diff --git a/backend/internal/service/openai_compact_sse_keepalive.go b/backend/internal/service/openai_compact_sse_keepalive.go
index 70ef3fc01ad..4d4543f477c 100644
--- a/backend/internal/service/openai_compact_sse_keepalive.go
+++ b/backend/internal/service/openai_compact_sse_keepalive.go
@@ -1,6 +1,9 @@
 package service
 
 import (
+	"bufio"
+	"errors"
+	"net"
 	"net/http"
 	"sync"
 	"time"
@@ -181,52 +184,105 @@ type openAICompactKeepaliveWriter struct {
 // suspend 停拍心跳；幂等。任何响应构造（含 Header 访问——写响应必先操作
 // 响应头）都视为请求侧接管 ResponseWriter。
 func (w *openAICompactKeepaliveWriter) suspend() {
+	if w.k == nil {
+		return
+	}
 	w.k.Stop()
 }
 
 func (w *openAICompactKeepaliveWriter) Header() http.Header {
 	w.suspend()
+	if w.ResponseWriter == nil {
+		return http.Header{}
+	}
 	return w.ResponseWriter.Header()
 }
 
 func (w *openAICompactKeepaliveWriter) Write(data []byte) (int, error) {
 	w.suspend()
+	if w.ResponseWriter == nil {
+		return 0, nil
+	}
 	return w.ResponseWriter.Write(data)
 }
 
 func (w *openAICompactKeepaliveWriter) WriteString(s string) (int, error) {
 	w.suspend()
+	if w.ResponseWriter == nil {
+		return 0, nil
+	}
 	return w.ResponseWriter.WriteString(s)
 }
 
 func (w *openAICompactKeepaliveWriter) WriteHeader(code int) {
 	w.suspend()
+	if w.ResponseWriter == nil {
+		return
+	}
 	w.ResponseWriter.WriteHeader(code)
 }
 
 func (w *openAICompactKeepaliveWriter) WriteHeaderNow() {
 	w.suspend()
+	if w.ResponseWriter == nil {
+		return
+	}
 	w.ResponseWriter.WriteHeaderNow()
 }
 
 func (w *openAICompactKeepaliveWriter) Flush() {
 	w.suspend()
+	if w.ResponseWriter == nil {
+		return
+	}
 	w.ResponseWriter.Flush()
 }
 
+func (w *openAICompactKeepaliveWriter) Hijack() (net.Conn, *bufio.ReadWriter, error) {
+	if w.ResponseWriter == nil {
+		return nil, nil, errors.New("response writer released")
+	}
+	return w.ResponseWriter.Hijack()
+}
+
+func (w *openAICompactKeepaliveWriter) CloseNotify() <-chan bool {
+	if w.ResponseWriter == nil {
+		ch := make(chan bool)
+		close(ch)
+		return ch
+	}
+	return w.ResponseWriter.CloseNotify()
+}
+
+func (w *openAICompactKeepaliveWriter) Pusher() http.Pusher {
+	if w.ResponseWriter == nil {
+		return nil
+	}
+	return w.ResponseWriter.Pusher()
+}
+
 func (w *openAICompactKeepaliveWriter) Status() int {
+	if w.k == nil || w.ResponseWriter == nil {
+		return 0
+	}
 	w.k.mu.Lock()
 	defer w.k.mu.Unlock()
 	return w.ResponseWriter.Status()
 }
 
 func (w *openAICompactKeepaliveWriter) Size() int {
+	if w.k == nil || w.ResponseWriter == nil {
+		return 0
+	}
 	w.k.mu.Lock()
 	defer w.k.mu.Unlock()
 	return w.ResponseWriter.Size()
 }
 
 func (w *openAICompactKeepaliveWriter) Written() bool {
+	if w.k == nil || w.ResponseWriter == nil {
+		return false
+	}
 	w.k.mu.Lock()
 	defer w.k.mu.Unlock()
 	return w.ResponseWriter.Written()
diff --git a/backend/internal/service/openai_compact_sse_keepalive_test.go b/backend/internal/service/openai_compact_sse_keepalive_test.go
index 3b217a07184..1efed7e9e47 100644
--- a/backend/internal/service/openai_compact_sse_keepalive_test.go
+++ b/backend/internal/service/openai_compact_sse_keepalive_test.go
@@ -6,6 +6,7 @@ import (
 	"testing"
 	"time"
 
