]int64
 	ModelRoutingEnabled bool // 是否启用模型路由
@@ -130,6 +132,8 @@ type UpdateGroupInput struct {
 	ImagePrice4K    *float64
 	ClaudeCodeOnly  *bool  // 仅允许 Claude Code 客户端
 	FallbackGroupID *int64 // 降级分组 ID
+	// 无效请求兜底分组 ID（仅 anthropic 平台使用）
+	FallbackGroupIDOnInvalidRequest *int64
 	// 模型路由配置（仅 anthropic 平台使用）
 	ModelRouting        map[string][]int64
 	ModelRoutingEnabled *bool // 是否启用模型路由
@@ -572,24 +576,35 @@ func (s *adminServiceImpl) CreateGroup(ctx context.Context, input *CreateGroupIn
 			return nil, err
 		}
 	}
+	fallbackOnInvalidRequest := input.FallbackGroupIDOnInvalidRequest
+	if fallbackOnInvalidRequest != nil && *fallbackOnInvalidRequest <= 0 {
+		fallbackOnInvalidRequest = nil
+	}
+	// 校验无效请求兜底分组
+	if fallbackOnInvalidRequest != nil {
+		if err := s.validateFallbackGroupOnInvalidRequest(ctx, 0, platform, subscriptionType, *fallbackOnInvalidRequest); err != nil {
+			return nil, err
+		}
+	}
 
 	group := &Group{
-		Name:             input.Name,
+		Name:                            input.Name,
-		Description:      input.Description,
+		Description:                     input.Description,
-		Platform:         platform,
+		Platform:                        platform,
-		RateMultiplier:   input.RateMultiplier,
+		RateMultiplier:                  input.RateMultiplier,
-		IsExclusive:      input.IsExclusive,
+		IsExclusive:                     input.IsExclusive,
-		Status:           StatusActive,
+		Status:                          StatusActive,
-		SubscriptionType: subscriptionType,
+		SubscriptionType:                subscriptionType,
-		DailyLimitUSD:    dailyLimit,
+		DailyLimitUSD:                   dailyLimit,
-		WeeklyLimitUSD:   weeklyLimit,
+		WeeklyLimitUSD:                  weeklyLimit,
-		MonthlyLimitUSD:  monthlyLimit,
+		MonthlyLimitUSD:                 monthlyLimit,
-		ImagePrice1K:     imagePrice1K,
+		ImagePrice1K:                    imagePrice1K,
-		ImagePrice2K:     imagePrice2K,
+		ImagePrice2K:                    imagePrice2K,
-		ImagePrice4K:     imagePrice4K,
+		ImagePrice4K:                    imagePrice4K,
-		ClaudeCodeOnly:   input.ClaudeCodeOnly,
+		ClaudeCodeOnly:                  input.ClaudeCodeOnly,
-		FallbackGroupID:  input.FallbackGroupID,
+		FallbackGroupID:                 input.FallbackGroupID,
-		ModelRouting:     input.ModelRouting,
+		FallbackGroupIDOnInvalidRequest: fallbackOnInvalidRequest,
+		ModelRouting:                    input.ModelRouting,
 	}
 	if err := s.groupRepo.Create(ctx, group); err != nil {
 		return nil, err
@@ -651,6 +666,37 @@ func (s *adminServiceImpl) validateFallbackGroup(ctx context.Context, currentGro
 	}
 }
 
+// validateFallbackGroupOnInvalidRequest 校验无效请求兜底分组的有效性
+// currentGroupID: 当前分组 ID（新建时为 0）
+// platform/subscriptionType: 当前分组的有效平台/订阅类型
+// fallbackGroupID: 兜底分组 ID
+func (s *adminServiceImpl) validateFallbackGroupOnInvalidRequest(ctx context.Context, currentGroupID int64, platform, subscriptionType string, fallbackGroupID int64) error {
+	if platform != PlatformAnthropic && platform != PlatformAntigravity {
+		return fmt.Errorf("invalid request fallback only supported for anthropic or antigravity groups")
+	}
+	if subscriptionType == SubscriptionTypeSubscription {
+		return fmt.Errorf("subscription groups cannot set invalid request fallback")
+	}
+	if currentGroupID > 0 && currentGroupID == fallbackGroupID {
+		return fmt.Errorf("cannot set self as invalid request fallback group")
+	}
+
+	fallbackGroup, err := s.groupRepo.GetByIDLite(ctx, fallbackGroupID)
+	if err != nil {
+		return fmt.Errorf("fallback group not found: %w", err)
+	}
+	if fallbackGroup.Platform != PlatformAnthropic {
+		return fmt.Errorf("fallback group must be anthropic platform")
+	}
+	if fallbackGroup.SubscriptionType == SubscriptionTypeSubscription {
+		return fmt.Errorf("fallback group cannot be subscription type")
+	}
+	if fallbackGroup.FallbackGroupIDOnInvalidRequest != nil {
+		return fmt.Errorf("fallback group cannot have invalid request fallback configured")
+	}
+	return nil
+}
+
 func (s *adminServiceImpl) UpdateGroup(ctx context.Context, id int64, input *UpdateGroupInput) (*Group, error) {
 	group, err := s.groupRepo.GetByID(ctx, id)
 	if err != nil {
@@ -717,6 +763,20 @@ func (s *adminServiceImpl) UpdateGroup(ctx context.Context, id int64, input *Upd
 			group.FallbackGroupID = nil
 		}
 	}
+	fallbackOnInvalidRequest := group.FallbackGroupIDOnInvalidRequest
+	if input.FallbackGroupIDOnInvalidRequest != nil {
+		if *input.FallbackGroupIDOnInvalidRequest > 0 {
+			fallbackOnInvalidRequest = input.FallbackGroupIDOnInvalidRequest
+		} else {
+			fallbackOnInvalidRequest = nil
+		}
+	}
+	if fallbackOnInvalidRequest != nil {
+		if err := s.validateFallbackGroupOnInvalidRequest(ctx, id, group.Platform, group.SubscriptionType, *fallbackOnInvalidRequest); err != nil {
+			return nil, err
+		}
+	}
+	group.FallbackGroupIDOnInvalidRequest = fallbackOnInvalidRequest
 
