UI State Machine Pattern

Replace tangles of independent flags with one named state per interaction.

involved Developer Experience

What it adds

Explicit states and permitted transitions for the interactions that currently rely on several booleans at once.

What your agent is told to do

1
Find the interactions carrying three or more independent flags — submitting, loading, error, dirty, saved, disabled — and rewrite each as a single value that can only ever hold one named state.
2
Enumerate the permitted transitions rather than the states alone, and reject anything not listed. Most interface bugs of this kind are not a wrong state but a transition nobody expected, such as a response arriving after the user cancelled.
3
Drive every rendered detail from the current state — button label, disabled state, error text, focus — so there is exactly one place to look when the screen and reality disagree.
4
Trigger requests, timers, and navigation as effects of entering a state, and tear them down on leaving it, so a cancelled transition cannot leave a request or a countdown running.
5
This entry owns the shape of the machine. Where an interaction is a request-backed region, hand its states to Async Boundary Component for rendering rather than drawing loading and error treatments here.

Edge cases it handles

Combinations that should never exist — submitting and showing a success message, loading and displaying an error, disabled and pending at once — become unrepresentable once there is a single state value, and that is the point of the change.
Cancel, retry, and timeout are transitions like any other and must be enumerated. A retry from a failed state and a retry from a timed-out state may need different behaviour, and a cancel arriving mid-request must have a defined destination.
Effects belong to states, not to arbitrary code paths. A request fired from a click handler rather than from entering a state will keep running after the user has moved on and will write its result into a screen that no longer exists.
The current state must be readable from the outside for tests and for debugging, without inferring it from rendered text. A test asserting on a spinner's presence is testing the theme, not the behaviour.
A late response from a superseded transition must be discarded rather than applied, or a slow first attempt will overwrite the result of the retry that replaced it.
Do not model an entire screen as one machine. Several small machines that each own one interaction are easier to reason about than a single one with forty states.
Optimistic transitions need a defined path back — the state the interface returns to when the server rejects what it already showed as done.

Definition of done

Each converted interaction holds exactly one named state, with no residual independent boolean flags.
Permitted transitions are enumerated and anything outside the list is rejected.
Cancel, retry, and timeout are explicit transitions with defined destinations.
Requests and timers start on entering a state and are torn down on leaving it.
Responses from superseded transitions are discarded rather than applied.
The current state is inspectable directly by tests without reading rendered markup.
Rendering of request-backed states is delegated to Async Boundary Component.
The feature matches the existing design system.
No existing functionality is broken.

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How it works

1

Copy the link

Grab the Markdown instruction URL for this feature.
2

Give it to your AI

Paste it into Claude Code, Cursor, v0, Lovable — whatever you build with.
3

It inspects, then implements

Your agent reads your existing app first, then adds the feature to fit it.

Works with your stack

These instructions are written to adapt. They tell the agent to detect your framework, match your existing design system, and reuse what you already have — rather than assuming a particular stack.

Need it tighter than that? Customize the feature and tell it exactly what you're running.