> ## Documentation Index
> Fetch the complete documentation index at: https://langchain-zh.cn/llms.txt
> Use this file to discover all available pages before exploring further.

# MESSAGE_COERCION_FAILURE

当消息对象不符合预期格式时，会发生此错误。

## 接受的消息格式

LangChain 模块接受 `MessageLikeRepresentation`，其定义如下：

```python theme={"theme":{"light":"catppuccin-latte","dark":"catppuccin-mocha"}}
from typing import Union

from langchain_core.prompts.chat import (
    BaseChatPromptTemplate,
    BaseMessage,
    BaseMessagePromptTemplate,
)

MessageLikeRepresentation = Union[
    Union[BaseMessagePromptTemplate, BaseMessage, BaseChatPromptTemplate],
    tuple[
        Union[str, type],
        Union[str, list[dict], list[object]],
    ],
    str,
]
```

这包括 OpenAI 风格的消息对象（`{ role: "user", content: "Hello world!" }`）、元组以及纯字符串（这些会被转换为 [`HumanMessage`](https://reference.langchain.com/python/langchain-core/messages/human/HumanMessage) 对象）。

如果模块接收到不属于这些格式之一的值，你将收到错误：

```python theme={"theme":{"light":"catppuccin-latte","dark":"catppuccin-mocha"}}
from langchain_anthropic import ChatAnthropic

uncoercible_message = {"role": "HumanMessage", "random_field": "random value"}

model = ChatAnthropic(model="claude-sonnet-4-6")

model.invoke([uncoercible_message])
```

```text theme={"theme":{"light":"catppuccin-latte","dark":"catppuccin-mocha"}}
ValueError: 消息字典必须包含 'role' 和 'content' 键，但收到 {'role': 'HumanMessage', 'random_field': 'random value'}
```

## 故障排除

要解决此错误：

1. **确保格式正确**：聊天模型的所有输入必须是 LangChain 消息类的数组或受支持的消息类格式
2. 验证你的消息没有发生意外的字符串化或转换
3. 检查错误的堆栈跟踪，并在消息传递给模型之前添加日志语句来检查消息对象

***

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