/** Structural mirror of `TaskState` in the plan store; kept here to avoid a cycle. */
export type TaskState = "pending" | "in_progress" | "done" | "failed" | "skipped";
export type TaskTransitionDenialCode = "terminal" | "retry-required" | "unsupported";
export interface TaskTransitionDenied {
    readonly allowed: false;
    readonly code: TaskTransitionDenialCode;
    readonly reason: string;
}
export type TaskTransitionResult = {
    readonly allowed: true;
} | TaskTransitionDenied;
/** True when no ordinary `task.update` may move the task any further. */
export declare function isTerminalTaskState(state: TaskState): boolean;
/**
 * Decide whether `task.update` may move a task from `from` to `to`.
 * Re-asserting the current state is always allowed so idempotent retries and
 * note-only updates keep working.
 */
export declare function evaluateTaskTransition(from: TaskState, to: TaskState): TaskTransitionResult;