VertexAI, hit "System messages are only permitted as the first passed message."

[kphk]

When using VertexAI, I hit "System messages are only permitted as the first passed message." at node_modules/@langchain/google-common/dist/chat_models.js:77:27

It seems google assuming "system" type message can only be the first message.
Current simple workaround to filter out SYSTEM type message in conversations:

export class VertexAI2 extends VertexAI {
    async runQuery(system: string, userQuery: string, supportingContext: any[], pastConversations: any[]): Promise<string> {
        return super.runQuery(system, userQuery, supportingContext, pastConversations.filter((c: any) => c.sender !== 'SYSTEM'));
    }
}

Sure there should be a better solutions.