Isolation

Two unkeyed sibling components that provably cannot re-render each other: Deja state notifies exactly one listener — its owning component.

Sibling components cannot cross-render

Component A renders: 3

State IsLoading IsReFetching IsError IsCachedData IsStale ReFetchCount: 1

#1 — delectus aut autem

Component B renders: 3

State IsLoading IsReFetching IsError IsCachedData IsStale ReFetchCount: 1

#2 — quis ut nam facilis et officia qui

Each panel owns its own unkeyed Query<T>. Reloading one advances its render counter while the other's stays frozen — Deja state notifies a single attached listener, and that listener is the owning component. 

<div class="demo-panels">
    <IsolationPanel Title="Component A" TodoId="1"/>
    <IsolationPanel Title="Component B" TodoId="2"/>
</div>

<p class="demo-note">
    Each panel owns its own unkeyed <code>Query&lt;T&gt;</code>. Reloading one advances its render
    counter while the other's stays frozen — Deja state notifies a single attached listener, and
    that listener is the owning component.
</p>

Why this matters#

Event- or store-based state managers broadcast: one component's refresh marches every subscriber through a re-render. Deja's IDejaObservable holds a single listener slot — attaching a second listener throws, and the one listener is the owning component. The render counters make the guarantee observable: reload panel A as fast as you like, panel B's counter never moves.

Sharing without coupling#

When two components should share data, don't share the query — share the cache entry by using the same key (see the shared cache demo), or pass Data down as a [Parameter]. Both paths keep ownership single and renders scoped.