Everything you don’t have to think about every day -- anymore.
Daily product work starts with business needs - not technical wrangling.
- 5
- explicit boundaries
- 2
- replaceable adapters
- 1
- policy authority
Explore the source by responsibility.
Select a layer to see what it owns, why the boundary exists, and the code that implements it.
The component describes what the user asked for. It never imports Supabase, constructs database records, or decides whether a transition is allowed.
1type View = "releases" | "onboarding";2 3const releaseActions: Partial<Record<4 ReleaseStage,5 { label: string; stage: ReleaseStage }[]6>> = {7 building: [{ label: "Start validation", stage: "validating" }],8 validating: [9 { label: "Mark ready", stage: "ready" },10 { label: "Block release", stage: "blocked" },11 ],12 blocked: [{ label: "Resume validation", stage: "validating" }],13 ready: [{ label: "Reopen validation", stage: "validating" }],14};Trace a mutation end to end.
The happy path and failure path use the same six steps. Select a step to inspect its owner, recovery contract, source, and reusable guidance.
Intent
Action contractsAllowed actions come from typed stage-to-action maps. The component emits a domain-shaped command and owns only transient feedback.
Unsupported transitions never appear as controls, and pending mutations disable repeated submission.
Understand the system before you assemble the screen.
A component library is the shared interface contract between design and product code. It turns recurring visual, interaction, responsive, and accessibility decisions into named parts that teams can inspect, reuse, and improve once.
Semantic tokens update every participating component without rewriting each feature.
Focus, disabled, loading, error, and responsive behavior travel with the component contract.
Design, engineering, QA, and agents refer to the same component, variant, and state names.
Components own presentation. Product callers retain data, policy, navigation, and mutations.
See the component. Then inspect the contract.
Select a library item and a meaningful state. The stage renders shared primitives and representative compositions; the contract explains what belongs in the library, what remains with the product, and when the abstraction earns its place.
Button
Expresses action hierarchy while preserving keyboard, disabled, and pending behavior.
Ready for human input.
- PUBLIC API
tone, disabled, type, onClick, children- SEMANTIC TOKENS
- Primary action, focus ring, control height, radius
- COMPONENT OWNS
- Visual hierarchy, focus treatment, disabled appearance, hit area.
- PRODUCT OWNS
- Permission, mutation, loading truth, confirmation, analytics.
- USE WHEN
- A person can initiate an action in the current context.
- AVOID WHEN
- Navigation to another page. Use a link with link semantics instead.
<Button tone="primary" disabled={saving}>
{saving ? "Saving…" : "Save changes"}
</Button>Adopt the library without stopping product work.
Start with the pieces already repeated in real screens. Move from leaves to patterns, and keep product behavior outside the visual contract.
- 01Inventory real screens
Find repeated actions, fields, status treatments, and panels. Capture every meaningful state before extracting anything.
- 02Map intent to tokens
Replace raw values with semantic roles such as primary action, supporting text, panel, success, and danger.
- 03Replace from the leaves up
Adopt primitives first, then compositions. Keep API calls, domain policy, permissions, and routing in the caller.
- 04Prove the contract
Exercise keyboard behavior, loading and failure states, content pressure, mobile widths, and representative production consumers.
Every new screen starts from tested decisions.
The team spends review time on the product problem instead of rediscovering button hierarchy, focus behavior, error placement, spacing, and responsive rules. Improvements flow back to every consumer through a small, typed API.
- Visual rules are copied into features
- States appear late during QA
- Design and code use different names
- Fixes stop at one screen
- Intent selects a known component
- States are part of the contract
- Tokens connect design and code
- Fixes improve every consumer
The full catalog lets you swap semantic tokens and inspect the hierarchy. The installable Design System skill explains how to extend it safely.
Put each kind of state where it can stay correct.
Use component state for transient interaction, the URL for shareable navigation, Context for stable subtree coordination, TanStack Query for server snapshots, and the service plus database for durable truth.
Open menu, draft input, hover, unsaved step
useState / useReducerSelected account, filters, tab, pagination
searchParamsTheme, current workspace, compound workflow dispatch
context + reducerPoints, releases, messages, document metadata
TanStack QueryAuthorization, revisions, policy, canonical writes
API + SupabaseSix hard cases, traced across real product surfaces.
Select a scenario to see its owner, synchronization path, failure contract, pattern, antipattern, and implementation sketch.
Points update everywhere
A reward earned on one page must update the top bar, account page, and open dialogs without copying the balance into three stores.
A shared balance changes across two surfaces
740
Available points
- Canonical owner
- TanStack Query cache
- Synchronization
- Optimistic mutation → API → canonical response
- Failure protection
- Cancel, snapshot, rollback, invalidate
Every surface reads the same ['account', id] query. The mutation patches that cache once and replaces the optimistic value with the server response.
Keeping a points useState in the top bar, another in the page, and a context copy. They drift as soon as one mutation fails or refetches.
onMutate: async (delta) => {
await queryClient.cancelQueries({ queryKey: accountKey });
const previous = queryClient.getQueryData(accountKey);
queryClient.setQueryData(accountKey, account => ({
...account,
points: account.points + delta,
}));
return { previous };
},
onError: (_error, _delta, context) =>
queryClient.setQueryData(accountKey, context?.previous),
onSettled: () =>
queryClient.invalidateQueries({ queryKey: accountKey })Trigger the bug. Then inspect the recovery.
These deterministic labs expose behavior that is usually invisible until production: optimistic rollback, out-of-order responses, and stale multi-window writes.
Available points
740The top bar and page are two observers of one server snapshot.
Both surfaces read the same cached account.
Trace the session before blaming the UI.
Authentication, API keys, authorization, and data policy are separate layers. Debug them in order.
The refresh token was not persisted back to the shared cookie, or concurrent refreshes rotated the same token.
Inspect in this order- Set-Cookie on refresh responses
- One SSR client per request
- Clock skew and token expiry
- Duplicate refresh calls across tabs
Use the SSR cookie adapter end to end, let one request refresh, then invalidate auth-aware queries when the session changes.
Safe to include in browser code. It identifies the application; a user token identifies the user. RLS must protect every exposed table.
Server only. It bypasses RLS and must never be sent to the browser or used with untrusted user-controlled authorization.
Move one state class at a time; preserve behavior while changing ownership.
- 01Inventory every value
Name its source, readers, writers, lifetime, and recovery path.
- 02Remove duplicate truth
Keep drafts local; replace copied server data with shared query keys.
- 03Harden writes
Add expected revisions, idempotency keys, rollback, and canonical reconciliation.
- 04Trace auth end to end
Verify cookie storage, server identity, domain authorization, and RLS separately.
- 05Test the failure order
Delay, reject, duplicate, reconnect, open a second tab, and expire the session.
Extend contracts, not conditionals.
New capability enters through one stable seam. Existing layers remain closed to unrelated details.
Extend the Zod enum and transition map; keep branching out of UI components.
Implement ExampleRepository and select it once in the composition root.
Reuse contracts and services, then give the surface its own composition and interaction model.
Add a typed recipe or semantic token instead of scattering conditional class names.
Evidence follows the architecture.
Test each responsibility at the narrowest useful layer. Select a card to see what it proves, what evidence to retain, and where the working example lives.
Domain
Domain policy testsProve business invariants directly against the service so policy stays correct without a browser, route handler, or database vendor.
Happy and rejected transitions, tenant isolation, deterministic scoring, revision increments, and stale-write rejection with stable error codes.
A typed contract, thin route, policy service, adapter-backed repository, explicit client state, failure UX, focused tests, reviewed screenshots, green CI, and a reviewable pull request.