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Graph/host-state-mutated-list-desync

Pattern

Host-State Desync & Selection

host-state-mutated-list-desync

Mutable host-side state gets applied across shared scopes (selection lists or replicated collections) so actions in the same tick can land out of order, causing wrong targets like “sold the wrong sword” and selection-driven edits affecting multiple objects.

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Public graph metadata

Updated8/6/2026

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30 linked nodes

the UI doesn’t update consistently, sometimes the count lags behind — when using useTransition. Tension: especially after fast re-renders or route changes. Outcome: Zustand state and Server Actions transitions aren’t syncing properly in React’s concurrent rendering mode.

Changing the language in one select box updates the page translation, but the other select box keeps the previous language value instead of reflecting the new language from the zustand store.

Pointer/mouse handlers in a React + PIXI canvas use stale Zustand state, causing dragging/editing of sequence points to behave incorrectly. The issue persists when state is modified during mouse up, and recreating handlers inside effects/updates prevents some but not all bugs (e.g., cannot drag twice).

Storing a huge state object (e.g., an array of complex objects like Tiptap editors) in Zustand led to performance issues.

Using multiple shadcn `Toggle` components to implement a single-select stroke toggle set does not reliably keep only one toggle active and visually in sync with React state.

Using a Zustand store to control TanStack Table v8 state causes errors because the table calls change handlers with an updater function, but the store setters only accept raw values.

parallel workers sometimes grab overlapping sets, then wait to mark them as being processed — At the time of item selection, you neither lock them nor check whether they're locked. Tension: someone else could've already grabbed a subset of those. Outcome: duplicate their work on the items they happened to share.

job status stored in one handler is not visible in the waiting code

On a self-hosted GitHub Actions runner, jobs intermittently get stuck in the queued state and do not start even though the runner is online and idle. This happens randomly on various workflow steps/jobs.

an error occurs when the event is "user-changed-channel" — I'm trying to change state using dispatch(). Tension: `const obj = { ...state.channels }` only shallow copies the references into a new object reference. Outcome: You must use immutable state updates that shallow copy all state, and nested state, that is being updated.

Storybook conditional controls that are hidden based on another arg do not update the underlying args store, leading to an invalid props/type state (TypeScript invariant break). Saving changes also fails to preserve the component prop type interface, where `undefined` values cannot be reliably serialized/merged.

Changes to a shared mutable object may never become visible to another thread

JCStress reports FORBIDDEN outcomes (state marked finished but operation result not recorded) when using two identical reader actors, even though the same behavior with a single reader actor produces only ACCEPTABLE results.

do my fences interrupt other guests on the machine? — running in a VM on a cloud provider. Tension: If not, how's that possible since this is an op implemented in hardware and not software? Outcome: Fences are local, affecting only the current thread.

developers are unsure which [Sync] flags to use and when — In s&box multiplayer. Tension: Without the right flags, values either don't replicate or replicate from the wrong authority.

calling [Rpc.Host] from a client does nothing, calling [Rpc.Broadcast] from a client doesn't work as expected, or RPCs fire on the wrong machine — In s&box multiplayer. Tension: The three RPC types have distinct call semantics that differ from Unity's Command/ClientRpc model.

The s&box SaveSystem diffs the current scene JSON against a baseline to produce a patch. Tension: After loading a save, these values revert to defaults, causing desync between what was saved and what is restored. Outcome: health, ammo, custom networked state.

Developers building NPCs in s&box often use monolithic Update() methods with complex state machines. — in s&box. Tension: This becomes hard to extend and debug. Outcome: A task/schedule pattern provides clean separation of NPC behaviors.

Common mistakes: (1) not calling RemovePlayer on disconnect causing memory leaks, (2) unbounded stack growth, (3) broadcasting undo notices to all players instead of just the owner, (4) not removing objects from undo stacks when they're picked up — Sandbox-style games need per-player undo stacks. Tension: allowing players to undo weapons out of other players' hands.

animate on the client only (causing desync) or use Lerp-based rotation — Developers building interactive doors in s&box. Tension: doesn't support custom easing. Outcome: The correct pattern syncs state and time, uses AnimationCurve for easing, and routes all state changes through the host.

SkinnedModelRenderer morph values in s&box are not automatically persisted in dupes or saves — and are not synced over the network. Tension: Developers who set morphs directly lose them on dupe/save/load and new clients don't see them. Outcome: developers who set morphs directly lose them on dupe/save/load and new clients don't see them.

Projectile hit detection in s&box needs to run on the host only, ignore the instigator — Projectile hit detection in s&box. Tension: use ICollisionListener (not trigger volumes). Timed explosives need host-authoritative detonation using TimeSince rather than async delays.

World-space camera shake (explosions, earthquakes) in s&box needs to respect distance falloff, user screenshake preferences, and use smooth noise rather than random values. Tension: Sending UI notices to specific players requires Rpc.FilterInclude. Outcome: Sending UI notices to specific players requires Rpc.FilterInclude.

recreate schedule/behavior objects every tick — Developers building NPCs in s&box. Tension: causing allocations. Outcome: The correct pattern caches schedules by type and reuses them, only reinitializing when a new schedule is selected.

the operation's side effect doesn't record that it has already occurred — Idempotency Domain. Tension: re-execution produces duplicate effects.

developers don't know what state survives a hotload, what gets reset, and how to write hotload-safe code — In s&box, hotloading (live code reload without restarting the game) works automatically during development. Tension: Static fields survive hotloads but component state is re-initialized.

Features built on optional capabilities silently degrade across the client matrix. Outcome: Community 4's transport bugs and Community 103's capability detection failures are two symptoms of the same architectural constraint.

naive optimistic updates either (a) flicker because the next server [REDACTED]shot wipes them or (b) get stuck because you can't — In a server-authoritative realtime app (game tick, collaborative doc). Tension: the next server [REDACTED]shot wipes them. Outcome: Switching to derive-from-[REDACTED]+[REDACTED] made the whole thing trivially correct.

when the server mutates the list. Tension: they only happen when two actions land in the same tick. Outcome: you get 'sold the wrong sword' bugs that are infuriating to reproduce.

Adding fields to a persisted player/document schema breaks loading of older saves — single-writer file-backed store. Outcome: every read produces a current-shape object.

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