If the request fails, the previous message is not restored

[AntzyMo]

Description

If steamText encounters an error, messages of useChat will lose the messages sent by user due to error reporting. For example:

const messages = [
    {
        "role": "user",
        "content": "hi"
    },
    {
        "role": "assistant",
        "content": "hello"
    },
    {
        "role": "user",
        "content": "who are you?"
    }
]

If you send the last item of the messages array and an error is reported, the message who are you will be displayed. I think this is wrong and it looks like a bug.

So my idea is to restore to the previous message when an error is reported, including user

Code example

ai/packages/vue/src/use-chat.ts

Line 128 in a92523c

const previousMessages = messagesData.value;

Taking vue as an example, previousMessages should be changed to const previousMessages = messagesSnapshot, which can ensure the latest message records

Additional context

No response

[lgrammel]

Note: this came up internally as well.

[jh3y]

Yep - This one gives the developer a little more work to do with the out of the box behavior.

Consider:

1. Start a new chat
2. Enter question
3. System errors
4. Wipes UI including users' question

The current workarounds rely on the developer maintaining a second shadow state of the AI state in order to provide better UX to their users.

In most cases, although the error message is most likely generic and related to the server itself, the user probably expects an error message in place of the streaming message coming in or appended to it with the option to reload or trigger a new message.

[lgrammel]

#2262