 	// 模型路由配置
 	if input.ModelRouting != nil {

backend/internal/service/admin_service_group_test.go

@@ -378,3 +378,374 @@ func (s *groupRepoStubForFallbackCycle) GetAccountCount(_ context.Context, _ int
 func (s *groupRepoStubForFallbackCycle) DeleteAccountGroupsByGroupID(_ context.Context, _ int64) (int64, error) {
 	panic("unexpected DeleteAccountGroupsByGroupID call")
 }
+
+type groupRepoStubForInvalidRequestFallback struct {
+	groups  map[int64]*Group
+	created *Group
+	updated *Group
+}
+
+func (s *groupRepoStubForInvalidRequestFallback) Create(_ context.Context, g *Group) error {
+	s.created = g
+	return nil
+}
+
+func (s *groupRepoStubForInvalidRequestFallback) Update(_ context.Context, g *Group) error {
+	s.updated = g
+	return nil
+}
+
+func (s *groupRepoStubForInvalidRequestFallback) GetByID(ctx context.Context, id int64) (*Group, error) {
+	return s.GetByIDLite(ctx, id)
+}
+
+func (s *groupRepoStubForInvalidRequestFallback) GetByIDLite(_ context.Context, id int64) (*Group, error) {
+	if g, ok := s.groups[id]; ok {
+		return g, nil
+	}
+	return nil, ErrGroupNotFound
+}
+
+func (s *groupRepoStubForInvalidRequestFallback) Delete(_ context.Context, _ int64) error {
+	panic("unexpected Delete call")
+}
+
+func (s *groupRepoStubForInvalidRequestFallback) DeleteCascade(_ context.Context, _ int64) ([]int64, error) {
+	panic("unexpected DeleteCascade call")
+}
+
+func (s *groupRepoStubForInvalidRequestFallback) List(_ context.Context, _ pagination.PaginationParams) ([]Group, *pagination.PaginationResult, error) {
+	panic("unexpected List call")
+}
+
+func (s *groupRepoStubForInvalidRequestFallback) ListWithFilters(_ context.Context, _ pagination.PaginationParams, _, _, _ string, _ *bool) ([]Group, *pagination.PaginationResult, error) {
+	panic("unexpected ListWithFilters call")
+}
+
+func (s *groupRepoStubForInvalidRequestFallback) ListActive(_ context.Context) ([]Group, error) {
+	panic("unexpected ListActive call")
+}
+
+func (s *groupRepoStubForInvalidRequestFallback) ListActiveByPlatform(_ context.Context, _ string) ([]Group, error) {
+	panic("unexpected ListActiveByPlatform call")
+}
+
+func (s *groupRepoStubForInvalidRequestFallback) ExistsByName(_ context.Context, _ string) (bool, error) {
+	panic("unexpected ExistsByName call")
+}
+
+func (s *groupRepoStubForInvalidRequestFallback) GetAccountCount(_ context.Context, _ int64) (int64, error) {
+	panic("unexpected GetAccountCount call")
+}
+
+func (s *groupRepoStubForInvalidRequestFallback) DeleteAccountGroupsByGroupID(_ context.Context, _ int64) (int64, error) {
+	panic("unexpected DeleteAccountGroupsByGroupID call")
+}
+
+func TestAdminService_CreateGroup_InvalidRequestFallbackRejectsUnsupportedPlatform(t *testing.T) {
+	fallbackID := int64(10)
+	repo := &groupRepoStubForInvalidRequestFallback{
+		groups: map[int64]*Group{
+			fallbackID: {ID: fallbackID, Platform: PlatformAnthropic, SubscriptionType: SubscriptionTypeStandard},
+		},
+	}
+	svc := &adminServiceImpl{groupRepo: repo}
+
+	_, err := svc.CreateGroup(context.Background(), &CreateGroupInput{
+		Name:                            "g1",
+		Platform:                        PlatformOpenAI,
+		SubscriptionType:                SubscriptionTypeStandard,
+		FallbackGroupIDOnInvalidRequest: &fallbackID,
+	})
+	require.Error(t, err)
+	require.Contains(t, err.Error(), "invalid request fallback only supported for anthropic or antigravity groups")
+	require.Nil(t, repo.created)
+}
+
+func TestAdminService_CreateGroup_InvalidRequestFallbackRejectsSubscription(t *testing.T) {
+	fallbackID := int64(10)
+	repo := &groupRepoStubForInvalidRequestFallback{
+		groups: map[int64]*Group{
+			fallbackID: {ID: fallbackID, Platform: PlatformAnthropic, SubscriptionType: SubscriptionTypeStandard},
+		},
+	}
+	svc := &adminServiceImpl{groupRepo: repo}
+
+	_, err := svc.CreateGroup(context.Background(), &CreateGroupInput{
+		Name:                            "g1",
+		Platform:                        PlatformAnthropic,
+		SubscriptionType:                SubscriptionTypeSubscription,
+		FallbackGroupIDOnInvalidRequest: &fallbackID,
+	})
+	require.Error(t, err)
+	require.Contains(t, err.Error(), "subscription groups cannot set invalid request fallback")
+	require.Nil(t, repo.created)
+}
+
+func TestAdminService_CreateGroup_InvalidRequestFallbackRejectsFallbackGroup(t *testing.T) {
+	tests := []struct {
+		name        string
+		fallback    *Group
+		wantMessage string
+	}{
+		{
+			name:        "openai_target",
+			fallback:    &Group{ID: 10, Platform: PlatformOpenAI, SubscriptionType: SubscriptionTypeStandard},
+			wantMessage: "fallback group must be anthropic platform",
+		},
+		{
+			name:        "antigravity_target",
+			fallback:    &Group{ID: 10, Platform: PlatformAntigravity, SubscriptionType: SubscriptionTypeStandard},
+			wantMessage: "fallback group must be anthropic platform",
+		},
+		{
+			name:        "subscription_group",
+			fallback:    &Group{ID: 10, Platform: PlatformAnthropic, SubscriptionType: SubscriptionTypeSubscription},
+			wantMessage: "fallback group cannot be subscription type",
+		},
+		{
+			name: "nested_fallback",
+			fallback: &Group{
+				ID:                              10,
+				Platform:                        PlatformAnthropic,
+				SubscriptionType:                SubscriptionTypeStandard,
+				FallbackGroupIDOnInvalidRequest: func() *int64 { v := int64(99); return &v }(),
+			},
+			wantMessage: "fallback group cannot have invalid request fallback configured",
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			fallbackID := tc.fallback.ID
+			repo := &groupRepoStubForInvalidRequestFallback{
+				groups: map[int64]*Group{
+					fallbackID: tc.fallback,
+				},
+			}
+			svc := &adminServiceImpl{groupRepo: repo}
+
+			_, err := svc.CreateGroup(context.Background(), &CreateGroupInput{
+				Name:                            "g1",
+				Platform:                        PlatformAnthropic,
+				SubscriptionType:                SubscriptionTypeStandard,
+				FallbackGroupIDOnInvalidRequest: &fallbackID,
+			})
+			require.Error(t, err)
+			require.Contains(t, err.Error(), tc.wantMessage)
+			require.Nil(t, repo.created)
+		})
+	}
+}
+
+func TestAdminService_CreateGroup_InvalidRequestFallbackNotFound(t *testing.T) {
+	fallbackID := int64(10)
+	repo := &groupRepoStubForInvalidRequestFallback{}
+	svc := &adminServiceImpl{groupRepo: repo}
+
+	_, err := svc.CreateGroup(context.Background(), &CreateGroupInput{
+		Name:                            "g1",
+		Platform:                        PlatformAnthropic,
+		SubscriptionType:                SubscriptionTypeStandard,
+		FallbackGroupIDOnInvalidRequest: &fallbackID,
+	})
+	require.Error(t, err)
+	require.Contains(t, err.Error(), "fallback group not found")
+	require.Nil(t, repo.created)
+}
+
+func TestAdminService_CreateGroup_InvalidRequestFallbackAllowsAntigravity(t *testing.T) {
+	fallbackID := int64(10)
+	repo := &groupRepoStubForInvalidRequestFallback{
+		groups: map[int64]*Group{
