diff --git a/backend/internal/handler/gateway_handler.go b/backend/internal/handler/gateway_handler.go
index b95e67c3..7e6b2f03 100644
--- a/backend/internal/handler/gateway_handler.go
+++ b/backend/internal/handler/gateway_handler.go
@@ -137,6 +137,11 @@ func (h *GatewayHandler) Messages(c *gin.Context) {
 	// Track if we've started streaming (for error handling)
 	streamStarted := false
 
+	// 绑定错误透传服务，允许 service 层在非 failover 错误场景复用规则。
+	if h.errorPassthroughService != nil {
+		service.BindErrorPassthroughService(c, h.errorPassthroughService)
+	}
+
 	// 获取订阅信息（可能为nil）- 提前获取用于后续检查
 	subscription, _ := middleware2.GetSubscriptionFromContext(c)
 
diff --git a/backend/internal/handler/gemini_v1beta_handler.go b/backend/internal/handler/gemini_v1beta_handler.go
index a43c5eb9..cc71e8e6 100644
--- a/backend/internal/handler/gemini_v1beta_handler.go
+++ b/backend/internal/handler/gemini_v1beta_handler.go
@@ -209,6 +209,9 @@ func (h *GatewayHandler) GeminiV1BetaModels(c *gin.Context) {
 
 	// 1) user concurrency slot
 	streamStarted := false
+	if h.errorPassthroughService != nil {
+		service.BindErrorPassthroughService(c, h.errorPassthroughService)
+	}
 	userReleaseFunc, err := geminiConcurrency.AcquireUserSlotWithWait(c, authSubject.UserID, authSubject.Concurrency, stream, &streamStarted)
 	if err != nil {
 		googleError(c, http.StatusTooManyRequests, err.Error())
diff --git a/backend/internal/handler/openai_gateway_handler.go b/backend/internal/handler/openai_gateway_handler.go
index 1dcb163b..835297b8 100644
--- a/backend/internal/handler/openai_gateway_handler.go
+++ b/backend/internal/handler/openai_gateway_handler.go
@@ -149,6 +149,11 @@ func (h *OpenAIGatewayHandler) Responses(c *gin.Context) {
 	// Track if we've started streaming (for error handling)
 	streamStarted := false
 
+	// 绑定错误透传服务，允许 service 层在非 failover 错误场景复用规则。
+	if h.errorPassthroughService != nil {
+		service.BindErrorPassthroughService(c, h.errorPassthroughService)
+	}
+
 	// Get subscription info (may be nil)
 	subscription, _ := middleware2.GetSubscriptionFromContext(c)
 
