Concurrent set execution sequencing in Zustand stores with async middleware

This question investigates the defined execution order when multiple set operations are issued concurrently within a Zustand store, particularly when async middleware such as persist is active. The goal is to clarify whether call sequencing is deterministic, and how shallow merge semantics interact with interleaved asynchronous side effects.

Relevant constraints include Zustand's default shallow merge behavior, which may overwrite nested state properties without Immer integration, and the store's closure-based subscription model that does not guarantee ordering across simultaneous dispatches. Version assumptions are based on Zustand v4.x, where middleware interception points remain an area of practical uncertainty.

• What precedence rule, if any, governs the order of state updates when two set calls overlap within the same microtask?
• Does async middleware intercept and reorder calls, and if so, how does that affect the final store state?
• Can developers rely on a consistent execution sequence for side-effect coordination, or is the behavior release-dependent?