Scheduler and timing: The first run of an effect is deferred

The first run of an effect is deferred

useEffect and onMount are queued when created; their first run happens in the next flush, not at the call site.

For agentsUpdated 2026-10-20

useEffect and onMount are queued when created; their first run happens in the next flush, not at the call site. A render effect (what the compiler emits for DOM bindings) runs its first time immediately.

Effects never run on the server: useEffect, useRenderEffect and onMount return without creating a node when isServer is true.