States

States: State Machine Design

Design the $machine — the behavioral skeleton of a UXSpec. Every state is a promise to the user about what they can do and what they'll see.

When to Use

When building or revising the $machine section. Also useful for auditing an existing spec's state coverage.

Process

1. Map the Happy Path

Start with the ideal flow: entry → action → outcome. Define compound states (parents) and leaf states (children). Every compound state needs an initial child.

idle --SUBMIT--> loading
loading --HTTP_OK--> success

2. Map the Unhappy Paths

For every transition, ask: what else could happen?

• Network failure — timeout, server error, no connection
• Validation failure — bad input, missing fields, format errors
• Permission failure — expired session, insufficient role, rate limited
• Concurrent conflict — double submission, stale data, race condition

Each failure needs a state (or at least a handled transition) — not just an afterthought.

3. Cover All State Types

A complete machine accounts for:

• Empty — no data yet, no results, first-time use. These are onboarding opportunities.
• Loading — initial fetch, pagination, background refresh. Each may need different visuals.
• Error — network, validation, permissions, rate limiting. Each needs different copy and recovery.
• Success — confirmation, next steps, celebration. What happens after the goal is met?
• Partial — some data loaded, some fields valid. Don't force all-or-nothing.

4. Simplify

For each state, ask: is this truly necessary?

• Can two states merge? (e.g., "loading" and "refreshing" might be one state with a context flag)
• Is a state reachable? (orphaned states are dead weight)
• Does every state have a way out? (no dead ends)
• Look for the 20% of states delivering 80% of value.

5. Wire Transitions

• Map events to transitions with optional guards and actions
• Add entry/exit actions (set loading flags, clear errors, reset forms)
• Add invoke for long-running effects (HTTP calls, timers, polling)
• Use always transitions with guards for automatic routing (e.g., redirect if already authenticated)

Diagram

Present the state graph as text before writing JSON:

idle --SUBMIT--> loading
loading --HTTP_OK--> success
loading --HTTP_ERROR--> error
error --RETRY--> loading
success --RESET--> idle

Principle

A state machine is a contract: "in this state, these things are true and these things are possible." If a state doesn't change what the user sees or can do, it doesn't belong.