/**
 * System Prompt Override
 *
 * Handles CLI flags for replacing or appending to the system prompt:
 * - --system-prompt <text>         → replace entire prompt
 * - --system-prompt-file <path>    → replace from file
 * - --append-system-prompt <text>  → append text to default prompt
 * - --append-system-prompt-file <path> → append file contents
 */
export interface OverrideOptions {
    /** Replace the entire system prompt with this text */
    systemPrompt?: string;
    /** Replace the entire system prompt with contents of this file */
    systemPromptFile?: string;
    /** Append this text to the default system prompt */
    appendSystemPrompt?: string;
    /** Append contents of this file to the default system prompt */
    appendSystemPromptFile?: string;
}
export declare class SystemPromptOverride {
    /**
     * Apply override options to a base system prompt.
     *
     * - If systemPrompt or systemPromptFile is set, the base prompt is REPLACED.
     * - If appendSystemPrompt or appendSystemPromptFile is set, content is APPENDED.
     * - Cannot use both replace and append simultaneously.
     * - If no overrides, returns the base prompt unchanged.
     */
    apply(basePrompt: string, options: OverrideOptions): string;
    /**
     * Read a file from disk. Throws if the file does not exist.
     */
    private readFile;
}
