Documentation: 0.5.0 (source: v0.5.0).
# Subscriptions

> Live account updates, reconnection, and cancellation.

Markdown source of https://docs-v0-5-0.atlas-kit-docs.pages.dev/concepts/subscriptions/ — see https://docs-v0-5-0.atlas-kit-docs.pages.dev/ai/ for the full machine-readable surface.

Polling works, and for most applications it is enough. When it is not, the
context can subscribe to account updates instead.

Subscriptions are **context-owned**, which is the important detail: an update
arriving over a subscription goes through the same validation and lands in the
same cache as a normal read. A subscribed fleet and a fetched fleet are the
same cached snapshot, not two views that can disagree.

## What that buys you

Without shared identity, a live update and a fetch race each other, and which
one your application sees depends on timing. Here they cannot diverge: both
write to the same cache slot under the same key.

Updates are translated the same way reads are, so a subscription delivers the
SDK's own snapshot types rather than raw account bytes.

## Reconnection

Connections drop. When one does, the SDK resynchronises rather than resuming
blindly, because the gap between disconnect and reconnect is exactly where
missed updates hide.

Reconnects coalesce: a burst of drops produces one resynchronisation rather
than one per drop, and a reconnect that arrives while another is in flight is
folded into it rather than queued behind it.

## Cancellation

Subscriptions are cancellable, and disposing a context cancels everything it
owns. That matters in a browser, where a component unmounting must not leave a
socket delivering updates into a cache nobody reads.

## When to reach for this

Prefer polling with a sensible `maxAge` unless you have a reason not to. It is
simpler, it degrades more gracefully, and for state that changes on the scale
of minutes it is indistinguishable to a user.

Subscribe when you are tracking something that genuinely moves — an active
fleet, an order book — and staleness is visible.

## Reference

- [`client`](/reference/client/) — subscription exports
- [Caching and provenance](/concepts/caching/) — the cache updates land in