UX Edge-Case Checklist

Make every UI feature state what it does when things go wrong before it counts as done.

moderate Testing & QA

What it adds

A required list of non-happy-path behaviours — failure, empty, loading, offline, permission, mobile, and accessibility — answered per feature.

What your agent is told to do

1
Attach the checklist to the point where work is proposed and to the point where it is reviewed, so the answers exist before the feature is built rather than being reconstructed afterwards.
2
Require a concrete answer for each category: what the empty state says and what it offers, what appears while data is loading, what the user sees when the request fails, and what a user without permission gets instead.
3
Make each answer an outcome someone else could verify. A feature that says errors are handled has not answered; one that says a failed save keeps the form open with the values intact and a retry has.
4
Insist on recovery, not just display. For every failure the checklist names, state how the user gets back to a working screen — retry, undo, a route out, or a preserved draft.
5
Do not treat the checklist as a fixed form to be filled identically each time. Cut the categories that genuinely do not apply, say why in a line, and add the ones this particular feature needs — a rigid template invites the same empty answers on every feature.

Edge cases it handles

Categories that do not apply must be marked as not applicable with a short reason, because a blank line and a considered exemption look identical once the feature has shipped.
Concurrency belongs on the list: two people acting on the same record, the same person acting in two tabs, and a second action fired while the first is still in flight all need stated outcomes.
Repeated actions need their own answer — a double-clicked submit, a held-down key, a rapidly retried request — and the answer is usually that the second attempt is absorbed rather than duplicated.
Recovery is the half most often skipped: showing an error is not handling it, and the checklist should be considered unanswered until the route back to a usable state is written down.
Vague answers are worse than none, because they pass review and provide no bar to test against — reject anything phrased as handled gracefully or shows a friendly message.
Offline and slow are different failures with different answers, and a feature that only considers the fully offline case will spin forever on a bad connection.
The checklist covers the shape of a feature's behaviour; a component's own internal contract belongs to Component Acceptance Criteria, and the two should not both try to specify the same keyboard handling.

Definition of done

Every UI feature carries answers for failure, empty, loading, offline, permission, mobile, and accessibility before it is built.
Categories marked not applicable carry a stated reason.
Each answer describes a verifiable outcome rather than a general assurance.
Concurrent and repeated actions have explicit stated behaviour.
Every named failure has a written route back to a working state.
The checklist is adapted per feature, with categories added and removed deliberately.
Review treats an unanswered or vague category as unfinished work.
The feature matches the existing design system.
No existing functionality is broken.

Related features

Interaction Test Harness

Theme Acceptance Criteria

Design QA Checklist

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.