import type { TaskSpec } from "./types.js";
/** Thrown when `overrides` would LOOSEN a safety field `base` already set (a tighten-only violation). */
export declare class TaskSpecTightenError extends Error {
    constructor(message: string);
}
/**
 * Merge `overrides` onto `base` with TIGHTEN-ONLY semantics for the safety-bearing fields. Non-safety fields
 * follow plain last-wins object spread (`overrides` value wins when present, else `base`). The safety fields
 * get explicit rules:
 *
 *  - **`toolPolicy`** — both set ⇒ `combinePolicies(base, override)` (deny-wins; the base's denials survive,
 *    the override can only ADD denials/asks). Either alone ⇒ that one. This is the central fix: a blind spread
 *    would drop the base policy entirely.
 *  - **`handsReadOnly`** — `true` is stricter. `base:true` + `override:false` ⇒ **throw** (loosening). Otherwise
 *    the stricter (`true` if either is true) wins.
 *  - **`shellGate`** — `off < classify < always`. `override` may only equal-or-raise the rank; lowering it ⇒
 *    **throw**. The stricter of the two wins.
 *  - **`onAsk`** — no safe automatic merge (the approver and the policy must be coordinated). Both set to
 *    DIFFERENT values ⇒ **throw**; equal ⇒ keep; one set ⇒ that one.
 *  - **`hooks`** — no standard composition (stacking hook results is caller-specific). Both set ⇒ **throw**;
 *    one set ⇒ that one.
 *
 * @throws {TaskSpecTightenError} when an override would loosen a stricter base safety field, or when two
 * incompatible safety values are both set and cannot be merged automatically.
 */
export declare function tightenTaskSpec(base: TaskSpec, overrides: Partial<TaskSpec>): TaskSpec;
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