fix(stream): 修复流式请求超时和取消归因问题

- 流式请求 timeout 改为 None，避免 provider.request_timeout 作为整条流总时长超时导致长响应被硬切断
- 重构 CancelledError 断连归因逻辑：提取探测方法并支持多次重试确认，降低误判率
- 新增 cancelled_unknown 状态处理断连检测不确定的场景，避免错误归因为 server_cancelled
- 在 upstream_response 中记录取消详情，便于排查
- 新增断连归因逻辑的单元测试

src/api/handlers/base/chat_handler_base.py

@@ -1143,11 +1143,11 @@ class ChatHandlerBase(BaseMessageHandler, ABC):
                 url=url,
                 headers=provider_headers,
                 payload=provider_payload,
-                timeout=(
-                    provider.request_timeout or config.http_request_timeout
-                    if delegate_cfg
-                    else None
-                ),
+                # 流式请求不应使用 provider.request_timeout 作为“整条流总时长”超时，
+                # 否则会在长响应中途被硬切断（常见于 request_timeout=15s 的配置）。
+                # 首字节超时由外层 wait_for(stream_first_byte_timeout) 控制；
+                # 后续分块读取由 http client 默认 read timeout（长超时）控制。
+                timeout=None,
             )
             response_ctx = http_client.stream(**_skw)
             stream_response = await response_ctx.__aenter__()

src/api/handlers/base/cli_monitor_mixin.py

@@ -32,6 +32,67 @@ if TYPE_CHECKING:
 class CliMonitorMixin:
     """监控和统计相关方法的 Mixin"""
 
+    # CancelledError 归因时，断连检查参数（秒）
+    CANCEL_DISCONNECT_CHECK_TIMEOUT_SECONDS = 0.5
+    CANCEL_DISCONNECT_RETRY_DELAYS_SECONDS = (0.1, 0.2)
+
+    async def _probe_client_disconnect(
+        self,
+        http_request: Request,
+        *,
+        request_id: str,
+    ) -> tuple[bool, bool]:
+        """单次探测客户端是否断连。
+
+        Returns:
+            (is_disconnected, is_indeterminate)
+        """
+        try:
+            disconnected = await asyncio.wait_for(
+                asyncio.shield(http_request.is_disconnected()),
+                timeout=self.CANCEL_DISCONNECT_CHECK_TIMEOUT_SECONDS,
+            )
+            return bool(disconnected), False
+        except (asyncio.CancelledError, asyncio.TimeoutError):
+            return False, True
+        except Exception as e:
+            logger.debug("ID:{} | cancel 断连检测失败: {}", request_id, e)
+            return False, True
+
+    async def _confirm_client_disconnect(
+        self,
+        http_request: Request,
+        *,
+        request_id: str,
+    ) -> tuple[bool, bool]:
+        """CancelledError 场景下做多次断连确认，降低误判。
+
+        Returns:
+            (is_client_disconnected, check_indeterminate)
+        """
+        disconnected, uncertain = await self._probe_client_disconnect(
+            http_request,
+            request_id=request_id,
+        )
+        if disconnected:
+            return True, uncertain
+
+        for delay in self.CANCEL_DISCONNECT_RETRY_DELAYS_SECONDS:
+            try:
+                await asyncio.sleep(delay)
+            except asyncio.CancelledError:
+                # 重试期间协程再次被取消，无法继续探测，标记为不确定
+                return False, True
+            disconnected, step_uncertain = await self._probe_client_disconnect(
+                http_request,
+                request_id=request_id,
+            )
+            uncertain = uncertain or step_uncertain
+            if disconnected:
+                return True, uncertain
+
+        return False, uncertain
+
     async def _create_monitored_stream(
         self,
         ctx: StreamContext,
@@ -111,26 +172,21 @@ class CliMonitorMixin:
             time_since_last_chunk = time_module.time() - last_chunk_time
 
