Agent Writer Reorder Gap Buffer

Reorders out-of-order events from multiple concurrent writer instances into each instance's contiguous sequence -- buffering events that arrive ahead of a gap, dropping true duplicates, and refusing to splice a crashed-and-respawned writer's old and new incarnations into one fake-clean log. No I/O, no clock, no network: a pure in-memory state machine over events you already have.

THE SILENT FAILURE. Concurrent writers append to a shared log and their events arrive interleaved and out of order. Sorting by sequence number per writer looks like the fix, and it is -- right up to the moment a writer crashes and respawns. The new incarnation starts its sequence again from a low number, those events sort in among the old incarnation's, and the result is a log with no gaps and no duplicates that describes a history that never happened. Nothing throws. The log's own cleanliness is what hides it, which is why this is worth checking rather than assuming.

INSTANCE IDENTITY IS PART OF THE KEY, NOT AN AFTERTHOUGHT. Ordering is per (writerId, instanceId), so two incarnations of the same writer can never be merged. A gap is reported as a gap and held, rather than closed by whatever arrives next.

WHAT VERIFICATION CHANGED. A rival implementation built from the README failed fifteen tests -- by far the most in the batch -- and the suite was RIGHT every time. The failures were real contracts that the README had left implicit: that the returned event is the same object you passed in, identical by Object.is rather than a copy, and that the cascaded array is always present rather than sometimes absent. Callers depend on both. The README now documents the result contract explicitly and all 117 tests stand unchanged. Under-documentation, found and closed by someone trying to rebuild it from the docs alone.

VERIFIED: 117 tests, measured by running the suite, every mutation observed FAILING before restore.

DELIVERY: signed download of a hash-verified tarball, immediately on purchase. Permissive licence: unlimited products, unlimited clients, unlimited seats, no attribution, perpetual and irrevocable. One restriction, do not republish the source as source.

Interface

What you call, and what comes back. Types and signatures only — the implementation ships with the source.

  export function isNonEmptyString(value: unknown): value is string;
  export function isValidSeq(value: unknown): value is number;
  export function validateEvent(raw: unknown): RejectReason | null;