[BUG] convertToModelMessages produces invalid ModelMessage[] when providerMetadata is present in UI text parts

[marinoska]

Describe the bug

Coming up with a quick fix.

Reported the problem details to Vercel AI.

We recently updated "ai" ti the latest and I think it is connected with this - I didn't notice that problem earlier.

Quick description

When using convertToModelMessages from the Vercel AI SDK, the function copies providerMetadata into providerOptions on text parts, causing the resulting output to be rejected by generateText() or streamText() with:

InvalidPromptError: The messages must be a ModelMessage[]. If you have passed a UIMessage[], you can use convertToModelMessages to convert them.

Quick fix

Strip the excessive fields (like providerOptions) right before passing ui messages to ai's convertToModelMessages

Steps To Reproduce

Connect to voltagent chat endpoint directly like below and enjoy that very server error after the first assistant response and the following up user message

  const { messages, sendMessage, stop, status, addToolResult } = useChat({
    transport: new DefaultChatTransport({
      api: `http://localhost:${port}/agents/${agentId}/chat`,
      prepareSendMessagesRequest({ messages }) {
        const input = [messages[messages.length - 1]];
        return {
          body: {
            input,
            options: {
              userId,
              conversationId,
              temperature: 0.7,
              maxSteps: 10,
            },
          },
        };
      },
    }),
    onToolCall: handleToolCall,
    onFinish: () => {
      console.log("Message completed");
    },
    onError: (error) => {
      console.error("Chat error:", error);
    },
    sendAutomaticallyWhen: lastAssistantMessageIsCompleteWithToolCalls,
  });

Expected behavior

no errors

Packages

• @voltagent/core

Additional Context

No response

[omeraplak]

Thank you @marinoska ⚡️