/**
 * Graph Model v2 — Data Passthrough Transform
 *
 * Version: 2.0
 * Date: 2026-07-25
 *
 * Pure, side-effect-free application of an edge's `data_passthrough`
 * ({@link DataMapping}) to an {@link EdgePayload} before it is handed
 * downstream. The engine calls this once per activating edge so each
 * downstream edge can reshape the same upstream result independently.
 *
 * Semantics:
 *   - `maxChars` truncates `payload.result` to at most N characters.
 *   - `exclude` removes artifact paths whose full path or basename matches an
 *     excluded name, and — when `payload.result` is parseable JSON — drops the
 *     matching top-level keys from the JSON object.
 *
 * The module holds no state and mutates nothing: a payload that needs no
 * transformation is returned by reference (identity preserved); a payload that
 * does need a transformation is cloned shallowly first.
 *
 * Design reference: .rolebox/design/tool-merge-map.md §2.2 (data_passthrough).
 */
import type { EdgePayload } from "../../types.engine-v2.ts";
import type { DataMapping } from "../../types.graph-v2.ts";
/**
 * Apply an edge's {@link DataMapping} to an upstream payload.
 *
 * Application order (each step operates on the output of the previous):
 *   1. `fields` (include whitelist) — when non-empty, keep only the
 *      whitelisted top-level keys from `payload.result` (parsed as JSON).
 *      Non-JSON / non-object results pass through unchanged.
 *   2. `exclude` — strip matching top-level JSON keys and artifact paths.
 *   3. `maxChars` — truncate `payload.result` after both key-level
 *      transforms have been applied.
 *
 * A `mapping` that is undefined or carries no applicable field is a no-op and
 * returns the payload by reference. Otherwise the payload is shallow-cloned and
 * its `result` (whitelisted / key-stripped / truncated) and `artifacts`
 * (filtered) are updated. `fromNode`, `fromSignal`, and `budgetConsumed` are
 * untouched.
 *
 * @param payload - the upstream {@link EdgePayload}.
 * @param mapping - the edge's data passthrough mapping (optional).
 * @returns the transformed payload (a clone when a change applied, otherwise
 *   the same reference).
 */
export declare function applyDataMapping(payload: EdgePayload, mapping?: DataMapping): EdgePayload;
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