fix: honor account model mapping before group fallback

backend/internal/service/account.go

@@ -521,16 +521,23 @@ func (a *Account) IsModelSupported(requestedModel string) bool {
 // GetMappedModel 获取映射后的模型名（支持通配符，最长优先匹配）
 // 如果未配置 mapping，返回原始模型名
 func (a *Account) GetMappedModel(requestedModel string) string {
+	mappedModel, _ := a.ResolveMappedModel(requestedModel)
+	return mappedModel
+}
+
+// ResolveMappedModel 获取映射后的模型名，并返回是否命中了账号级映射。
+// matched=true 表示命中了精确映射或通配符映射，即使映射结果与原模型名相同。
+func (a *Account) ResolveMappedModel(requestedModel string) (mappedModel string, matched bool) {
 	mapping := a.GetModelMapping()
 	if len(mapping) == 0 {
-		return requestedModel
+		return requestedModel, false
 	}
 	// 精确匹配优先
 	if mappedModel, exists := mapping[requestedModel]; exists {
-		return mappedModel
+		return mappedModel, true
 	}
 	// 通配符匹配（最长优先）
-	return matchWildcardMapping(mapping, requestedModel)
+	return matchWildcardMappingResult(mapping, requestedModel)
 }
 
 func (a *Account) GetBaseURL() string {
@@ -607,6 +614,11 @@ func matchWildcard(pattern, str string) bool {
 // matchWildcardMapping 通配符映射匹配（最长优先）
 // 如果没有匹配，返回原始字符串
 func matchWildcardMapping(mapping map[string]string, requestedModel string) string {
+	mappedModel, _ := matchWildcardMappingResult(mapping, requestedModel)
+	return mappedModel
+}
+
+func matchWildcardMappingResult(mapping map[string]string, requestedModel string) (string, bool) {
 	// 收集所有匹配的 pattern，按长度降序排序（最长优先）
 	type patternMatch struct {
 		pattern string
@@ -621,7 +633,7 @@ func matchWildcardMapping(mapping map[string]string, requestedModel string) stri
 	}
 
 	if len(matches) == 0 {
-		return requestedModel // 无匹配，返回原始模型名
+		return requestedModel, false // 无匹配，返回原始模型名
 	}
 
 	// 按 pattern 长度降序排序
@@ -632,7 +644,7 @@ func matchWildcardMapping(mapping map[string]string, requestedModel string) stri
 		return matches[i].pattern < matches[j].pattern
 	})
 
-	return matches[0].target
+	return matches[0].target, true
 }
 
 func (a *Account) IsCustomErrorCodesEnabled() bool {

backend/internal/service/account_wildcard_test.go

@@ -268,6 +268,69 @@ func TestAccountGetMappedModel(t *testing.T) {
 	}
 }
 
+func TestAccountResolveMappedModel(t *testing.T) {
+	tests := []struct {
+		name           string
+		credentials    map[string]any
+		requestedModel string
+		expectedModel  string
+		expectedMatch  bool
+	}{
+		{
+			name:           "no mapping reports unmatched",
+			credentials:    nil,
+			requestedModel: "gpt-5.4",
+			expectedModel:  "gpt-5.4",
+			expectedMatch:  false,
+		},
+		{
+			name: "exact passthrough mapping still counts as matched",
+			credentials: map[string]any{
+				"model_mapping": map[string]any{
+					"gpt-5.4": "gpt-5.4",
+				},
+			},
+			requestedModel: "gpt-5.4",
+			expectedModel:  "gpt-5.4",
+			expectedMatch:  true,
+		},
+		{
+			name: "wildcard passthrough mapping still counts as matched",
+			credentials: map[string]any{
+				"model_mapping": map[string]any{
+					"gpt-*": "gpt-5.4",
+				},
+			},
+			requestedModel: "gpt-5.4",
+			expectedModel:  "gpt-5.4",
+			expectedMatch:  true,
+		},
+		{
+			name: "missing mapping reports unmatched",
+			credentials: map[string]any{
+				"model_mapping": map[string]any{
+					"gpt-5.2": "gpt-5.2",
+				},
+			},
+			requestedModel: "gpt-5.4",
+			expectedModel:  "gpt-5.4",
+			expectedMatch:  false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			account := &Account{
+				Credentials: tt.credentials,
+			}
+			mappedModel, matched := account.ResolveMappedModel(tt.requestedModel)
+			if mappedModel != tt.expectedModel || matched != tt.expectedMatch {
+				t.Fatalf("ResolveMappedModel(%q) = (%q, %v), want (%q, %v)", tt.requestedModel, mappedModel, matched, tt.expectedModel, tt.expectedMatch)
+			}
+		})
+	}
+}
+
 func TestAccountGetModelMapping_AntigravityEnsuresGeminiDefaultPassthroughs(t *testing.T) {
 	account := &Account{
 		Platform: PlatformAntigravity,

