# Exact identity + versioned membership

Keep the exact versions and ordered History membership an AgentCore application needs separate from how each view displays them.

Status: Implemented in source. Prelaunch; not a live service guarantee.

Reviewed: 2026-10-14.
Backend source: e16b81b4a637acec91f3aed8a71cf5b0f42f0c19.
Native toolkit: merged in PR #176, reviewed at e16b81b4a637acec91f3aed8a71cf5b0f42f0c19.
HTML: /docs/primitives

## In short

Give an AgentCore application exact references it can inspect later. allIds() fixes the ordered History membership; byIds() fetches precisely those retained revisions. The graph, timeline and comparison are views over those answers, without running the original agent or tool.

**Available today:** These methods implement the bounded History contract. General collections and arbitrary payload queries are not implied.

> Give an AgentCore application fixed History membership and exact retained versions.

## Two primitives beneath the workspace

- **allIds()** — Fix the ordered History references for the application's read.
- **byIds()** — Fetch exactly the retained revisions that membership names.
- **Views** — Use graph and timeline to inspect those answers without rerunning AgentCore work.

## allIds() fixes membership

A bounded day generation names ordered exact revision references. Preserve the returned generation and cursor while paging; a late arrival belongs to a successor generation rather than silently changing the collection being read.

The broader platform reuses this normalized-state idea, but the existing allIds() API keeps its exact History contract rather than becoming a generic dependency endpoint.

## byIds() hydrates exactly what was named

Hydration restores caller order and reports found, unresolved, unavailable and expired positions explicitly. It does not replace an unavailable historical revision with the latest value.

Stable identity plus immutable revisions makes a later diff inspectable: unchanged references can be structurally shared while changed membership becomes an explicit input to reconciliation.

## Exact reads depend on the contract

The value comes from the contract: stable logical identity, immutable revision identity, ordered bounded membership, generation pinning, correction rules, authorization, retention and recovery.

That foundation can support exact checkpoints, replay, State and Context profiling and turn-to-turn change explanations without making probabilistic retrieval the source of operational truth.

[Read State reconciliation](/docs/state)

[See the exact History example](/?capability=workflows#trajectory)