State Taxonomy and Ownership Decision Framework Volume 06 - Professional Frontend | Phase 23
The first question is ownership, not API choice When developers ask "Should this use Context or Zustand?", they often skip the more important question: what kind of information is this, and which subsystem is already responsible for it?
React documentation emphasizes a single source of truth for each unique piece of state. That does not mean all application state belongs in one global location; it means each piece has one authoritative owner.
Does it come from the server?
YES NO YES TanStack Query Should the URL preserve it? URL state
Is it unsaved form input? Does only nearby UI need it?
YES YES NO React Hook Form useState/useReducer Context only if truly shared
Practical matrix Task rows Server state -> TanStack Query. Do not copy them into useState just to render them.
Search + page URL state -> searchParams/router because navigation, refresh, history, and sharing should preserve them.
Unsaved title Form state -> React Hook Form because it owns dirty/touched/errors/submission semantics.
Mobile menu Local UI state -> useState because it is ephemeral and belongs to one interaction open boundary.
Authenticated Supabase Auth. Other layers consume verified identity; they do not invent a second session session store.
Completed Task Derived state -> compute from authoritative data instead of storing a second count. count
Decision rule Choose the narrowest owner that can correctly preserve the state for the lifetime and scope it actually needs.
Authorization decides what an authenticated identity may do to a specific resource. UI hiding is never a substitute for server-side enforcement.
Restate the goal of “State Taxonomy and Ownership Decision Framework” as one observable behavior. Write the success signal before touching code.
Trace the boundary map: trusted identity → requested action → resource scope → policy decision → allow/deny. Mark the one boundary this lesson changes.
Inspect the current repository state and record the exact files, route, table, or runtime involved. Avoid creating an abstraction before you can name the existing owner.
Implement the smallest vertical slice. Add one coherent change, run the narrowest verification command, and read the output before continuing.
Connect the slice to TaskFlow’s phase artifact: A state ownership map for TaskFlow plus refactored examples removing redundant synchronized state.. Verify behavior from the outside as a user or API client would.
Create one controlled failure that is safe to reproduce. Predict the symptom first, capture evidence, locate the earliest broken boundary, then fix only that cause.
Close the reference and rebuild or explain the core change from memory. Record what you would monitor or test before trusting the same change in production.
const canEdit =
user.role === "ADMIN" ||
(user.role === "MEMBER" && task.ownerId === user.id);
if (!canEdit) throw new ForbiddenException();Do not copy this as a finished answer. Predict what each boundary does, type the smallest useful slice, run it, then compare the result with your prediction.
Trace verified identity, role, resource owner/workspace, and policy inputs separately.
Add server-side resource authorization; UI visibility is only experience, never enforcement.
Without copying the final source, create a second small scenario that applies “State Taxonomy and Ownership Decision Framework” to a different TaskFlow resource or input. Write the acceptance criteria first, implement it, and provide the evidence that each criterion is satisfied.
Inventory every state variable on one TaskFlow screen and classify it: server, URL, form, local UI, or cross-cutting client.
Use the smallest change that demonstrates this lesson. Stop after it works and capture evidence.useEffect syncing query data into local state
Predict the symptom before causing the failure. Then locate the earliest boundary where reality diverges from expectation.Why does this responsibility live here, what input does it trust, what output proves success, and what would go wrong if another layer owned it?
If your explanation is vague, repeat the boundary trace before moving on.Close the reference. Reproduce the core idea from memory or explain the exact request/data flow aloud. Then check your diff or notes for accidental shortcuts that bypass validation, authorization, error handling, or verification earned in earlier phases.