ai/src/prompt/prompt.ts

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import type { ModelMessage, SystemModelMessage } from '@ai-sdk/provider-utils';

/**
 * Prompt part of the AI function options.
 * It contains a system message, a simple text prompt, or a list of messages.
 */
export type Prompt = {
  /**
   * System message to include in the prompt. Can be used with `prompt` or `messages`.
   */
  system?: string | SystemModelMessage | Array<SystemModelMessage>;

  /**
   * Whether system messages are allowed in the `prompt` or `messages` fields.
   *
   * When disabled, system messages must be provided through the `system`
   * option. When unset, system messages are allowed with a warning.
   *
   * @default undefined
   */
  allowSystemInMessages?: boolean;
} & (
  | {
      /**
       * A prompt. It can be either a text prompt or a list of messages.
       *
       * You can either use `prompt` or `messages` but not both.
       */
      prompt: string | Array<ModelMessage>;

      /**
       * A list of messages.
       *
       * You can either use `prompt` or `messages` but not both.
       */
      messages?: never;
    }
  | {
      /**
       * A list of messages.
       *
       * You can either use `prompt` or `messages` but not both.
       */
      messages: Array<ModelMessage>;

      /**
       * A prompt. It can be either a text prompt or a list of messages.
       *
       * You can either use `prompt` or `messages` but not both.
       */
      prompt?: never;
    }
);