[Bug]: Gemini 无法调用工具，需要思路签名 Function call is missing a thought_signature in functionCall parts.

[Sansui233]

Runtime environment

v4.6.5, Ubuntu 22, Native

Exception

如题，gemini-3-flash-preview 调用工具需要指定思路签名
see https://ai.google.dev/gemini-api/docs/thought-signatures?hl=zh-cn

[01-01 05:58:58.740] process.py (39) - [INFO] : Processing request from person_1847732214 (227): 你好 搜索一下今天的日期
[01-01 05:58:59.646] chat.py (130) - [INFO] : Conversation(227) Response: Call tool: function-...
[01-01 05:59:00.642] chat.py (130) - [INFO] : Conversation(227) Response: tool: "## Result 1: ...
[01-01 05:59:00.849] chat.py (143) - [ERROR] : Conversation(227) Request Failed: RequesterError 模型请求失败: 请求参数错误: Error code: 400 - [{'error': {'code': 400, 'message': 'Function call is missing a thought_signature in functionCall parts. This is required for tools to work correctly, and missing thought_signature may lead to degraded model performance. Additional data, function call `default_api:tavily_search` , position 6. Please refer to https://ai.google.dev/gemini-api/docs/thought-signatures for more details.', 'status': 'INVALID_ARGUMENT'}}]
[01-01 05:59:01.146] pipelinemgr.py (153) - [ERROR] : 模型请求失败: 请求参数错误: Error code: 400 - [{'error': {'code': 400, 'message': 'Function call is missing a thought_signature in functionCall parts. This is required for tools to work correctly, and missing thought_signature may lead to degraded model performance. Additional data, function call `default_api:tavily_search` , position 6. Please refer to https://ai.google.dev/gemini-api/docs/thought-signatures for more details.', 'status': 'INVALID_ARGUMENT'}}]

Reproduction steps

No response

Enabled plugins

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[dosubot]

Hi @Sansui233! I'm Dosu and I’m helping the LangBot team.

这个报错是因为 Gemini API 的工具调用（function call）现在强制要求每个 functionCall 里包含 thought_signature 参数，否则会返回 400 错误并导致工具无法正常调用，性能也会下降。thought_signature 是 Gemini 用来追踪和优化模型思考过程的元数据，具体结构和用途可以参考 官方文档。

目前 LangBot 的 Gemini 请求构造逻辑（GeminiChatCompletions 类）没有自动生成或注入 thought_signature 字段，导致请求参数不完整。你需要在构造 Gemini 工具调用请求时，按照 Gemini API 的要求，在每个 functionCall 的 parts 里补充 thought_signature 字段。建议在 GeminiChatCompletions._closure_stream 或相关工具列表生成逻辑里，给每个工具/函数加上类似如下结构：

tool_call = {
    "function": {
        "name": tool_name,
        "arguments": tool_args,
        "thought_signature": "your_signature_here"  # 具体内容见官方文档
    },
    "id": tool_id,
    "type": "function"
}

具体 thought_signature 的生成方式和内容建议参考 Gemini API 文档，通常可以用模型推理链的摘要或唯一标识符。

修复建议：在 Gemini 请求参数组装阶段（如 _closure_stream 方法），确保每个工具调用都包含 thought_signature 字段，否则 Gemini 工具调用会失败。相关代码参考

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