/**
 * Claude Code hook I/O protocol. Hooks are spawned as subprocesses; they
 * receive a JSON envelope on stdin and may write a JSON decision on stdout.
 *
 * Reference: https://docs.claude.com/en/docs/claude-code/hooks (subject to
 * change; the fields below are what sigil's hooks read and write).
 */
export interface HookEnvelope {
    session_id?: string;
    transcript_path?: string;
    hook_event_name?: string;
    tool_name?: string;
    tool_input?: Record<string, unknown>;
    tool_response?: Record<string, unknown> | string;
    [key: string]: unknown;
}
/**
 * Decision emitted by a PreToolUse hook. Returning `{ decision: "block" }`
 * stops the tool call and surfaces `reason` to the model.
 */
export interface BlockDecision {
    decision: 'block';
    reason: string;
}
/**
 * Output from a PostToolUse hook that wants to modify the tool's response
 * (e.g., redact secrets). The exact shape Claude Code accepts is in flux;
 * we emit a structure that has been stable in recent versions.
 */
export interface PostToolModification {
    hookSpecificOutput: {
        hookEventName: 'PostToolUse';
        updatedToolResponse: Record<string, unknown> | string;
    };
}
/**
 * Read the entire stdin stream and parse it as JSON. Returns an empty
 * object if stdin closes without data.
 */
export declare function readHookEnvelope(stdin?: NodeJS.ReadableStream): Promise<HookEnvelope>;
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