/**
 * detach/drivers/microtaskBatch.ts — Batch detached work into ONE microtask.
 *
 * Pattern:  Producer-consumer with batched flush. Same shape as
 *           agentfootprint's `EventDispatcher` flush queue and the React
 *           reconciler's microtask scheduling — accumulate during the
 *           current sync slice, drain at the next microtask boundary.
 * Role:     Default driver for in-process detach. Cheapest scheduling
 *           primitive on V8/JSC: one `queueMicrotask` per batch
 *           regardless of how many work items, so the perf budget
 *           amortizes. Suitable for browser AND node AND edge runtimes
 *           (queueMicrotask is universal since 2018).
 *
 * Lifecycle:
 *
 *   schedule(child, input, refId)            ← driver entry
 *     └─ create handle (queued)
 *     └─ register in detachRegistry
 *     └─ push work item onto local queue
 *     └─ if no microtask scheduled yet → queueMicrotask(flush)
 *     └─ return handle (sync — passive recorder rule)
 *
 *   flush() (microtask)                       ← deferred
 *     └─ swap out queue (drain races safely)
 *     └─ for each item: _markRunning, await runChild, _markDone/_markFailed
 *     └─ unregister handle from detachRegistry
 *
 * Why microtask (and not setImmediate / setTimeout):
 *   - Microtasks run BEFORE returning to the event loop — guarantees
 *     the work finishes within the current "tick" if the runtime allows
 *   - Lowest possible deferral cost (~50ns on modern V8)
 *   - Works in EVERY JS runtime (browser, node, deno, bun, edge)
 *   - Doesn't require any timer infrastructure → no GC pressure
 *
 * Re-entrancy:
 *   - If `runChild` calls `schedule()` for nested detach, the new item
 *     lands on the SAME queue. Because `scheduled` flips back to false
 *     at the start of `flush`, the new item triggers a fresh microtask.
 *   - Worst-case: O(n) microtasks for n nested levels. Acceptable —
 *     real-world detach trees are shallow.
 */
import { type ChildRunner } from '../runChild.js';
import type { DetachDriver } from '../types.js';
/**
 * Build a microtask-batch driver wired to a custom child runner. Most
 * consumers want the default singleton `microtaskBatchDriver` instead;
 * this factory exists for tests and for advanced consumers who want to
 * inject their own runner (e.g., a runner that wraps the child in a
 * tracing context).
 */
export declare function createMicrotaskBatchDriver(runChild?: ChildRunner): DetachDriver;
/**
 * Default singleton. Most consumers import this and pass it to
 * `executor.detachAndJoinLater(child, input, { driver: microtaskBatchDriver })`
 * (or rely on it being the executor's default driver, set in T5b).
 */
export declare const microtaskBatchDriver: DetachDriver;