+			fallbackID: {ID: fallbackID, Platform: PlatformAnthropic, SubscriptionType: SubscriptionTypeStandard},
+		},
+	}
+	svc := &adminServiceImpl{groupRepo: repo}
+
+	group, err := svc.CreateGroup(context.Background(), &CreateGroupInput{
+		Name:                            "g1",
+		Platform:                        PlatformAntigravity,
+		SubscriptionType:                SubscriptionTypeStandard,
+		FallbackGroupIDOnInvalidRequest: &fallbackID,
+	})
+	require.NoError(t, err)
+	require.NotNil(t, group)
+	require.NotNil(t, repo.created)
+	require.Equal(t, fallbackID, *repo.created.FallbackGroupIDOnInvalidRequest)
+}
+
+func TestAdminService_CreateGroup_InvalidRequestFallbackClearsOnZero(t *testing.T) {
+	zero := int64(0)
+	repo := &groupRepoStubForInvalidRequestFallback{}
+	svc := &adminServiceImpl{groupRepo: repo}
+
+	group, err := svc.CreateGroup(context.Background(), &CreateGroupInput{
+		Name:                            "g1",
+		Platform:                        PlatformAnthropic,
+		SubscriptionType:                SubscriptionTypeStandard,
+		FallbackGroupIDOnInvalidRequest: &zero,
+	})
+	require.NoError(t, err)
+	require.NotNil(t, group)
+	require.NotNil(t, repo.created)
+	require.Nil(t, repo.created.FallbackGroupIDOnInvalidRequest)
+}
+
+func TestAdminService_UpdateGroup_InvalidRequestFallbackPlatformMismatch(t *testing.T) {
+	fallbackID := int64(10)
+	existing := &Group{
+		ID:                              1,
+		Name:                            "g1",
+		Platform:                        PlatformAnthropic,
+		SubscriptionType:                SubscriptionTypeStandard,
+		Status:                          StatusActive,
+		FallbackGroupIDOnInvalidRequest: &fallbackID,
+	}
+	repo := &groupRepoStubForInvalidRequestFallback{
+		groups: map[int64]*Group{
+			existing.ID: existing,
+			fallbackID:  {ID: fallbackID, Platform: PlatformAnthropic, SubscriptionType: SubscriptionTypeStandard},
+		},
+	}
+	svc := &adminServiceImpl{groupRepo: repo}
+
+	_, err := svc.UpdateGroup(context.Background(), existing.ID, &UpdateGroupInput{
+		Platform: PlatformOpenAI,
+	})
+	require.Error(t, err)
+	require.Contains(t, err.Error(), "invalid request fallback only supported for anthropic or antigravity groups")
+	require.Nil(t, repo.updated)
+}
+
+func TestAdminService_UpdateGroup_InvalidRequestFallbackSubscriptionMismatch(t *testing.T) {
+	fallbackID := int64(10)
+	existing := &Group{
+		ID:                              1,
+		Name:                            "g1",
+		Platform:                        PlatformAnthropic,
+		SubscriptionType:                SubscriptionTypeStandard,
+		Status:                          StatusActive,
+		FallbackGroupIDOnInvalidRequest: &fallbackID,
+	}
+	repo := &groupRepoStubForInvalidRequestFallback{
+		groups: map[int64]*Group{
+			existing.ID: existing,
+			fallbackID:  {ID: fallbackID, Platform: PlatformAnthropic, SubscriptionType: SubscriptionTypeStandard},
+		},
+	}
+	svc := &adminServiceImpl{groupRepo: repo}
+
+	_, err := svc.UpdateGroup(context.Background(), existing.ID, &UpdateGroupInput{
+		SubscriptionType: SubscriptionTypeSubscription,
+	})
+	require.Error(t, err)
+	require.Contains(t, err.Error(), "subscription groups cannot set invalid request fallback")
+	require.Nil(t, repo.updated)
+}
+
+func TestAdminService_UpdateGroup_InvalidRequestFallbackClearsOnZero(t *testing.T) {
+	fallbackID := int64(10)
+	existing := &Group{
+		ID:                              1,
+		Name:                            "g1",
+		Platform:                        PlatformAnthropic,
+		SubscriptionType:                SubscriptionTypeStandard,
+		Status:                          StatusActive,
+		FallbackGroupIDOnInvalidRequest: &fallbackID,
+	}
+	repo := &groupRepoStubForInvalidRequestFallback{
+		groups: map[int64]*Group{
+			existing.ID: existing,
+			fallbackID:  {ID: fallbackID, Platform: PlatformAnthropic, SubscriptionType: SubscriptionTypeStandard},
+		},
+	}
+	svc := &adminServiceImpl{groupRepo: repo}
+
+	clear := int64(0)
+	group, err := svc.UpdateGroup(context.Background(), existing.ID, &UpdateGroupInput{
+		Platform:                        PlatformOpenAI,
+		FallbackGroupIDOnInvalidRequest: &clear,
+	})
+	require.NoError(t, err)
+	require.NotNil(t, group)
+	require.NotNil(t, repo.updated)
+	require.Nil(t, repo.updated.FallbackGroupIDOnInvalidRequest)
+}
+
+func TestAdminService_UpdateGroup_InvalidRequestFallbackRejectsFallbackGroup(t *testing.T) {
+	fallbackID := int64(10)
+	existing := &Group{
+		ID:               1,
+		Name:             "g1",
+		Platform:         PlatformAnthropic,
+		SubscriptionType: SubscriptionTypeStandard,
+		Status:           StatusActive,
+	}
+	repo := &groupRepoStubForInvalidRequestFallback{
+		groups: map[int64]*Group{
+			existing.ID: existing,
+			fallbackID:  {ID: fallbackID, Platform: PlatformAnthropic, SubscriptionType: SubscriptionTypeSubscription},
+		},
+	}
+	svc := &adminServiceImpl{groupRepo: repo}
+
+	_, err := svc.UpdateGroup(context.Background(), existing.ID, &UpdateGroupInput{
+		FallbackGroupIDOnInvalidRequest: &fallbackID,
+	})
+	require.Error(t, err)
+	require.Contains(t, err.Error(), "fallback group cannot be subscription type")
+	require.Nil(t, repo.updated)
+}
+
+func TestAdminService_UpdateGroup_InvalidRequestFallbackSetSuccess(t *testing.T) {
+	fallbackID := int64(10)
+	existing := &Group{
+		ID:               1,
+		Name:             "g1",
+		Platform:         PlatformAnthropic,
+		SubscriptionType: SubscriptionTypeStandard,
+		Status:           StatusActive,
+	}
+	repo := &groupRepoStubForInvalidRequestFallback{
+		groups: map[int64]*Group{
+			existing.ID: existing,
+			fallbackID:  {ID: fallbackID, Platform: PlatformAnthropic, SubscriptionType: SubscriptionTypeStandard},
+		},
+	}
+	svc := &adminServiceImpl{groupRepo: repo}
+
+	group, err := svc.UpdateGroup(context.Background(), existing.ID, &UpdateGroupInput{
+		FallbackGroupIDOnInvalidRequest: &fallbackID,
+	})
+	require.NoError(t, err)
+	require.NotNil(t, group)
+	require.NotNil(t, repo.updated)
+	require.Equal(t, fallbackID, *repo.updated.FallbackGroupIDOnInvalidRequest)
+}
+
+func TestAdminService_UpdateGroup_InvalidRequestFallbackAllowsAntigravity(t *testing.T) {
+	fallbackID := int64(10)
+	existing := &Group{
+		ID:               1,
+		Name:             "g1",
+		Platform:         PlatformAntigravity,
+		SubscriptionType: SubscriptionTypeStandard,
+		Status:           StatusActive,
+	}
+	repo := &groupRepoStubForInvalidRequestFallback{
+		groups: map[int64]*Group{
+			existing.ID: existing,
+			fallbackID:  {ID: fallbackID, Platform: PlatformAnthropic, SubscriptionType: SubscriptionTypeStandard},
+		},
+	}
+	svc := &adminServiceImpl{groupRepo: repo}
+
+	group, err := svc.UpdateGroup(context.Background(), existing.ID, &UpdateGroupInput{
+		FallbackGroupIDOnInvalidRequest: &fallbackID,
+	})
+	require.NoError(t, err)
+	require.NotNil(t, group)
+	require.NotNil(t, repo.updated)
+	require.Equal(t, fallbackID, *repo.updated.FallbackGroupIDOnInvalidRequest)
+}

