修复代理与日志链路的可靠性问题

tests/proxy/robustness_test.go

@@ -108,6 +108,38 @@ func TestRequestBodyReadFailureReturnsFixed400WithoutUpstream(t *testing.T) {
 	}
 }
 
+func TestRequestBodyOverLimitReturns413WithoutUpstream(t *testing.T) {
+	var upstreamCalls atomic.Int32
+	upstream := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		upstreamCalls.Add(1)
+		w.WriteHeader(http.StatusOK)
+	}))
+	defer upstream.Close()
+	u, _ := url.Parse(upstream.URL)
+	h := newTestHandler(t, u, &captureSubmitter{}, proxy.Options{MaxRequestBytes: 4})
+
+	for _, tc := range []struct {
+		name          string
+		contentLength int64
+	}{
+		{name: "known length", contentLength: 5},
+		{name: "chunked", contentLength: -1},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			req := httptest.NewRequest(http.MethodPost, "http://proxy.test/v1/chat", strings.NewReader("12345"))
+			req.ContentLength = tc.contentLength
+			rec := httptest.NewRecorder()
+			h.ServeHTTP(rec, req)
+			if rec.Code != http.StatusRequestEntityTooLarge || rec.Body.String() != "request body too large\n" {
+				t.Fatalf("response=(%d, %q), want fixed 413", rec.Code, rec.Body.String())
+			}
+		})
+	}
+	if upstreamCalls.Load() != 0 {
+		t.Fatalf("upstream called %d times", upstreamCalls.Load())
+	}
+}
+
 func TestRequestBodyReadFailureWithZeroContentLengthDoesNotReachUpstream(t *testing.T) {
 	var upstreamCalls atomic.Int32
 	upstream := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {