Interface StreamChunk

interface StreamChunk {
    delta: string;
    finishReason?: FinishReason;
    parentSpanId?: string;
    runId?: string;
    spanId?: string;
    toolCall?: ToolCall;
    toolResult?: ToolCallResult;
    type?: "model_delta" | "tool_call" | "tool_result" | "final";
    usage?: { completion: number; prompt: number; total: number };
}