diff --git a/backend/internal/service/openai_gateway_passthrough.go b/backend/internal/service/openai_gateway_passthrough.go
index ecca154781..0705d897b1 100644
--- a/backend/internal/service/openai_gateway_passthrough.go
+++ b/backend/internal/service/openai_gateway_passthrough.go
@@ -2186,6 +2186,14 @@ func (s *OpenAIGatewayService) handleStreamingResponsePassthrough(
 			responseFailedPending = false
 			failureDelivered = true
 		}
+		// Terminal 事件（response.completed / [DONE] 等）随空行完整刷出后不再等上游
+		// EOF：上游在 keep-alive/HTTP2 复用连接上可能拖延关闭连接（观测到 8~46s 不等），
+		// 空等期间只能靠 keepalive 维持，白白拉长尾延迟。usage 已在 terminal 事件中解析。
+		// Codex bare error 序列（error 后可能跟 response.failed 或翻盘的 completed）
+		// 必须继续读取，不适用提前结束。
+		if (sawDone || sawTerminalEvent) && line == "" && !(codexFailureTerminal && sawBareError) {
+			break
+		}
 	}
 	ensureResponseFailedTerminal()
 	if err := documentScanner.Err(); err != nil {
diff --git a/backend/internal/service/openai_gateway_response_flush_test.go b/backend/internal/service/openai_gateway_response_flush_test.go
index fe6e3ea6b2..56e071041a 100644
--- a/backend/internal/service/openai_gateway_response_flush_test.go
+++ b/backend/internal/service/openai_gateway_response_flush_test.go
@@ -644,3 +644,47 @@ func waitOpenAIResponseFlushSignal(t *testing.T, signal <-chan struct{}) {
 		t.Fatal("timed out waiting for stream signal")
 	}
 }
+
+// hangingOpenAISSEAfterTerminal 模拟上游在发完 terminal 事件后拖延关闭连接
+// （keep-alive/HTTP2 复用连接上观测到 8~46s 不 EOF）。
+type hangingOpenAISSEAfterTerminal struct {
+	payload   []byte
+	sent      bool
+	release   chan struct{}
+	closeOnce sync.Once
+}
+
+func (r *hangingOpenAISSEAfterTerminal) Read(data []byte) (int, error) {
+	if !r.sent {
+		r.sent = true
+		return copy(data, r.payload), nil
+	}
+	<-r.release
+	return 0, io.EOF
+}
+
+func (r *hangingOpenAISSEAfterTerminal) Close() error {
+	r.closeOnce.Do(func() { close(r.release) })
+	return nil
+}
+
+func TestOpenAIResponseFlush_TerminalEventEndsStreamWithoutEOF(t *testing.T) {
+	body := "data: {\"type\":\"response.completed\",\"response\":{\"status\":\"completed\",\"output\":[],\"usage\":{\"input_tokens\":7,\"output_tokens\":5}}}\n\n"
+	reader := &hangingOpenAISSEAfterTerminal{payload: []byte(body), release: make(chan struct{})}
+	recorder := newOpenAIResponseFlushRecorder()
+	resultCh, errCh := runOpenAIResponseFlushTestAsync(recorder, reader, config.GatewayConfig{StreamKeepaliveInterval: 1, StreamDataIntervalTimeout: 30})
+	t.Cleanup(func() { _ = reader.Close() })
+
+	select {
+	case err := <-errCh:
+		require.NoError(t, err)
+		result := <-resultCh
+		require.NotNil(t, result)
+		require.Equal(t, 7, result.usage.InputTokens)
+		require.Equal(t, 5, result.usage.OutputTokens)
+	case <-time.After(3 * time.Second):
+		t.Fatal("stream did not end after terminal event; still waiting for upstream EOF")
+	}
+	gotBody, _ := recorder.snapshot()
+	require.Equal(t, body, gotBody)
+}
diff --git a/backend/internal/service/openai_gateway_response_handling.go b/backend/internal/service/openai_gateway_response_handling.go
index 104f319dc5..021b060c73 100644
--- a/backend/internal/service/openai_gateway_response_handling.go
+++ b/backend/internal/service/openai_gateway_response_handling.go
@@ -798,6 +798,12 @@ func (s *OpenAIGatewayService) handleStreamingResponseWithReasoning(ctx context.
 			if streamEarlyErr != nil {
 				return resultWithUsage(), streamEarlyErr
 			}
+			// Terminal 事件完整写出后直接结束，不等上游 EOF（见下方异步循环同款说明）。
+			// Codex bare error 序列（error 后可能跟 response.failed 或翻盘的 completed）
+			// 必须继续读取，不适用提前结束。
+			if sawTerminalEvent && !eventInProgress && !(codexFailureTerminal && sawBareError) {
+				return finalizeStream()
+			}
 		}
 		if result, err, done := handleScanErr(documentScanner.Err()); done {
 			return result, err
@@ -877,6 +883,15 @@ func (s *OpenAIGatewayService) handleStreamingResponseWithReasoning(ctx context.
 			if streamEarlyErr != nil {
 				return resultWithUsage(), streamEarlyErr
 			}
+			// Terminal 事件（response.completed 等）已完整写出后不再等上游 EOF：
+			// 上游在 keep-alive/HTTP2 复用连接上可能拖延关闭连接，空等期间只能
+			// 靠 keepalive 维持，白白拉长尾延迟。usage 已在 terminal 事件中解析。
+			// Codex bare error 序列（error 后可能跟 response.failed 或翻盘的 completed）
+			// 必须继续读取，不适用提前结束。
+			if sawTerminalEvent && !eventInProgress && !(codexFailureTerminal && sawBareError) {
+				_ = resp.Body.Close()
+				return finalizeStream()
+			}
 
 		case <-intervalCh:
 			if failureDelivered {