/**
 * Generic config-dir synthesis (layer C) — the SINGLE deep-merge / union /
 * symlink implementation for all harnesses (see the `harness-config-dir`
 * capability). A harness declares its shape via `HarnessConfigProfile`
 * (`src/harness/interface.ts`); this module does the filesystem work so the
 * merge algorithm lives in exactly one place.
 *
 * Two modes:
 * - `layer` (default): synth dir = deep-merge of base ⊕ overlay
 *   (`mergeFiles` deep-merged, overlay keys win, arrays replaced wholesale;
 *   `unionDirs` unioned, overlay wins on name clash; `authFiles` symlinked FROM
 *   base). Synth dirs live under `<hostStorage>/tmp/subagents/<parent>/<agent>`
 *   — the same location and lifecycle as pi's per-spawn config, so
 *   `subagent-teardown.ts` already scopes there.
 * - `replace`: no synthesis — resolve straight to the user's dir; nothing is
 *   copied and teardown skips it.
 *
 * Host-neutral: no pi package imports (enforced by
 * `test/host-import-boundary.test.ts`).
 */
import type { HarnessConfigProfile } from "#src/harness/interface";
export type ConfigDirMode = "layer" | "replace";
export interface SynthesizedConfigDir {
    /** The dir the harness's CLI is pointed at (the redirect target). */
    dir: string;
    /** The env assignment that points the harness at `dir` (`redirectEnv`). */
    env: Record<string, string>;
}
/** Identity of the spawn, used to place the per-spawn synth dir. */
export interface SynthIds {
    parentId: string;
    agentId: string;
}
/**
 * Base dir under which every per-agent synth config dir lives. MUST match
 * `subagentsBaseDir()` in `src/subagent-teardown.ts` so layer synth dirs are
 * torn down, and pi's `createSubagentConfig` location so no-override pi output
 * is byte-for-byte unchanged.
 */
export declare function synthConfigDirRoot(ids: SynthIds): string;
/**
 * Deep-merge two JSON objects: overlay keys win; nested plain objects are
 * merged recursively; arrays (and scalars) are replaced WHOLESALE (not
 * element-merged), matching the guard `turnThresholds` precedent.
 */
export declare function deepMergeJson(base: Record<string, unknown>, overlay: Record<string, unknown>): Record<string, unknown>;
/**
 * Union a directory base ⊕ overlay into the target: symlink each top-level
 * entry from base, then from overlay (overlay wins on name collision). Skips a
 * side that does not exist. Nothing written when neither side exists.
 */
export declare function unionDir(baseDir: string, overlayDir: string, targetDir: string): void;
/**
 * Provide an auth file in the synth dir FROM the base (symlink by default).
 * No credential duplication; read-only. Skips a base file that does not exist.
 */
export declare function provideAuth(baseFile: string, targetFile: string): void;
/**
 * Synthesize (layer) or resolve (replace) the config dir for a harness.
 *
 * @param profile   The harness's declarative config-dir shape.
 * @param overlayDir The user-supplied config dir (layer overlay / replace target).
 * @param mode      "layer" (deep-merge base ⊕ overlay) or "replace" (dir as-is).
 * @param ids       Spawn identity, for the per-spawn synth dir location.
 */
export declare function synthesizeConfigDir(profile: HarnessConfigProfile, overlayDir: string, mode: ConfigDirMode, ids: SynthIds): SynthesizedConfigDir;
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