diff --git a/backend/internal/service/error_passthrough_runtime.go b/backend/internal/service/error_passthrough_runtime.go
new file mode 100644
index 00000000..65085d6f
--- /dev/null
+++ b/backend/internal/service/error_passthrough_runtime.go
@@ -0,0 +1,67 @@
+package service
+
+import "github.com/gin-gonic/gin"
+
+const errorPassthroughServiceContextKey = "error_passthrough_service"
+
+// BindErrorPassthroughService 将错误透传服务绑定到请求上下文，供 service 层在非 failover 场景下复用规则。
+func BindErrorPassthroughService(c *gin.Context, svc *ErrorPassthroughService) {
+	if c == nil || svc == nil {
+		return
+	}
+	c.Set(errorPassthroughServiceContextKey, svc)
+}
+
+func getBoundErrorPassthroughService(c *gin.Context) *ErrorPassthroughService {
+	if c == nil {
+		return nil
+	}
+	v, ok := c.Get(errorPassthroughServiceContextKey)
+	if !ok {
+		return nil
+	}
+	svc, ok := v.(*ErrorPassthroughService)
+	if !ok {
+		return nil
+	}
+	return svc
+}
+
+// applyErrorPassthroughRule 按规则改写错误响应；未命中时返回默认响应参数。
+func applyErrorPassthroughRule(
+	c *gin.Context,
+	platform string,
+	upstreamStatus int,
+	responseBody []byte,
+	defaultStatus int,
+	defaultErrType string,
+	defaultErrMsg string,
+) (status int, errType string, errMsg string, matched bool) {
+	status = defaultStatus
+	errType = defaultErrType
+	errMsg = defaultErrMsg
+
+	svc := getBoundErrorPassthroughService(c)
+	if svc == nil {
+		return status, errType, errMsg, false
+	}
+
+	rule := svc.MatchRule(platform, upstreamStatus, responseBody)
+	if rule == nil {
+		return status, errType, errMsg, false
+	}
+
+	status = upstreamStatus
+	if !rule.PassthroughCode && rule.ResponseCode != nil {
+		status = *rule.ResponseCode
+	}
+
+	errMsg = ExtractUpstreamErrorMessage(responseBody)
+	if !rule.PassthroughBody && rule.CustomMessage != nil {
+		errMsg = *rule.CustomMessage
+	}
+
+	// 与现有 failover 场景保持一致：命中规则时统一返回 upstream_error。
+	errType = "upstream_error"
+	return status, errType, errMsg, true
+}
diff --git a/backend/internal/service/error_passthrough_runtime_test.go b/backend/internal/service/error_passthrough_runtime_test.go
new file mode 100644
index 00000000..393e6e59
--- /dev/null
+++ b/backend/internal/service/error_passthrough_runtime_test.go
@@ -0,0 +1,211 @@
+package service
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/Wei-Shaw/sub2api/internal/model"
+	"github.com/gin-gonic/gin"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestApplyErrorPassthroughRule_NoBoundService(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	rec := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(rec)
+
+	status, errType, errMsg, matched := applyErrorPassthroughRule(
+		c,
+		PlatformAnthropic,
+		http.StatusUnprocessableEntity,
+		[]byte(`{"error":{"message":"invalid schema"}}`),
+		http.StatusBadGateway,
+		"upstream_error",
+		"Upstream request failed",
+	)
+
+	assert.False(t, matched)
+	assert.Equal(t, http.StatusBadGateway, status)
+	assert.Equal(t, "upstream_error", errType)
+	assert.Equal(t, "Upstream request failed", errMsg)
+}
+
+func TestGatewayHandleErrorResponse_NoRuleKeepsDefault(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	rec := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(rec)
+
+	svc := &GatewayService{}
+	respBody := []byte(`{"error":{"message":"Invalid schema for field messages"}}`)
+	resp := &http.Response{
+		StatusCode: http.StatusUnprocessableEntity,
+		Body:       io.NopCloser(bytes.NewReader(respBody)),
+		Header:     http.Header{},
+	}
+	account := &Account{ID: 11, Platform: PlatformAnthropic, Type: AccountTypeAPIKey}
+
+	_, err := svc.handleErrorResponse(context.Background(), resp, c, account)
+	require.Error(t, err)
+	assert.Equal(t, http.StatusBadGateway, rec.Code)
+
+	var payload map[string]any
+	require.NoError(t, json.Unmarshal(rec.Body.Bytes(), &payload))
+	errField, ok := payload["error"].(map[string]any)
+	require.True(t, ok)
+	assert.Equal(t, "upstream_error", errField["type"])
+	assert.Equal(t, "Upstream request failed", errField["message"])
+}
+
+func TestOpenAIHandleErrorResponse_NoRuleKeepsDefault(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	rec := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(rec)
+
+	svc := &OpenAIGatewayService{}
+	respBody := []byte(`{"error":{"message":"Invalid schema for field messages"}}`)
+	resp := &http.Response{
+		StatusCode: http.StatusUnprocessableEntity,
+		Body:       io.NopCloser(bytes.NewReader(respBody)),
+		Header:     http.Header{},
+	}
+	account := &Account{ID: 12, Platform: PlatformOpenAI, Type: AccountTypeAPIKey}
+
+	_, err := svc.handleErrorResponse(context.Background(), resp, c, account)
+	require.Error(t, err)
+	assert.Equal(t, http.StatusBadGateway, rec.Code)
+
+	var payload map[string]any
+	require.NoError(t, json.Unmarshal(rec.Body.Bytes(), &payload))
+	errField, ok := payload["error"].(map[string]any)
+	require.True(t, ok)
+	assert.Equal(t, "upstream_error", errField["type"])
+	assert.Equal(t, "Upstream request failed", errField["message"])
+}
+
+func TestGeminiWriteGeminiMappedError_NoRuleKeepsDefault(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	rec := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(rec)
+
+	svc := &GeminiMessagesCompatService{}
+	respBody := []byte(`{"error":{"code":422,"message":"Invalid schema for field messages","status":"INVALID_ARGUMENT"}}`)
+	account := &Account{ID: 13, Platform: PlatformGemini, Type: AccountTypeAPIKey}
+
+	err := svc.writeGeminiMappedError(c, account, http.StatusUnprocessableEntity, "req-2", respBody)
+	require.Error(t, err)
+	assert.Equal(t, http.StatusBadRequest, rec.Code)
+
+	var payload map[string]any
+	require.NoError(t, json.Unmarshal(rec.Body.Bytes(), &payload))
+	errField, ok := payload["error"].(map[string]any)
+	require.True(t, ok)
+	assert.Equal(t, "invalid_request_error", errField["type"])
+	assert.Equal(t, "Upstream request failed", errField["message"])
+}
+
+func TestGatewayHandleErrorResponse_AppliesRuleFor422(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	rec := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(rec)
+
+	ruleSvc := &ErrorPassthroughService{}
+	ruleSvc.setLocalCache([]*model.ErrorPassthroughRule{newNonFailoverPassthroughRule(http.StatusUnprocessableEntity, "invalid schema", http.StatusTeapot, "上游请求失败")})