backend/internal/service/antigravity_gateway_service.go

@@ -62,6 +62,17 @@ type antigravityRetryLoopResult struct {
 	resp *http.Response
 }
 
+// PromptTooLongError 表示上游明确返回 prompt too long
+type PromptTooLongError struct {
+	StatusCode int
+	RequestID  string
+	Body       []byte
+}
+
+func (e *PromptTooLongError) Error() string {
+	return fmt.Sprintf("prompt too long: status=%d", e.StatusCode)
+}
+
 // antigravityRetryLoop 执行带 URL fallback 的重试循环
 func antigravityRetryLoop(p antigravityRetryLoopParams) (*antigravityRetryLoopResult, error) {
 	availableURLs := antigravity.DefaultURLAvailability.GetAvailableURLs()
@@ -930,6 +941,39 @@ func (s *AntigravityGatewayService) Forward(ctx context.Context, c *gin.Context,
 
 		// 处理错误响应（重试后仍失败或不触发重试）
 		if resp.StatusCode >= 400 {
+			if resp.StatusCode == http.StatusBadRequest {
+				upstreamMsg := strings.TrimSpace(extractAntigravityErrorMessage(respBody))
+				upstreamMsg = sanitizeUpstreamErrorMessage(upstreamMsg)
+				log.Printf("%s status=400 prompt_too_long=%v upstream_message=%q request_id=%s body=%s", prefix, isPromptTooLongError(respBody), upstreamMsg, resp.Header.Get("x-request-id"), truncateForLog(respBody, 500))
+			}
+			if resp.StatusCode == http.StatusBadRequest && isPromptTooLongError(respBody) {
+				upstreamMsg := strings.TrimSpace(extractAntigravityErrorMessage(respBody))
+				upstreamMsg = sanitizeUpstreamErrorMessage(upstreamMsg)
+				logBody := s.settingService != nil && s.settingService.cfg != nil && s.settingService.cfg.Gateway.LogUpstreamErrorBody
+				maxBytes := 2048
+				if s.settingService != nil && s.settingService.cfg != nil && s.settingService.cfg.Gateway.LogUpstreamErrorBodyMaxBytes > 0 {
+					maxBytes = s.settingService.cfg.Gateway.LogUpstreamErrorBodyMaxBytes
+				}
+				upstreamDetail := ""
+				if logBody {
+					upstreamDetail = truncateString(string(respBody), maxBytes)
+				}
+				appendOpsUpstreamError(c, OpsUpstreamErrorEvent{
+					Platform:           account.Platform,
+					AccountID:          account.ID,
+					AccountName:        account.Name,
+					UpstreamStatusCode: resp.StatusCode,
+					UpstreamRequestID:  resp.Header.Get("x-request-id"),
+					Kind:               "prompt_too_long",
+					Message:            upstreamMsg,
+					Detail:             upstreamDetail,
+				})
+				return nil, &PromptTooLongError{
+					StatusCode: resp.StatusCode,
+					RequestID:  resp.Header.Get("x-request-id"),
+					Body:       respBody,
+				}
+			}
 			s.handleUpstreamError(ctx, prefix, account, resp.StatusCode, resp.Header, respBody, quotaScope)
 
 			if s.shouldFailoverUpstreamError(resp.StatusCode) {
@@ -1019,21 +1063,55 @@ func isSignatureRelatedError(respBody []byte) bool {
 	return false
 }
 
+func isPromptTooLongError(respBody []byte) bool {
+	msg := strings.ToLower(strings.TrimSpace(extractAntigravityErrorMessage(respBody)))
+	if msg == "" {
+		msg = strings.ToLower(string(respBody))
+	}
+	return strings.Contains(msg, "prompt is too long")
+}
+
 func extractAntigravityErrorMessage(body []byte) string {
 	var payload map[string]any
 	if err := json.Unmarshal(body, &payload); err != nil {
 		return ""
 	}
 
+	parseNestedMessage := func(msg string) string {
+		trimmed := strings.TrimSpace(msg)
+		if trimmed == "" || !strings.HasPrefix(trimmed, "{") {
+			return ""
+		}
+		var nested map[string]any
+		if err := json.Unmarshal([]byte(trimmed), &nested); err != nil {
+			return ""
+		}
+		if errObj, ok := nested["error"].(map[string]any); ok {
+			if innerMsg, ok := errObj["message"].(string); ok && strings.TrimSpace(innerMsg) != "" {
+				return innerMsg
+			}
+		}
+		if innerMsg, ok := nested["message"].(string); ok && strings.TrimSpace(innerMsg) != "" {
+			return innerMsg
+		}
+		return ""
+	}
+
 	// Google-style: {"error": {"message": "..."}}
 	if errObj, ok := payload["error"].(map[string]any); ok {
 		if msg, ok := errObj["message"].(string); ok && strings.TrimSpace(msg) != "" {
+			if innerMsg := parseNestedMessage(msg); innerMsg != "" {
+				return innerMsg
+			}
 			return msg
 		}
 	}
 
 	// Fallback: top-level message
 	if msg, ok := payload["message"].(string); ok && strings.TrimSpace(msg) != "" {
+		if innerMsg := parseNestedMessage(msg); innerMsg != "" {
+			return innerMsg
+		}
 		return msg
 	}
 