backend/internal/service/openai_gateway_chat_completions.go

@@ -51,10 +51,7 @@ func (s *OpenAIGatewayService) ForwardAsChatCompletions(
 	}
 
 	// 3. Model mapping
-	mappedModel := account.GetMappedModel(originalModel)
-	if mappedModel == originalModel && defaultMappedModel != "" {
-		mappedModel = defaultMappedModel
-	}
+	mappedModel := resolveOpenAIForwardModel(account, originalModel, defaultMappedModel)
 	responsesReq.Model = mappedModel
 
 	logger.L().Debug("openai chat_completions: model mapping applied",

backend/internal/service/openai_gateway_messages.go

@@ -59,11 +59,7 @@ func (s *OpenAIGatewayService) ForwardAsAnthropic(
 	}
 
 	// 3. Model mapping
-	mappedModel := account.GetMappedModel(originalModel)
-	// 分组级降级：账号未映射时使用分组默认映射模型
-	if mappedModel == originalModel && defaultMappedModel != "" {
-		mappedModel = defaultMappedModel
-	}
+	mappedModel := resolveOpenAIForwardModel(account, originalModel, defaultMappedModel)
 	responsesReq.Model = mappedModel
 
 	logger.L().Debug("openai messages: model mapping applied",

backend/internal/service/openai_model_mapping.go

@@ -0,0 +1,19 @@
+package service
+
+// resolveOpenAIForwardModel determines the upstream model for OpenAI-compatible
+// forwarding. Group-level default mapping only applies when the account itself
+// did not match any explicit model_mapping rule.
+func resolveOpenAIForwardModel(account *Account, requestedModel, defaultMappedModel string) string {
+	if account == nil {
+		if defaultMappedModel != "" {
+			return defaultMappedModel
+		}
+		return requestedModel
+	}
+
+	mappedModel, matched := account.ResolveMappedModel(requestedModel)
+	if !matched && defaultMappedModel != "" {
+		return defaultMappedModel
+	}
+	return mappedModel
+}

backend/internal/service/openai_model_mapping_test.go

@@ -0,0 +1,70 @@
+package service
+
+import "testing"
+
+func TestResolveOpenAIForwardModel(t *testing.T) {
+	tests := []struct {
+		name               string
+		account            *Account
+		requestedModel     string
+		defaultMappedModel string
+		expectedModel      string
+	}{
+		{
+			name: "falls back to group default when account has no mapping",
+			account: &Account{
+				Credentials: map[string]any{},
+			},
+			requestedModel:     "gpt-5.4",
+			defaultMappedModel: "gpt-4o-mini",
+			expectedModel:      "gpt-4o-mini",
+		},
+		{
+			name: "preserves exact passthrough mapping instead of group default",
+			account: &Account{
+				Credentials: map[string]any{
+					"model_mapping": map[string]any{
+						"gpt-5.4": "gpt-5.4",
+					},
+				},
+			},
+			requestedModel:     "gpt-5.4",
+			defaultMappedModel: "gpt-4o-mini",
+			expectedModel:      "gpt-5.4",
+		},
+		{
+			name: "preserves wildcard passthrough mapping instead of group default",
+			account: &Account{
+				Credentials: map[string]any{
+					"model_mapping": map[string]any{
+						"gpt-*": "gpt-5.4",
+					},
+				},
+			},
+			requestedModel:     "gpt-5.4",
+			defaultMappedModel: "gpt-4o-mini",
+			expectedModel:      "gpt-5.4",
+		},
+		{
+			name: "uses account remap when explicit target differs",
+			account: &Account{
+				Credentials: map[string]any{
+					"model_mapping": map[string]any{
+						"gpt-5": "gpt-5.4",
+					},
+				},
+			},
+			requestedModel:     "gpt-5",
+			defaultMappedModel: "gpt-4o-mini",
+			expectedModel:      "gpt-5.4",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := resolveOpenAIForwardModel(tt.account, tt.requestedModel, tt.defaultMappedModel); got != tt.expectedModel {
+				t.Fatalf("resolveOpenAIForwardModel(...) = %q, want %q", got, tt.expectedModel)
+			}
+		})
+	}
+}