diff --git a/backend/internal/service/gateway_anthropic_apikey_passthrough_test.go b/backend/internal/service/gateway_anthropic_apikey_passthrough_test.go
index 7bd4cd8a..e3dff6b8 100644
--- a/backend/internal/service/gateway_anthropic_apikey_passthrough_test.go
+++ b/backend/internal/service/gateway_anthropic_apikey_passthrough_test.go
@@ -4,6 +4,7 @@ import (
 	"bufio"
 	"bytes"
 	"context"
+	"encoding/json"
 	"errors"
 	"io"
 	"net/http"
@@ -346,9 +347,15 @@ func TestGatewayService_AnthropicAPIKeyPassthrough_CountTokens404PassthroughNotE
 			err := svc.ForwardCountTokens(context.Background(), c, account, parsed)
 
 			if tt.wantPassthrough {
-				// 404 透传：返回 nil（不记录为错误），但 HTTP 状态码是 404
+				// 返回 nil（不记录为错误），HTTP 状态码 404 + Anthropic 错误体
 				require.NoError(t, err)
 				require.Equal(t, http.StatusNotFound, rec.Code)
+				var errResp map[string]any
+				require.NoError(t, json.Unmarshal(rec.Body.Bytes(), &errResp))
+				require.Equal(t, "error", errResp["type"])
+				errObj, ok := errResp["error"].(map[string]any)
+				require.True(t, ok)
+				require.Equal(t, "not_found_error", errObj["type"])
 			} else {
 				require.Error(t, err)
 				require.Equal(t, tt.statusCode, rec.Code)
diff --git a/backend/internal/service/gateway_service.go b/backend/internal/service/gateway_service.go
index 8f33678b..02a4b012 100644
--- a/backend/internal/service/gateway_service.go
+++ b/backend/internal/service/gateway_service.go
@@ -6223,11 +6223,11 @@ func (s *GatewayService) forwardCountTokensAnthropicAPIKeyPassthrough(ctx contex
 		upstreamMsg := strings.TrimSpace(extractUpstreamErrorMessage(respBody))
 		upstreamMsg = sanitizeUpstreamErrorMessage(upstreamMsg)
 
-		// 中转站不支持 count_tokens 端点时（404），透传 404 让客户端 fallback 到本地估算。
+		// 中转站不支持 count_tokens 端点时（404），返回 404 让客户端 fallback 到本地估算。
 		// 返回 nil 避免 handler 层记录为错误，也不设置 ops 上游错误上下文。
 		if resp.StatusCode == http.StatusNotFound {
 			logger.LegacyPrintf("service.gateway",
-				"[count_tokens] Upstream does not support count_tokens (404), passing through: account=%d name=%s msg=%s",
+				"[count_tokens] Upstream does not support count_tokens (404), returning 404: account=%d name=%s msg=%s",
 				account.ID, account.Name, truncateString(upstreamMsg, 512))
 			s.countTokensError(c, http.StatusNotFound, "not_found_error", "count_tokens endpoint is not supported by upstream")
 			return nil