@@ -2209,6 +2287,10 @@ func (s *AntigravityGatewayService) writeMappedClaudeError(c *gin.Context, accou
 	return fmt.Errorf("upstream error: %d message=%s", upstreamStatus, upstreamMsg)
 }
 
+func (s *AntigravityGatewayService) WriteMappedClaudeError(c *gin.Context, account *Account, upstreamStatus int, upstreamRequestID string, body []byte) error {
+	return s.writeMappedClaudeError(c, account, upstreamStatus, upstreamRequestID, body)
+}
+
 func (s *AntigravityGatewayService) writeGoogleError(c *gin.Context, status int, message string) error {
 	statusStr := "UNKNOWN"
 	switch status {

backend/internal/service/antigravity_gateway_service_test.go

@@ -1,10 +1,16 @@
 package service
 
 import (
+	"bytes"
+	"context"
 	"encoding/json"
+	"io"
+	"net/http"
+	"net/http/httptest"
 	"testing"
 
 	"github.com/Wei-Shaw/sub2api/internal/pkg/antigravity"
+	"github.com/gin-gonic/gin"
 	"github.com/stretchr/testify/require"
 )
 
@@ -81,3 +87,77 @@ func TestStripThinkingFromClaudeRequest_DoesNotDowngradeTools(t *testing.T) {
 	require.Equal(t, "secret plan", blocks[0]["text"])
 	require.Equal(t, "tool_use", blocks[1]["type"])
 }
+
+func TestIsPromptTooLongError(t *testing.T) {
+	require.True(t, isPromptTooLongError([]byte(`{"error":{"message":"Prompt is too long"}}`)))
+	require.True(t, isPromptTooLongError([]byte(`{"message":"Prompt is too long"}`)))
+	require.False(t, isPromptTooLongError([]byte(`{"error":{"message":"other"}}`)))
+}
+
+type httpUpstreamStub struct {
+	resp *http.Response
+	err  error
+}
+
+func (s *httpUpstreamStub) Do(_ *http.Request, _ string, _ int64, _ int) (*http.Response, error) {
+	return s.resp, s.err
+}
+
+func TestAntigravityGatewayService_Forward_PromptTooLong(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	writer := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(writer)
+
+	body, err := json.Marshal(map[string]any{
+		"model": "claude-opus-4-5",
+		"messages": []map[string]any{
+			{"role": "user", "content": "hi"},
+		},
+		"max_tokens": 1,
+		"stream":     false,
+	})
+	require.NoError(t, err)
+
+	req := httptest.NewRequest(http.MethodPost, "/v1/messages", bytes.NewReader(body))
+	c.Request = req
+
+	respBody := []byte(`{"error":{"message":"Prompt is too long"}}`)
+	resp := &http.Response{
+		StatusCode: http.StatusBadRequest,
+		Header:     http.Header{"X-Request-Id": []string{"req-1"}},
+		Body:       io.NopCloser(bytes.NewReader(respBody)),
+	}
+
+	svc := &AntigravityGatewayService{
+		tokenProvider: &AntigravityTokenProvider{},
+		httpUpstream:  &httpUpstreamStub{resp: resp},
+	}
+
+	account := &Account{
+		ID:          1,
+		Name:        "acc-1",
+		Platform:    PlatformAntigravity,
+		Type:        AccountTypeOAuth,
+		Status:      StatusActive,
+		Concurrency: 1,
+		Credentials: map[string]any{
+			"access_token": "token",
+		},
+	}
+
+	result, err := svc.Forward(context.Background(), c, account, body)
+	require.Nil(t, result)
+
+	var promptErr *PromptTooLongError
+	require.ErrorAs(t, err, &promptErr)
+	require.Equal(t, http.StatusBadRequest, promptErr.StatusCode)
+	require.Equal(t, "req-1", promptErr.RequestID)
+	require.NotEmpty(t, promptErr.Body)
+
+	raw, ok := c.Get(OpsUpstreamErrorsKey)
+	require.True(t, ok)
+	events, ok := raw.([]*OpsUpstreamErrorEvent)
+	require.True(t, ok)
+	require.Len(t, events, 1)
+	require.Equal(t, "prompt_too_long", events[0].Kind)
+}

backend/internal/service/api_key_auth_cache.go

@@ -23,20 +23,21 @@ type APIKeyAuthUserSnapshot struct {
 
 // APIKeyAuthGroupSnapshot 分组快照
 type APIKeyAuthGroupSnapshot struct {
-	ID               int64    `json:"id"`
+	ID                              int64    `json:"id"`
-	Name             string   `json:"name"`
+	Name                            string   `json:"name"`
-	Platform         string   `json:"platform"`
+	Platform                        string   `json:"platform"`
-	Status           string   `json:"status"`
+	Status                          string   `json:"status"`
-	SubscriptionType string   `json:"subscription_type"`
+	SubscriptionType                string   `json:"subscription_type"`
-	RateMultiplier   float64  `json:"rate_multiplier"`
+	RateMultiplier                  float64  `json:"rate_multiplier"`
-	DailyLimitUSD    *float64 `json:"daily_limit_usd,omitempty"`
+	DailyLimitUSD                   *float64 `json:"daily_limit_usd,omitempty"`
-	WeeklyLimitUSD   *float64 `json:"weekly_limit_usd,omitempty"`
+	WeeklyLimitUSD                  *float64 `json:"weekly_limit_usd,omitempty"`
-	MonthlyLimitUSD  *float64 `json:"monthly_limit_usd,omitempty"`
+	MonthlyLimitUSD                 *float64 `json:"monthly_limit_usd,omitempty"`
-	ImagePrice1K     *float64 `json:"image_price_1k,omitempty"`
+	ImagePrice1K                    *float64 `json:"image_price_1k,omitempty"`
-	ImagePrice2K     *float64 `json:"image_price_2k,omitempty"`
+	ImagePrice2K                    *float64 `json:"image_price_2k,omitempty"`
-	ImagePrice4K     *float64 `json:"image_price_4k,omitempty"`
+	ImagePrice4K                    *float64 `json:"image_price_4k,omitempty"`
-	ClaudeCodeOnly   bool     `json:"claude_code_only"`
+	ClaudeCodeOnly                  bool     `json:"claude_code_only"`
-	FallbackGroupID  *int64   `json:"fallback_group_id,omitempty"`
+	FallbackGroupID                 *int64   `json:"fallback_group_id,omitempty"`
+	FallbackGroupIDOnInvalidRequest *int64   `json:"fallback_group_id_on_invalid_request,omitempty"`
 
 	// Model routing is used by gateway account selection, so it must be part of auth cache snapshot.
 	// Only anthropic groups use these fields; others may leave them empty.

backend/internal/service/api_key_auth_cache_impl.go

@@ -207,22 +207,23 @@ func (s *APIKeyService) snapshotFromAPIKey(apiKey *APIKey) *APIKeyAuthSnapshot {
 	}
 	if apiKey.Group != nil {
 		snapshot.Group = &APIKeyAuthGroupSnapshot{
-			ID:                  apiKey.Group.ID,
+			ID:                              apiKey.Group.ID,
-			Name:                apiKey.Group.Name,
+			Name:                            apiKey.Group.Name,
-			Platform:            apiKey.Group.Platform,
+			Platform:                        apiKey.Group.Platform,
-			Status:              apiKey.Group.Status,
+			Status:                          apiKey.Group.Status,
-			SubscriptionType:    apiKey.Group.SubscriptionType,
+			SubscriptionType:                apiKey.Group.SubscriptionType,
-			RateMultiplier:      apiKey.Group.RateMultiplier,
+			RateMultiplier:                  apiKey.Group.RateMultiplier,
-			DailyLimitUSD:       apiKey.Group.DailyLimitUSD,
+			DailyLimitUSD:                   apiKey.Group.DailyLimitUSD,
-			WeeklyLimitUSD:      apiKey.Group.WeeklyLimitUSD,
+			WeeklyLimitUSD:                  apiKey.Group.WeeklyLimitUSD,
-			MonthlyLimitUSD:     apiKey.Group.MonthlyLimitUSD,
+			MonthlyLimitUSD:                 apiKey.Group.MonthlyLimitUSD,
-			ImagePrice1K:        apiKey.Group.ImagePrice1K,
+			ImagePrice1K:                    apiKey.Group.ImagePrice1K,
-			ImagePrice2K:        apiKey.Group.ImagePrice2K,
+			ImagePrice2K:                    apiKey.Group.ImagePrice2K,
-			ImagePrice4K:        apiKey.Group.ImagePrice4K,
+			ImagePrice4K:                    apiKey.Group.ImagePrice4K,
-			ClaudeCodeOnly:      apiKey.Group.ClaudeCodeOnly,
+			ClaudeCodeOnly:                  apiKey.Group.ClaudeCodeOnly,
-			FallbackGroupID:     apiKey.Group.FallbackGroupID,
+			FallbackGroupID:                 apiKey.Group.FallbackGroupID,
-			ModelRouting:        apiKey.Group.ModelRouting,
+			FallbackGroupIDOnInvalidRequest: apiKey.Group.FallbackGroupIDOnInvalidRequest,
-			ModelRoutingEnabled: apiKey.Group.ModelRoutingEnabled,
+			ModelRouting:                    apiKey.Group.ModelRouting,
+			ModelRoutingEnabled:             apiKey.Group.ModelRoutingEnabled,
 		}
 	}
 	return snapshot
@@ -250,23 +251,24 @@ func (s *APIKeyService) snapshotToAPIKey(key string, snapshot *APIKeyAuthSnapsho
 	}
 	if snapshot.Group != nil {
 		apiKey.Group = &Group{
-			ID:                  snapshot.Group.ID,
+			ID:                              snapshot.Group.ID,
-			Name:                snapshot.Group.Name,
+			Name:                            snapshot.Group.Name,
-			Platform:            snapshot.Group.Platform,
+			Platform:                        snapshot.Group.Platform,
-			Status:              snapshot.Group.Status,
+			Status:                          snapshot.Group.Status,
-			Hydrated:            true,
+			Hydrated:                        true,
-			SubscriptionType:    snapshot.Group.SubscriptionType,
+			SubscriptionType:                snapshot.Group.SubscriptionType,
-			RateMultiplier:      snapshot.Group.RateMultiplier,
+			RateMultiplier:                  snapshot.Group.RateMultiplier,
-			DailyLimitUSD:       snapshot.Group.DailyLimitUSD,
+			DailyLimitUSD:                   snapshot.Group.DailyLimitUSD,
-			WeeklyLimitUSD:      snapshot.Group.WeeklyLimitUSD,
+			WeeklyLimitUSD:                  snapshot.Group.WeeklyLimitUSD,
-			MonthlyLimitUSD:     snapshot.Group.MonthlyLimitUSD,
+			MonthlyLimitUSD:                 snapshot.Group.MonthlyLimitUSD,
-			ImagePrice1K:        snapshot.Group.ImagePrice1K,
+			ImagePrice1K:                    snapshot.Group.ImagePrice1K,
-			ImagePrice2K:        snapshot.Group.ImagePrice2K,
+			ImagePrice2K:                    snapshot.Group.ImagePrice2K,
-			ImagePrice4K:        snapshot.Group.ImagePrice4K,
+			ImagePrice4K:                    snapshot.Group.ImagePrice4K,
-			ClaudeCodeOnly:      snapshot.Group.ClaudeCodeOnly,
+			ClaudeCodeOnly:                  snapshot.Group.ClaudeCodeOnly,
-			FallbackGroupID:     snapshot.Group.FallbackGroupID,
+			FallbackGroupID:                 snapshot.Group.FallbackGroupID,
-			ModelRouting:        snapshot.Group.ModelRouting,
+			FallbackGroupIDOnInvalidRequest: snapshot.Group.FallbackGroupIDOnInvalidRequest,
-			ModelRoutingEnabled: snapshot.Group.ModelRoutingEnabled,
+			ModelRouting:                    snapshot.Group.ModelRouting,
+			ModelRoutingEnabled:             snapshot.Group.ModelRoutingEnabled,
 		}
 	}
 	return apiKey

backend/internal/service/gateway_service.go

@@ -55,6 +55,15 @@ func shortSessionHash(sessionHash string) string {
 	return sessionHash[:8]
 }
 
+func normalizeClaudeModelForAnthropic(requestedModel string) string {
+	for _, prefix := range anthropicPrefixMappings {
+		if strings.HasPrefix(requestedModel, prefix) {
+			return prefix
+		}
+	}
+	return requestedModel
+}
+
 // sseDataRe matches SSE data lines with optional whitespace after colon.
 // Some upstream APIs return non-standard "data:" without space (should be "data: ").
 var (
@@ -71,6 +80,12 @@ var (
 		"You are a file search specialist for Claude Code",                     // Explore Agent 版
 		"You are a helpful AI assistant tasked with summarizing conversations", // Compact 版
 	}
+
+	anthropicPrefixMappings = []string{
+		"claude-opus-4-5",
+		"claude-haiku-4-5",
+		"claude-sonnet-4-5",
+	}
 )
 
 // ErrClaudeCodeOnly 表示分组仅允许 Claude Code 客户端访问
@@ -951,6 +966,10 @@ func (s *GatewayService) resolveGroupByID(ctx context.Context, groupID int64) (*
 	return group, nil
 }
 
+func (s *GatewayService) ResolveGroupByID(ctx context.Context, groupID int64) (*Group, error) {
+	return s.resolveGroupByID(ctx, groupID)
+}
+
 func (s *GatewayService) routingAccountIDsForRequest(ctx context.Context, groupID *int64, requestedModel string, platform string) []int64 {
 	if groupID == nil || requestedModel == "" || platform != PlatformAnthropic {
 		return nil
@@ -1016,7 +1035,7 @@ func (s *GatewayService) checkClaudeCodeRestriction(ctx context.Context, groupID
 	}
 