             is_client_disconnected = False
+            disconnect_check_uncertain = False
             if http_request is not None:
-                try:
-                    # shield + timeout: 避免在取消态下二次被 CancelledError 打断，尽力取到断连状态
-                    # 限时 0.5s 防止极端情况下的阻塞
-                    is_client_disconnected = await asyncio.wait_for(
-                        asyncio.shield(http_request.is_disconnected()),
-                        timeout=0.5,
+                is_client_disconnected, disconnect_check_uncertain = (
+                    await self._confirm_client_disconnect(
+                        http_request,
+                        request_id=ctx.request_id,
                     )
-                except (asyncio.CancelledError, asyncio.TimeoutError):
-                    # 无法在取消态/超时下完成断连检查，保守视为未知（不强行归因为客户端）
-                    is_client_disconnected = False
-                except Exception as e:
-                    logger.debug("ID:{} | cancel 断连检测失败: {}", ctx.request_id, e)
-                    is_client_disconnected = False
+                )
 
             # 如果响应已完成，不标记为失败/取消
             if not ctx.has_completion:
                 if is_client_disconnected:
                     ctx.status_code = 499
                     ctx.error_message = "client_disconnected"
+                    cancel_origin = "client_disconnected"
                     logger.warning(
                         f"ID:{ctx.request_id} | Stream cancelled by client: "
                         f"chunks={chunk_count}, "
@@ -138,10 +194,23 @@ class CliMonitorMixin:
                         f"time_since_last_chunk={time_since_last_chunk:.2f}s, "
                         f"output_tokens={ctx.output_tokens}"
                     )
+                elif disconnect_check_uncertain:
+                    # 断连检查本身不稳定（超时/取消/异常）时，避免直接定性为 server_cancelled。
+                    ctx.status_code = 503
+                    ctx.error_message = "cancelled_unknown"
+                    cancel_origin = "cancelled_unknown"
+                    logger.warning(
+                        f"ID:{ctx.request_id} | Stream cancelled with unknown origin: "
+                        f"chunks={chunk_count}, "
+                        f"has_completion={ctx.has_completion}, "
+                        f"time_since_last_chunk={time_since_last_chunk:.2f}s, "
+                        f"output_tokens={ctx.output_tokens}"
+                    )
                 else:
                     # 服务端中断（例如重载/关停/内部取消） -- 不应伪装成客户端取消
                     ctx.status_code = 503
                     ctx.error_message = "server_cancelled"
+                    cancel_origin = "server_cancelled"
                     logger.error(
                         f"ID:{ctx.request_id} | Stream interrupted by server: "
                         f"chunks={chunk_count}, "
@@ -149,6 +218,13 @@ class CliMonitorMixin:
                         f"time_since_last_chunk={time_since_last_chunk:.2f}s, "
                         f"output_tokens={ctx.output_tokens}"
                     )
+                ctx.upstream_response = (
+                    f"cancel_origin={cancel_origin}, "
+                    f"chunks={chunk_count}, "
+                    f"has_completion={ctx.has_completion}, "
+                    f"time_since_last_chunk={time_since_last_chunk:.2f}s, "
+                    f"output_tokens={ctx.output_tokens}"
+                )
             raise
         except httpx.TimeoutException as e:
             ctx.status_code = 504

src/api/handlers/base/cli_stream_mixin.py

@@ -658,11 +658,11 @@ class CliStreamMixin:
                 url=url,
                 headers=provider_headers,
                 payload=provider_payload,
-                timeout=(
-                    provider.request_timeout or config.http_request_timeout
-                    if delegate_cfg
-                    else None
-                ),
+                # 流式请求不应使用 provider.request_timeout 作为“整条流总时长”超时，
+                # 否则会在长响应中途被硬切断（常见于 request_timeout=15s 的配置）。
+                # 首字节超时由外层 wait_for(stream_first_byte_timeout) 控制；
+                # 后续分块读取由 http client 默认 read timeout（长超时）控制。
+                timeout=None,
             )
             _connect_start = time.monotonic()
             response_ctx = http_client.stream(**_skw)