+	BindErrorPassthroughService(c, ruleSvc)
+
+	svc := &GatewayService{}
+	respBody := []byte(`{"error":{"message":"Invalid schema for field messages"}}`)
+	resp := &http.Response{
+		StatusCode: http.StatusUnprocessableEntity,
+		Body:       io.NopCloser(bytes.NewReader(respBody)),
+		Header:     http.Header{},
+	}
+	account := &Account{ID: 1, Platform: PlatformAnthropic, Type: AccountTypeAPIKey}
+
+	_, err := svc.handleErrorResponse(context.Background(), resp, c, account)
+	require.Error(t, err)
+	assert.Equal(t, http.StatusTeapot, rec.Code)
+
+	var payload map[string]any
+	require.NoError(t, json.Unmarshal(rec.Body.Bytes(), &payload))
+	errField, ok := payload["error"].(map[string]any)
+	require.True(t, ok)
+	assert.Equal(t, "upstream_error", errField["type"])
+	assert.Equal(t, "上游请求失败", errField["message"])
+}
+
+func TestOpenAIHandleErrorResponse_AppliesRuleFor422(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	rec := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(rec)
+
+	ruleSvc := &ErrorPassthroughService{}
+	ruleSvc.setLocalCache([]*model.ErrorPassthroughRule{newNonFailoverPassthroughRule(http.StatusUnprocessableEntity, "invalid schema", http.StatusTeapot, "OpenAI上游失败")})
+	BindErrorPassthroughService(c, ruleSvc)
+
+	svc := &OpenAIGatewayService{}
+	respBody := []byte(`{"error":{"message":"Invalid schema for field messages"}}`)
+	resp := &http.Response{
+		StatusCode: http.StatusUnprocessableEntity,
+		Body:       io.NopCloser(bytes.NewReader(respBody)),
+		Header:     http.Header{},
+	}
+	account := &Account{ID: 2, Platform: PlatformOpenAI, Type: AccountTypeAPIKey}
+
+	_, err := svc.handleErrorResponse(context.Background(), resp, c, account)
+	require.Error(t, err)
+	assert.Equal(t, http.StatusTeapot, rec.Code)
+
+	var payload map[string]any
+	require.NoError(t, json.Unmarshal(rec.Body.Bytes(), &payload))
+	errField, ok := payload["error"].(map[string]any)
+	require.True(t, ok)
+	assert.Equal(t, "upstream_error", errField["type"])
+	assert.Equal(t, "OpenAI上游失败", errField["message"])
+}
+
+func TestGeminiWriteGeminiMappedError_AppliesRuleFor422(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	rec := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(rec)
+
+	ruleSvc := &ErrorPassthroughService{}
+	ruleSvc.setLocalCache([]*model.ErrorPassthroughRule{newNonFailoverPassthroughRule(http.StatusUnprocessableEntity, "invalid schema", http.StatusTeapot, "Gemini上游失败")})
+	BindErrorPassthroughService(c, ruleSvc)
+
+	svc := &GeminiMessagesCompatService{}
+	respBody := []byte(`{"error":{"code":422,"message":"Invalid schema for field messages","status":"INVALID_ARGUMENT"}}`)
+	account := &Account{ID: 3, Platform: PlatformGemini, Type: AccountTypeAPIKey}
+
+	err := svc.writeGeminiMappedError(c, account, http.StatusUnprocessableEntity, "req-1", respBody)
+	require.Error(t, err)
+	assert.Equal(t, http.StatusTeapot, rec.Code)
+
+	var payload map[string]any
+	require.NoError(t, json.Unmarshal(rec.Body.Bytes(), &payload))
+	errField, ok := payload["error"].(map[string]any)
+	require.True(t, ok)
+	assert.Equal(t, "upstream_error", errField["type"])
+	assert.Equal(t, "Gemini上游失败", errField["message"])
+}
+
+func newNonFailoverPassthroughRule(statusCode int, keyword string, respCode int, customMessage string) *model.ErrorPassthroughRule {
+	return &model.ErrorPassthroughRule{
+		ID:              1,
+		Name:            "non-failover-rule",
+		Enabled:         true,
+		Priority:        1,
+		ErrorCodes:      []int{statusCode},
+		Keywords:        []string{keyword},
+		MatchMode:       model.MatchModeAll,
+		PassthroughCode: false,
+		ResponseCode:    &respCode,
+		PassthroughBody: false,
+		CustomMessage:   &customMessage,
+	}
+}
diff --git a/backend/internal/service/gateway_service.go b/backend/internal/service/gateway_service.go
index 7a029d49..250f7bff 100644
--- a/backend/internal/service/gateway_service.go
+++ b/backend/internal/service/gateway_service.go
@@ -2576,24 +2576,20 @@ func (s *GatewayService) selectAccountWithMixedScheduling(ctx context.Context, g
 // 对于 Antigravity 平台，会先获取映射后的最终模型名（包括 thinking 后缀）再检查支持
 func (s *GatewayService) isModelSupportedByAccountWithContext(ctx context.Context, account *Account, requestedModel string) bool {
 	if account.Platform == PlatformAntigravity {
-		// Antigravity 平台使用专门的模型支持检查
 		if strings.TrimSpace(requestedModel) == "" {
 			return true
 		}
-		if !IsAntigravityModelSupported(requestedModel) {
+		// 使用与转发阶段一致的映射逻辑：自定义映射优先 → 默认映射兜底
+		mapped := mapAntigravityModel(account, requestedModel)
+		if mapped == "" {
 			return false
 		}
-		// 先用默认映射获取基础模型名，再应用 thinking 后缀
-		defaultMapped, exists := domain.DefaultAntigravityModelMapping[requestedModel]
-		if !exists || defaultMapped == "" {
-			return false
-		}
-		finalModel := defaultMapped
+		// 应用 thinking 后缀后检查最终模型是否在账号映射中
 		if enabled, ok := ctx.Value(ctxkey.ThinkingEnabled).(bool); ok {
-			finalModel = applyThinkingModelSuffix(finalModel, enabled)
+			finalModel := applyThinkingModelSuffix(mapped, enabled)
+			return account.IsModelSupported(finalModel)
 		}
-		// 使用最终模型名检查 model_mapping 支持
-		return account.IsModelSupported(finalModel)
+		return true
 	}
 	return s.isModelSupportedByAccount(account, requestedModel)
 }
@@ -2601,15 +2597,10 @@ func (s *GatewayService) isModelSupportedByAccountWithContext(ctx context.Contex
 // isModelSupportedByAccount 根据账户平台检查模型支持（无 context，用于非 Antigravity 平台）
 func (s *GatewayService) isModelSupportedByAccount(account *Account, requestedModel string) bool {
 	if account.Platform == PlatformAntigravity {
-		// Antigravity 应使用 isModelSupportedByAccountWithContext
-		// 这里作为兼容保留，使用原始模型名检查
 		if strings.TrimSpace(requestedModel) == "" {
 			return true
 		}
-		if !IsAntigravityModelSupported(requestedModel) {
-			return false
-		}
-		return account.IsModelSupported(requestedModel)
+		return mapAntigravityModel(account, requestedModel) != ""
 	}
 	// OAuth/SetupToken 账号使用 Anthropic 标准映射（短ID → 长ID）
 	if account.Platform == PlatformAnthropic && account.Type != AccountTypeAPIKey {
@@ -3919,6 +3910,34 @@ func (s *GatewayService) handleErrorResponse(ctx context.Context, resp *http.Res
 		)
 	}
 
