diff --git a/api/middleware/log.go b/api/middleware/log.go
index 1a5ef7400..c9cb0720a 100644
--- a/api/middleware/log.go
+++ b/api/middleware/log.go
@@ -8,14 +8,10 @@ import (
 
 	"github.com/gin-gonic/gin"
 	"opencsg.com/csghub-server/api/httpbase"
+	commonutils "opencsg.com/csghub-server/common/utils/common"
 	"opencsg.com/csghub-server/common/utils/trace"
 )
 
-// Status 499 is a non-standard code introduced by nginx to indicate
-// "Client Closed Request" — the client disconnected before the server
-// finished processing.
-const StatusClientClosedRequest = 499
-
 func Log() gin.HandlerFunc {
 	return func(ctx *gin.Context) {
 		if ctx.Request.URL.Path == "/healthz" {
@@ -43,7 +39,7 @@ func Log() gin.HandlerFunc {
 			// If the client disconnected (timeout or explicit cancel),
 			// override the logged status to 499.
 			if ctx.Request.Context().Err() == context.Canceled {
-				status = StatusClientClosedRequest
+				status = commonutils.StatusClientClosedRequest
 			}
 
 			// Derive a non-canceled context for the log call.
diff --git a/api/middleware/log_test.go b/api/middleware/log_test.go
index 29951ce64..9ff41c789 100644
--- a/api/middleware/log_test.go
+++ b/api/middleware/log_test.go
@@ -13,6 +13,7 @@ import (
 	"github.com/gin-gonic/gin"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
+	commonutils "opencsg.com/csghub-server/common/utils/common"
 )
 
 // captureLog is a helper that installs a slog JSON handler writing to a buffer
@@ -82,7 +83,7 @@ func TestLog_ClientCancelBeforeHandler(t *testing.T) {
 
 	logs := readLogs()
 	require.Len(t, logs, 1, "must emit a log even when client canceled")
-	assert.Equal(t, float64(StatusClientClosedRequest), logs[0]["status"], "status should be 499 for client cancel")
+	assert.Equal(t, float64(commonutils.StatusClientClosedRequest), logs[0]["status"], "status should be 499 for client cancel")
 	assert.Equal(t, "/test", logs[0]["url"])
 }
 
@@ -116,7 +117,7 @@ func TestLog_ClientCancelDuringSlowHandler(t *testing.T) {
 
 	logs := readLogs()
 	require.Len(t, logs, 1, "must emit a log when client cancels during slow handler")
-	assert.Equal(t, float64(StatusClientClosedRequest), logs[0]["status"], "status should be 499")
+	assert.Equal(t, float64(commonutils.StatusClientClosedRequest), logs[0]["status"], "status should be 499")
 }
 
 func TestLog_HandlerPanicWithRecovery(t *testing.T) {
diff --git a/builder/proxy/reverse_proxy.go b/builder/proxy/reverse_proxy.go
index ad4e37e4f..6c3fbb19d 100644
--- a/builder/proxy/reverse_proxy.go
+++ b/builder/proxy/reverse_proxy.go
@@ -1,12 +1,15 @@
 package proxy
 
 import (
+	"context"
+	"errors"
 	"log/slog"
 	"net/http"
 	"net/http/httputil"
 	"net/url"
 
 	"github.com/openai/openai-go/v3"
+	commonutils "opencsg.com/csghub-server/common/utils/common"
 	"opencsg.com/csghub-server/common/utils/trace"
 )
 
@@ -54,6 +57,15 @@ func (rp *reverseProxyImpl) ServeHTTP(w http.ResponseWriter, r *http.Request, ap
 		}
 	}()
 	proxy := httputil.NewSingleHostReverseProxy(rp.target)
+	proxy.ErrorHandler = func(rw http.ResponseWriter, req *http.Request, err error) {
+		if errors.Is(err, context.Canceled) {
+			slog.InfoContext(context.WithoutCancel(req.Context()), "http: proxy request canceled", slog.Any("error", err))
+			rw.WriteHeader(commonutils.StatusClientClosedRequest)
+			return
+		}
+		slog.ErrorContext(req.Context(), "http: proxy error", slog.Any("error", err))
+		rw.WriteHeader(http.StatusBadGateway)
+	}
 	proxy.Director = func(req *http.Request) {
 		if len(svcHost) > 0 {
 			slog.Info("update reverse proxy header host", slog.Any("svc-host", svcHost))
diff --git a/builder/proxy/reverse_proxy_test.go b/builder/proxy/reverse_proxy_test.go
index d3a37b33a..407088d18 100644
--- a/builder/proxy/reverse_proxy_test.go
+++ b/builder/proxy/reverse_proxy_test.go
@@ -1,11 +1,13 @@
 package proxy
 
 import (
+	"context"
 	"net/http"
 	"net/http/httptest"
 	"testing"
 
 	"github.com/stretchr/testify/require"
+	commonutils "opencsg.com/csghub-server/common/utils/common"
 )
 
 func TestReverseProxy_AcceptEncodingDefaultGzip(t *testing.T) {
@@ -47,6 +49,24 @@ func TestReverseProxy_AcceptEncodingDisabled(t *testing.T) {
 	require.Equal(t, "identity", downstreamAcceptEncoding)
 }
 
+func TestReverseProxy_ContextCanceledWritesClientClosed(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusOK)
+	}))
+	defer server.Close()
+
+	rp, err := NewReverseProxy(server.URL)
+	require.NoError(t, err)
+
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel()
+	req := httptest.NewRequest(http.MethodGet, "/", nil).WithContext(ctx)
+	resp := httptest.NewRecorder()
+	rp.ServeHTTP(resp, req, "", "")
+
+	require.Equal(t, commonutils.StatusClientClosedRequest, resp.Code)
+}
+
 // import (
 // 	"bytes"
 // 	"io"
diff --git a/common/utils/common/http_status.go b/common/utils/common/http_status.go
new file mode 100644
index 000000000..0dca01d33
--- /dev/null
+++ b/common/utils/common/http_status.go
@@ -0,0 +1,5 @@
+package common
+
+// StatusClientClosedRequest is the non-standard nginx status code for a client
+// closing the request before the server finishes processing it.
+const StatusClientClosedRequest = 499