fix(openai): do not normalize API token based accounts

backend/internal/service/openai_codex_transform.go

@@ -275,6 +275,13 @@ func normalizeCodexModel(model string) string {
 	return "gpt-5.1"
 }
 
+func normalizeOpenAIModelForUpstream(account *Account, model string) string {
+	if account == nil || account.Type == AccountTypeOAuth {
+		return normalizeCodexModel(model)
+	}
+	return strings.TrimSpace(model)
+}
+
 func SupportsVerbosity(model string) bool {
 	if !strings.HasPrefix(model, "gpt-") {
 		return true

backend/internal/service/openai_gateway_service.go

@@ -1938,9 +1938,11 @@ func (s *OpenAIGatewayService) Forward(ctx context.Context, c *gin.Context, acco
 	}
 	upstreamModel := billingModel
 
-	// 针对所有 OpenAI 账号执行 Codex 模型名规范化，确保上游识别一致。
+	// OpenAI OAuth 账号走 ChatGPT internal Codex endpoint，需要将模型名规范化为
+	// 上游可识别的 Codex/GPT 系列。API Key 账号则应保留原始/映射后的模型名，
+	// 以兼容自定义 base_url 的 OpenAI-compatible 上游。
 	if model, ok := reqBody["model"].(string); ok {
-		upstreamModel = normalizeCodexModel(model)
+		upstreamModel = normalizeOpenAIModelForUpstream(account, model)
 		if upstreamModel != "" && upstreamModel != model {
 			logger.LegacyPrintf("service.openai_gateway", "[OpenAI] Upstream model resolved: %s -> %s (account: %s, type: %s, isCodexCLI: %v)",
 				model, upstreamModel, account.Name, account.Type, isCodexCLI)

backend/internal/service/openai_model_mapping_test.go

@@ -99,3 +99,39 @@ func TestNormalizeCodexModel(t *testing.T) {
 		}
 	}
 }
+
+func TestNormalizeOpenAIModelForUpstream(t *testing.T) {
+	tests := []struct {
+		name    string
+		account *Account
+		model   string
+		want    string
+	}{
+		{
+			name:    "oauth keeps codex normalization behavior",
+			account: &Account{Type: AccountTypeOAuth},
+			model:   "gemini-3-flash-preview",
+			want:    "gpt-5.1",
+		},
+		{
+			name:    "apikey preserves custom compatible model",
+			account: &Account{Type: AccountTypeAPIKey},
+			model:   "gemini-3-flash-preview",
+			want:    "gemini-3-flash-preview",
+		},
+		{
+			name:    "apikey preserves official non codex model",
+			account: &Account{Type: AccountTypeAPIKey},
+			model:   "gpt-4.1",
+			want:    "gpt-4.1",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := normalizeOpenAIModelForUpstream(tt.account, tt.model); got != tt.want {
+				t.Fatalf("normalizeOpenAIModelForUpstream(...) = %q, want %q", got, tt.want)
+			}
+		})
+	}
+}