+	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 	"github.com/tidwall/gjson"
 )
@@ -141,6 +142,110 @@ func TestOpenAICompactKeepaliveWriter_RequestSideWriteSuspendsBeats(t *testing.T
 	require.Contains(t, rec.Body.String(), `{"error":"local reject"}`)
 }
 
+func TestOpenAICompactKeepaliveWriter_NilInnerWriter_NoPanic(t *testing.T) {
+	w := &openAICompactKeepaliveWriter{
+		k: &openAICompactSSEKeepalive{stop: make(chan struct{})},
+	}
+	w.ResponseWriter = nil
+
+	assert.NotPanics(t, func() {
+		assert.Equal(t, 0, w.Status())
+	})
+	assert.NotPanics(t, func() {
+		assert.Equal(t, 0, w.Size())
+	})
+	assert.NotPanics(t, func() {
+		assert.False(t, w.Written())
+	})
+	assert.NotPanics(t, func() {
+		assert.NotNil(t, w.Header())
+	})
+	assert.NotPanics(t, func() {
+		n, err := w.Write([]byte("test"))
+		assert.Equal(t, 0, n)
+		assert.NoError(t, err)
+	})
+	assert.NotPanics(t, func() {
+		n, err := w.WriteString("test")
+		assert.Equal(t, 0, n)
+		assert.NoError(t, err)
+	})
+	assert.NotPanics(t, func() {
+		w.WriteHeader(http.StatusOK)
+	})
+	assert.NotPanics(t, func() {
+		w.WriteHeaderNow()
+	})
+	assert.NotPanics(t, func() {
+		w.Flush()
+	})
+	assert.NotPanics(t, func() {
+		conn, rw, err := w.Hijack()
+		assert.Nil(t, conn)
+		assert.Nil(t, rw)
+		assert.Error(t, err)
+	})
+	assert.NotPanics(t, func() {
+		ch := w.CloseNotify()
+		assert.NotNil(t, ch)
+	})
+	assert.NotPanics(t, func() {
+		assert.Nil(t, w.Pusher())
+	})
+}
+
+func TestOpenAICompactKeepaliveWriter_NilKeepalive_NoPanic(t *testing.T) {
+	c, rec := newCompactBridgeTestContext(t, true)
+	w := &openAICompactKeepaliveWriter{ResponseWriter: c.Writer}
+
+	assert.NotPanics(t, func() {
+		assert.Equal(t, 0, w.Status())
+	})
+	assert.NotPanics(t, func() {
+		assert.Equal(t, 0, w.Size())
+	})
+	assert.NotPanics(t, func() {
+		assert.False(t, w.Written())
+	})
+	assert.NotPanics(t, func() {
+		w.Header().Set("X-Test", "ok")
+	})
+	assert.NotPanics(t, func() {
+		w.WriteHeader(http.StatusAccepted)
+	})
+	assert.NotPanics(t, func() {
+		n, err := w.WriteString("ok")
+		assert.Equal(t, 2, n)
+		assert.NoError(t, err)
+	})
+	assert.NotPanics(t, func() {
+		w.Flush()
+	})
+	require.Equal(t, "ok", rec.Header().Get("X-Test"))
+	require.Equal(t, "ok", rec.Body.String())
+}
+
+func TestOpenAICompactKeepaliveWriter_DelegatesWhenReady(t *testing.T) {
+	c, rec := newCompactBridgeTestContext(t, true)
+	stop := StartOpenAICompactSSEKeepalive(c, time.Hour)
+	defer stop()
+
+	w, ok := c.Writer.(*openAICompactKeepaliveWriter)
+	require.True(t, ok)
+
+	w.Header().Set("X-Test", "ok")
+	w.WriteHeader(http.StatusAccepted)
+	n, err := w.WriteString("ready")
+	require.NoError(t, err)
+	require.Equal(t, len("ready"), n)
+
+	require.Equal(t, http.StatusAccepted, w.Status())
+	require.Equal(t, len("ready"), w.Size())
+	require.True(t, w.Written())
+	require.Equal(t, "ok", rec.Header().Get("X-Test"))
+	require.Equal(t, "ready", rec.Body.String())
+}
+
 // fast policy block 在心跳提交后必须降级为 response.failed 终止事件。
 func TestWriteOpenAIFastPolicyBlockedResponse_AfterKeepaliveCommit(t *testing.T) {
 	c, rec := newCompactBridgeTestContext(t, true)