+	// 非 failover 错误也支持错误透传规则匹配。
+	if status, errType, errMsg, matched := applyErrorPassthroughRule(
+		c,
+		account.Platform,
+		resp.StatusCode,
+		body,
+		http.StatusBadGateway,
+		"upstream_error",
+		"Upstream request failed",
+	); matched {
+		c.JSON(status, gin.H{
+			"type": "error",
+			"error": gin.H{
+				"type":    errType,
+				"message": errMsg,
+			},
+		})
+
+		summary := upstreamMsg
+		if summary == "" {
+			summary = errMsg
+		}
+		if summary == "" {
+			return nil, fmt.Errorf("upstream error: %d (passthrough rule matched)", resp.StatusCode)
+		}
+		return nil, fmt.Errorf("upstream error: %d (passthrough rule matched) message=%s", resp.StatusCode, summary)
+	}
+
 	// 根据状态码返回适当的自定义错误响应（不透传上游详细信息）
 	var errType, errMsg string
 	var statusCode int
@@ -4050,6 +4069,33 @@ func (s *GatewayService) handleRetryExhaustedError(ctx context.Context, resp *ht
 		)
 	}
 
+	if status, errType, errMsg, matched := applyErrorPassthroughRule(
+		c,
+		account.Platform,
+		resp.StatusCode,
+		respBody,
+		http.StatusBadGateway,
+		"upstream_error",
+		"Upstream request failed after retries",
+	); matched {
+		c.JSON(status, gin.H{
+			"type": "error",
+			"error": gin.H{
+				"type":    errType,
+				"message": errMsg,
+			},
+		})
+
+		summary := upstreamMsg
+		if summary == "" {
+			summary = errMsg
+		}
+		if summary == "" {
+			return nil, fmt.Errorf("upstream error: %d (retries exhausted, passthrough rule matched)", resp.StatusCode)
+		}
+		return nil, fmt.Errorf("upstream error: %d (retries exhausted, passthrough rule matched) message=%s", resp.StatusCode, summary)
+	}
+
 	// 返回统一的重试耗尽错误响应
 	c.JSON(http.StatusBadGateway, gin.H{
 		"type": "error",
diff --git a/backend/internal/service/gemini_messages_compat_service.go b/backend/internal/service/gemini_messages_compat_service.go
index 964250d8..0f156c2e 100644
--- a/backend/internal/service/gemini_messages_compat_service.go
+++ b/backend/internal/service/gemini_messages_compat_service.go
@@ -362,7 +362,10 @@ func (s *GeminiMessagesCompatService) isBetterGeminiAccount(candidate, current *
 // isModelSupportedByAccount 根据账户平台检查模型支持
 func (s *GeminiMessagesCompatService) isModelSupportedByAccount(account *Account, requestedModel string) bool {
 	if account.Platform == PlatformAntigravity {
-		return IsAntigravityModelSupported(requestedModel)
+		if strings.TrimSpace(requestedModel) == "" {
+			return true
+		}
+		return mapAntigravityModel(account, requestedModel) != ""
 	}
 	return account.IsModelSupported(requestedModel)
 }
@@ -1498,6 +1501,28 @@ func (s *GeminiMessagesCompatService) writeGeminiMappedError(c *gin.Context, acc
 		log.Printf("[Gemini] upstream error %d: %s", upstreamStatus, truncateForLog(body, s.cfg.Gateway.LogUpstreamErrorBodyMaxBytes))
 	}
 
