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https://github.com/jxxghp/MoviePilot.git
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fix tool selection middleware
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jxxghp
196
app/agent/middleware/tool_selection.py
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196
app/agent/middleware/tool_selection.py
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"""MoviePilot 自定义工具筛选中间件。"""
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from __future__ import annotations
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import json
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from typing import Any
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from langchain.agents.middleware import LLMToolSelectorMiddleware
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from langchain_core.language_models.chat_models import BaseChatModel
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from app.log import logger
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class MoviePilotToolSelectorMiddleware(LLMToolSelectorMiddleware):
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"""
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为 DeepSeek 兼容端点提供更稳妥的工具筛选实现。
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LangChain 默认会通过 `with_structured_output()` 走 OpenAI 的
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`response_format=json_schema` 路径，但 DeepSeek 官方 OpenAI 兼容端点公开文档
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仅保证 `json_object` 模式可用。对于 `deepseek-reasoner`，这会在工具筛选阶段
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提前触发 400，导致 Agent 还没真正开始执行工具就失败。
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因此这里仅在识别到 DeepSeek 模型/端点时，退回到显式 JSON 输出模式：
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1. 使用 `response_format={"type": "json_object"}`；
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2. 在提示词中明确约束返回 JSON 结构；
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3. 手动解析 `{"tools": [...]}`，其余模型继续沿用 LangChain 默认实现。
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"""
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@staticmethod
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def _is_deepseek_compatible_model(model: BaseChatModel) -> bool:
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"""
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判断当前模型是否应当走 DeepSeek JSON 兼容分支。
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除了官方 `langchain_deepseek`，用户也可能通过 OpenAI-compatible
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配置把 DeepSeek 端点接到 `ChatOpenAI`。因此这里同时检查模块名、模型名
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和 Base URL，避免只靠单一条件漏判。
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"""
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module_name = type(model).__module__.lower()
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model_name = str(
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getattr(model, "model_name", "") or getattr(model, "model", "")
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).strip().lower()
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base_url = str(
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getattr(model, "openai_api_base", "") or getattr(model, "api_base", "")
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).strip().lower()
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return (
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"deepseek" in module_name
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or model_name.startswith("deepseek-")
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or "api.deepseek.com" in base_url
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)
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@staticmethod
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def _extract_text_content(content: Any) -> str:
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"""
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从模型响应中提取纯文本。
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这里不依赖上层 LLMHelper，避免中间件与 LLM 构造逻辑互相耦合。
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"""
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if content is None:
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return ""
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if isinstance(content, str):
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return content
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if isinstance(content, list):
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text_parts: list[str] = []
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for block in content:
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if isinstance(block, str):
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text_parts.append(block)
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continue
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if isinstance(block, dict):
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if block.get("type") == "text" and isinstance(
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block.get("text"), str
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):
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text_parts.append(block["text"])
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continue
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if not block.get("type") and isinstance(block.get("text"), str):
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text_parts.append(block["text"])
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return "".join(text_parts)
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if isinstance(content, dict):
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if content.get("type") == "text" and isinstance(content.get("text"), str):
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return content["text"]
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if not content.get("type") and isinstance(content.get("text"), str):
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return content["text"]
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return ""
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@staticmethod
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def _parse_json_object(text: str) -> dict[str, Any]:
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"""
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解析模型返回的 JSON。
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DeepSeek 在 JSON 模式下通常会返回纯 JSON，但这里仍做一层兜底，
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兼容模型偶发输出围栏或前后说明文本的情况。
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"""
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stripped_text = text.strip()
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if not stripped_text:
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raise ValueError("工具筛选返回了空响应")
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try:
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payload = json.loads(stripped_text)
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if isinstance(payload, dict):
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return payload
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except json.JSONDecodeError:
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pass
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start = stripped_text.find("{")
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end = stripped_text.rfind("}")
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if start == -1 or end == -1 or end <= start:
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raise ValueError(f"工具筛选返回的内容不是合法 JSON: {stripped_text}")
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payload = json.loads(stripped_text[start: end + 1])
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if not isinstance(payload, dict):
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raise ValueError("工具筛选 JSON 顶层必须是对象")
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return payload
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@staticmethod
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def _render_tool_list(available_tools: list[Any]) -> str:
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"""把工具名和描述渲染成稳定的文本列表。"""
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return "\n".join(
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f"- {tool.name}: {tool.description}" for tool in available_tools
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)
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def _build_deepseek_selection_prompt(self, selection_request: Any) -> str:
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"""
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为 DeepSeek 生成显式 JSON 输出提示。
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DeepSeek 官方文档要求在 JSON 输出模式下，提示词中必须明确包含 JSON
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约束，否则兼容端点可能返回空内容或无意义输出。
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"""
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return (
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f"{selection_request.system_message}\n\n"
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"Return the answer in JSON only.\n"
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'Use exactly this shape: {"tools": ["tool_name_1", "tool_name_2"]}\n'
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"Rules:\n"
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"- The `tools` field must be a JSON array of strings.\n"
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"- Only use tool names from the allowed list below.\n"
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"- Order tools by relevance, with the most relevant first.\n"
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"- Do not add explanations, markdown, or extra keys.\n\n"
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f"Allowed tools:\n{self._render_tool_list(selection_request.available_tools)}"
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)
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def _normalize_selection_response(self, response: Any) -> dict[str, list[str]]:
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"""
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解析并标准化 DeepSeek JSON 模式的工具筛选结果。
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"""
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content = getattr(response, "content", response)
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text = self._extract_text_content(content)
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payload = self._parse_json_object(text)
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tools = payload.get("tools")
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if not isinstance(tools, list):
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raise ValueError(f"工具筛选 JSON 缺少 `tools` 数组: {payload}")
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normalized_tools = [tool_name for tool_name in tools if isinstance(tool_name, str)]
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return {"tools": normalized_tools}
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async def _aselect_tools_with_deepseek(
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self, selection_request: Any
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) -> dict[str, list[str]]:
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"""
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使用 DeepSeek 兼容的 JSON 输出模式执行异步工具筛选。
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"""
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logger.debug("工具筛选走 DeepSeek JSON 兼容分支")
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structured_model = selection_request.model.bind(
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response_format={"type": "json_object"}
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)
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response = await structured_model.ainvoke(
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[
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{
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"role": "system",
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"content": self._build_deepseek_selection_prompt(
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selection_request
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),
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},
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selection_request.last_user_message,
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]
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)
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return self._normalize_selection_response(response)
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async def awrap_model_call(self, request: Any, handler: Any) -> Any:
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"""
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异步版本的 DeepSeek 工具筛选兼容分支。
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"""
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selection_request = self._prepare_selection_request(request)
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if selection_request is None:
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return await handler(request)
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if not self._is_deepseek_compatible_model(selection_request.model):
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return await super().awrap_model_call(request, handler)
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response = await self._aselect_tools_with_deepseek(selection_request)
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modified_request = self._process_selection_response(
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response,
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selection_request.available_tools,
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selection_request.valid_tool_names,
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request,
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)
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return await handler(modified_request)
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