 	// 强制平台模式不检查 Claude Code 限制
-	if _, hasForcePlatform := ctx.Value(ctxkey.ForcePlatform).(string); hasForcePlatform {
+	if forcePlatform, hasForcePlatform := ctx.Value(ctxkey.ForcePlatform).(string); hasForcePlatform && forcePlatform != "" {
 		return nil, groupID, nil
 	}
 
@@ -1719,6 +1738,9 @@ func (s *GatewayService) isModelSupportedByAccount(account *Account, requestedMo
 		// Antigravity 平台使用专门的模型支持检查
 		return IsAntigravityModelSupported(requestedModel)
 	}
+	if account.Platform == PlatformAnthropic {
+		requestedModel = normalizeClaudeModelForAnthropic(requestedModel)
+	}
 	// 其他平台使用账户的模型支持检查
 	return account.IsModelSupported(requestedModel)
 }
@@ -2115,17 +2137,29 @@ func (s *GatewayService) Forward(ctx context.Context, c *gin.Context, account *A
 	// 强制执行 cache_control 块数量限制（最多 4 个）
 	body = enforceCacheControlLimit(body)
 
-	// 应用模型映射（仅对apikey类型账号）
+	// 应用模型映射（APIKey 明确映射优先，其次使用 Anthropic 前缀映射）
 	originalModel := reqModel
+	mappedModel := reqModel
+	mappingSource := ""
 	if account.Type == AccountTypeAPIKey {
-		mappedModel := account.GetMappedModel(reqModel)
+		mappedModel = account.GetMappedModel(reqModel)
 		if mappedModel != reqModel {
-			// 替换请求体中的模型名
+			mappingSource = "account"
-			body = s.replaceModelInBody(body, mappedModel)
-			reqModel = mappedModel
-			log.Printf("Model mapping applied: %s -> %s (account: %s)", originalModel, mappedModel, account.Name)
 		}
 	}
+	if mappingSource == "" && account.Platform == PlatformAnthropic {
+		normalized := normalizeClaudeModelForAnthropic(reqModel)
+		if normalized != reqModel {
+			mappedModel = normalized
+			mappingSource = "prefix"
+		}
+	}
+	if mappedModel != reqModel {
+		// 替换请求体中的模型名
+		body = s.replaceModelInBody(body, mappedModel)
+		reqModel = mappedModel
+		log.Printf("Model mapping applied: %s -> %s (account: %s, source=%s)", originalModel, mappedModel, account.Name, mappingSource)
+	}
 
 	// 获取凭证
 	token, tokenType, err := s.GetAccessToken(ctx, account)
@@ -3426,16 +3460,28 @@ func (s *GatewayService) ForwardCountTokens(ctx context.Context, c *gin.Context,
 		return nil
 	}
 
-	// 应用模型映射（仅对 apikey 类型账号）
+	// 应用模型映射（APIKey 明确映射优先，其次使用 Anthropic 前缀映射）
-	if account.Type == AccountTypeAPIKey {
+	if reqModel != "" {
-		if reqModel != "" {
+		mappedModel := reqModel
-			mappedModel := account.GetMappedModel(reqModel)
+		mappingSource := ""
+		if account.Type == AccountTypeAPIKey {
+			mappedModel = account.GetMappedModel(reqModel)
 			if mappedModel != reqModel {
-				body = s.replaceModelInBody(body, mappedModel)
+				mappingSource = "account"
-				reqModel = mappedModel
-				log.Printf("CountTokens model mapping applied: %s -> %s (account: %s)", parsed.Model, mappedModel, account.Name)
 			}
 		}
+		if mappingSource == "" && account.Platform == PlatformAnthropic {
+			normalized := normalizeClaudeModelForAnthropic(reqModel)
+			if normalized != reqModel {
+				mappedModel = normalized
+				mappingSource = "prefix"
+			}
+		}
+		if mappedModel != reqModel {
+			body = s.replaceModelInBody(body, mappedModel)
+			reqModel = mappedModel
+			log.Printf("CountTokens model mapping applied: %s -> %s (account: %s, source=%s)", parsed.Model, mappedModel, account.Name, mappingSource)
+		}
 	}
 
 	// 获取凭证

backend/internal/service/group.go

@@ -29,6 +29,8 @@ type Group struct {
 	// Claude Code 客户端限制
 	ClaudeCodeOnly  bool
 	FallbackGroupID *int64
+	// 无效请求兜底分组（仅 anthropic 平台使用）
+	FallbackGroupIDOnInvalidRequest *int64
 
 	// 模型路由配置
 	// key: 模型匹配模式（支持 * 通配符，如 "claude-opus-*"）

backend/migrations/043_add_group_invalid_request_fallback.sql

@@ -0,0 +1,13 @@
+-- 043_add_group_invalid_request_fallback.sql
+-- 添加无效请求兜底分组配置
+
+-- 添加 fallback_group_id_on_invalid_request 字段：无效请求兜底使用的分组
+ALTER TABLE groups
+ADD COLUMN IF NOT EXISTS fallback_group_id_on_invalid_request BIGINT REFERENCES groups(id) ON DELETE SET NULL;
+
+-- 添加索引优化查询
+CREATE INDEX IF NOT EXISTS idx_groups_fallback_group_id_on_invalid_request
+ON groups(fallback_group_id_on_invalid_request) WHERE deleted_at IS NULL AND fallback_group_id_on_invalid_request IS NOT NULL;
+
+-- 添加字段注释
+COMMENT ON COLUMN groups.fallback_group_id_on_invalid_request IS '无效请求兜底使用的分组 ID';

frontend/src/i18n/locales/en.ts

@@ -919,6 +919,11 @@ export default {
         fallbackHint: 'Non-Claude Code requests will use this group. Leave empty to reject directly.',
         noFallback: 'No Fallback (Reject)'
       },
+      invalidRequestFallback: {
+        title: 'Invalid Request Fallback Group',
+        hint: 'Triggered only when upstream explicitly returns prompt too long. Leave empty to disable fallback.',
+        noFallback: 'No Fallback'
+      },
       modelRouting: {
         title: 'Model Routing',
         tooltip: 'Configure specific model requests to be routed to designated accounts. Supports wildcard matching, e.g., claude-opus-* matches all opus models.',

frontend/src/i18n/locales/zh.ts

@@ -995,6 +995,11 @@ export default {
         fallbackHint: '非 Claude Code 请求将使用此分组，留空则直接拒绝',
         noFallback: '不降级（直接拒绝）'
       },
+      invalidRequestFallback: {
+        title: '无效请求兜底分组',
+        hint: '仅当上游明确返回 prompt too long 时才会触发，留空表示不兜底',
+        noFallback: '不兜底'
+      },
       modelRouting: {
         title: '模型路由配置',
         tooltip: '配置特定模型请求优先路由到指定账号。支持通配符匹配，如 claude-opus-* 匹配所有 opus 模型。',

frontend/src/types/index.ts

@@ -269,6 +269,7 @@ export interface Group {
   // Claude Code 客户端限制
   claude_code_only: boolean
   fallback_group_id: number | null
+  fallback_group_id_on_invalid_request: number | null
   // 模型路由配置（仅 anthropic 平台使用）
   model_routing: Record<string, number[]> | null
   model_routing_enabled: boolean
@@ -322,6 +323,7 @@ export interface CreateGroupRequest {
   image_price_4k?: number | null
   claude_code_only?: boolean
   fallback_group_id?: number | null
+  fallback_group_id_on_invalid_request?: number | null
 }
 
 export interface UpdateGroupRequest {
@@ -340,6 +342,7 @@ export interface UpdateGroupRequest {
   image_price_4k?: number | null
   claude_code_only?: boolean
   fallback_group_id?: number | null
+  fallback_group_id_on_invalid_request?: number | null
 }
 