+	if status, errType, errMsg, matched := applyErrorPassthroughRule(
+		c,
+		PlatformGemini,
+		upstreamStatus,
+		body,
+		http.StatusBadGateway,
+		"upstream_error",
+		"Upstream request failed",
+	); matched {
+		c.JSON(status, gin.H{
+			"type":  "error",
+			"error": gin.H{"type": errType, "message": errMsg},
+		})
+		if upstreamMsg == "" {
+			upstreamMsg = errMsg
+		}
+		if upstreamMsg == "" {
+			return fmt.Errorf("upstream error: %d (passthrough rule matched)", upstreamStatus)
+		}
+		return fmt.Errorf("upstream error: %d (passthrough rule matched) message=%s", upstreamStatus, upstreamMsg)
+	}
+
 	var statusCode int
 	var errType, errMsg string
 
diff --git a/backend/internal/service/openai_gateway_service.go b/backend/internal/service/openai_gateway_service.go
index ae3106d2..fbe81cb4 100644
--- a/backend/internal/service/openai_gateway_service.go
+++ b/backend/internal/service/openai_gateway_service.go
@@ -1087,6 +1087,30 @@ func (s *OpenAIGatewayService) handleErrorResponse(ctx context.Context, resp *ht
 		)
 	}
 
+	if status, errType, errMsg, matched := applyErrorPassthroughRule(
+		c,
+		PlatformOpenAI,
+		resp.StatusCode,
+		body,
+		http.StatusBadGateway,
+		"upstream_error",
+		"Upstream request failed",
+	); matched {
+		c.JSON(status, gin.H{
+			"error": gin.H{
+				"type":    errType,
+				"message": errMsg,
+			},
+		})
+		if upstreamMsg == "" {
+			upstreamMsg = errMsg
+		}
+		if upstreamMsg == "" {
+			return nil, fmt.Errorf("upstream error: %d (passthrough rule matched)", resp.StatusCode)
+		}
+		return nil, fmt.Errorf("upstream error: %d (passthrough rule matched) message=%s", resp.StatusCode, upstreamMsg)
+	}
+
 	// Check custom error codes
 	if !account.ShouldHandleErrorCode(resp.StatusCode) {
 		appendOpsUpstreamError(c, OpsUpstreamErrorEvent{