 // ==================== Account & Proxy Types ====================

frontend/src/views/admin/GroupsView.vue

@@ -460,6 +460,20 @@
           </div>
         </div>
 
+        <!-- 无效请求兜底（仅 anthropic/antigravity 平台，且非订阅分组） -->
+        <div
+          v-if="['anthropic', 'antigravity'].includes(createForm.platform) && createForm.subscription_type !== 'subscription'"
+          class="border-t pt-4"
+        >
+          <label class="input-label">{{ t('admin.groups.invalidRequestFallback.title') }}</label>
+          <Select
+            v-model="createForm.fallback_group_id_on_invalid_request"
+            :options="invalidRequestFallbackOptions"
+            :placeholder="t('admin.groups.invalidRequestFallback.noFallback')"
+          />
+          <p class="input-hint">{{ t('admin.groups.invalidRequestFallback.hint') }}</p>
+        </div>
+
         <!-- 模型路由配置（仅 anthropic 平台） -->
         <div v-if="createForm.platform === 'anthropic'" class="border-t pt-4">
           <div class="mb-1.5 flex items-center gap-1">
@@ -904,6 +918,20 @@
           </div>
         </div>
 
+        <!-- 无效请求兜底（仅 anthropic/antigravity 平台，且非订阅分组） -->
+        <div
+          v-if="['anthropic', 'antigravity'].includes(editForm.platform) && editForm.subscription_type !== 'subscription'"
+          class="border-t pt-4"
+        >
+          <label class="input-label">{{ t('admin.groups.invalidRequestFallback.title') }}</label>
+          <Select
+            v-model="editForm.fallback_group_id_on_invalid_request"
+            :options="invalidRequestFallbackOptionsForEdit"
+            :placeholder="t('admin.groups.invalidRequestFallback.noFallback')"
+          />
+          <p class="input-hint">{{ t('admin.groups.invalidRequestFallback.hint') }}</p>
+        </div>
+
         <!-- 模型路由配置（仅 anthropic 平台） -->
         <div v-if="editForm.platform === 'anthropic'" class="border-t pt-4">
           <div class="mb-1.5 flex items-center gap-1">
@@ -1202,6 +1230,44 @@ const fallbackGroupOptionsForEdit = computed(() => {
   return options
 })
 
+// 无效请求兜底分组选项（创建时）- 仅包含 anthropic 平台、非订阅且未配置兜底的分组
+const invalidRequestFallbackOptions = computed(() => {
+  const options: { value: number | null; label: string }[] = [
+    { value: null, label: t('admin.groups.invalidRequestFallback.noFallback') }
+  ]
+  const eligibleGroups = groups.value.filter(
+    (g) =>
+      g.platform === 'anthropic' &&
+      g.status === 'active' &&
+      g.subscription_type !== 'subscription' &&
+      g.fallback_group_id_on_invalid_request === null
+  )
+  eligibleGroups.forEach((g) => {
+    options.push({ value: g.id, label: g.name })
+  })
+  return options
+})
+
+// 无效请求兜底分组选项（编辑时）- 排除自身
+const invalidRequestFallbackOptionsForEdit = computed(() => {
+  const options: { value: number | null; label: string }[] = [
+    { value: null, label: t('admin.groups.invalidRequestFallback.noFallback') }
+  ]
+  const currentId = editingGroup.value?.id
+  const eligibleGroups = groups.value.filter(
+    (g) =>
+      g.platform === 'anthropic' &&
+      g.status === 'active' &&
+      g.subscription_type !== 'subscription' &&
+      g.fallback_group_id_on_invalid_request === null &&
+      g.id !== currentId
+  )
+  eligibleGroups.forEach((g) => {
+    options.push({ value: g.id, label: g.name })
+  })
+  return options
+})
+
 const groups = ref<Group[]>([])
 const loading = ref(false)
 const searchQuery = ref('')
@@ -1243,6 +1309,7 @@ const createForm = reactive({
   // Claude Code 客户端限制（仅 anthropic 平台使用）
   claude_code_only: false,
   fallback_group_id: null as number | null,
+  fallback_group_id_on_invalid_request: null as number | null,
   // 模型路由开关
   model_routing_enabled: false
 })
@@ -1414,6 +1481,7 @@ const editForm = reactive({
   // Claude Code 客户端限制（仅 anthropic 平台使用）
   claude_code_only: false,
   fallback_group_id: null as number | null,
+  fallback_group_id_on_invalid_request: null as number | null,
   // 模型路由开关
   model_routing_enabled: false
 })
@@ -1497,6 +1565,7 @@ const closeCreateModal = () => {
   createForm.image_price_4k = null
   createForm.claude_code_only = false
   createForm.fallback_group_id = null
+  createForm.fallback_group_id_on_invalid_request = null
   createModelRoutingRules.value = []
 }
 
@@ -1546,6 +1615,7 @@ const handleEdit = async (group: Group) => {
   editForm.image_price_4k = group.image_price_4k
   editForm.claude_code_only = group.claude_code_only || false
   editForm.fallback_group_id = group.fallback_group_id
+  editForm.fallback_group_id_on_invalid_request = group.fallback_group_id_on_invalid_request
   editForm.model_routing_enabled = group.model_routing_enabled || false
   // 加载模型路由规则（异步加载账号名称）
   editModelRoutingRules.value = await convertApiFormatToRoutingRules(group.model_routing)
@@ -1571,6 +1641,10 @@ const handleUpdateGroup = async () => {
     const payload = {
       ...editForm,
       fallback_group_id: editForm.fallback_group_id === null ? 0 : editForm.fallback_group_id,
+      fallback_group_id_on_invalid_request:
+        editForm.fallback_group_id_on_invalid_request === null
+          ? 0
+          : editForm.fallback_group_id_on_invalid_request,
       model_routing: convertRoutingRulesToApiFormat(editModelRoutingRules.value)
     }
     await adminAPI.groups.update(editingGroup.value.id, payload)
@@ -1612,6 +1686,16 @@ watch(
     if (newVal === 'subscription') {
       createForm.rate_multiplier = 1.0
       createForm.is_exclusive = true
+      createForm.fallback_group_id_on_invalid_request = null
+    }
+  }
+)
+
+watch(
+  () => createForm.platform,
+  (newVal) => {
+    if (!['anthropic', 'antigravity'].includes(newVal)) {
+      createForm.fallback_group_id_on_invalid_request = null
     }
   }
 )